Tom Saxton's Blog

Tesla Roadster Charging Rates and Efficiency

Tue, 20 Jul 2010 09:32:27 -0800

The Tesla Roadster offers a wide variety of charging options, from 120V/12A up to 240V/70A. Charging at higher voltage and current charges faster, but most of the time charging speed isn't an issue. If you drive a typical commute and charge at night, even the lowest power will get the car fully charged overnight. At least with the early Roadster firmware, charging at 120V was pretty inefficient because of the fixed charger overhead, but what about charging at 240V at various amperage limts? My theory was that charging at higher current is more efficient because you spend less time paying the charging overhead, but another owner challenged that assumption with the theory that higher current is less efficient because it generates more heat and thus increases the amount of energy spent keeping the battery pack cool.

Another aspect of charging is that for any given current setting, the Roadster will charge steadily at that current until it gets near the top of the charge, at which point it will start to taper off. This reduces your charge rate near the top of the pack. This aspect of charging isn't documented in the owners manual.

If I don't care about charging time, what's the best amperage for energy efficient charging? If I'm on a road trip and want to squeeze the most range out of time spent at a charging stop, how should I space my stops and how long should I charge at each one? I've collected enough data to shed some light on these questions.

Methodology

I performed a series of charges at various current levels from relatively low battery states up to a full standard mode charge. For each charge, I collected time, voltage and amperage once per minute, and state of charge once every 10 minutes. From that, I can compute energy used during every segment of the charge and the total energy used.

To track our energy use for driving, we have a dedicated electric meter for each of our EVs. To validate my energy calculations, I verified that the total energy calculated per charge matches the value computed from the meter readings.

All charging was done overnight in cool weather with a 2008 Roadster. The 16A charge was done with firmware version "3.5.17 15", all other runs were done with firmware version "3.4.17 15". The 16A charge stopped at a lower state of charge (96%, 188 IM) than I normally see (98%, 193 IM). I don't know if this is due to the lower current limit, the new firmware, or a one-time fluke.

Charging Efficiency Results

Is it more efficient to charge at a low rate or a high rate? Here are the results:

Charge Rate	Wh per Std %	Wh per Ideal Mile
16A	589	306
24A	544	282
32A	527	274
40A	512	266
48A	524	272
70A	516	268

As you can see from the table, there's not much variation in charging efficiency when charging at or above 32A, but energy use rises noticeably at lower current limits.

Road-tripping and Charging Rates

Also of interest are the charging rates at various current levels. This is especially important when charging away from home.

Charging at higher currents is faster than lower current, but by how much? Is it worth it to drive 55 mph in order to make it to a 40A charge point instead of driving faster and stopping sooner at a 24A or 32A charging spot? Tesla gives us a table on charging rates, but it's pretty low resolution.

How far can I charge before I start getting diminishing returns because of the current tapering that happens near the top of the charge? Tesla is silent on this subject.

If you care about getting the most out of your charging stops, you may be in Range Mode, so this table shows both standard and range mode values for when current begins to taper off.

Charge Rate	Ideal Miles per Hour	Current Tapering Begins At:
Charge Rate	Ideal Miles per Hour	Std %	Std IM	Range %	Range IM
16A	13	93	179	82	205
24A	20	94	180	82	205
32A	28	93	178	82	207
40A	36	93	178	81	204
48A	42	91	174	80	201
70A	61	84	161	75	188

Let's assume I want to get the most range for time spent charging, and don't need to charge all the way to the top. From the above table we see that if I'm charging at 48A or lower, I can expect to see the charging rate start to taper off at around 80% or a bit over 200 ideal miles (range mode). If I'm lucky enough to be charging at 70A on the road, my charge rate will start dropping around 75% or 188 ideal miles. I'll keep charging above 40A until I hit that 80%/200IM mark, so if my next charging stop is only 40A, I may as well keep charging to that point.

I'm sure there's some variation from car to car, and the pack and ambient temperatures will change charging behavior, so don't plan your trip to depend on these exact values, but this is at least a rough guide.

Charging Profile Graphs

Let's start by looking at how the state of charge varies over time using different charge limits. All charges are standard mode all the way up and normalized so that all the charge sessions are shown from the same starting point, around 36%. Note that the graph cuts off the last three hours of the 16A charge.

You can see how more current yields a faster charge, and that the rate of charge starts to drop off as the battery pack gets near the 100% mark.

Now let's examine current draw and state of charge throughout each of the current settings. In each session, the car draws an approximately constant amount of current until near the top of the charge when it begins to taper off. The following graphs show current drawn (in amps) and state of charge (as standard mode percent) as a function of charge time in hours. Each charge begins at a slightly different level, but all start below 40% so they have a nice long stretch of steady current draw.

You may notice that at 32A and 40A, the rate at which the SOC increases doesn't drop off as much as you might expect from how quickly the current drops near the end. I attribute this to the SOC calculation stabilizing near the end of the charge. It's difficult to know how much charge is in a battery while you're charging it. My guess is that the SOC is an estimate that gets better near the end of the charge. Regardless, the less current you're drawing, the less power you're putting into the battery. I've seen behavior that leads me to believe that if you stopped the charge within the tapering zone, you'll see the SOC continue to rise for a bit as the software gets a better estimate of the charge in the pack. However, you're still getting diminishing returns on charge time once the current starts to taper.

Another way to look at the data is to plot amperage draw as a function of state of charge. This will show us how the different charge limits compare with respect to when they start backing off from the full allowed current.

From this, we can see that there's isn't a penalty for charging at higher amps. Although it starts tapering the current earlier, it hits the lower amperage levels at about the same point as charging at those amperage values would start tapering.

Charging in Range Mode

Each of the above graphs show a standard mode charge. In range mode, it makes the bottom part of the charge range available and charges the pack even further: 0% and 100% in standard mode correspond to 11% and 87% in range mode. The same charging profile is in play, so as the battery pack crosses beyond the top of the standard mode charge, the current draw drops even further.

Tesla says that the range of the Roadster is 244 miles and that it can be charged from empty to full in as little as 3.5 hours, but those two don't really go together. The 3.5 hour charge time is for a full standard mode charge which is less than 80% of the full range, around 195 miles. Getting the full range mode charge takes longer. For my car, it's about an hour and forty minutes to go from a full standard mode charge to a full range mode charge (and add more time if you start below 10% in range mode). So, if you're on the road trying to make good time, waiting the extra 1:40 for another 25 ideal miles is not worth it unless you need the full range to get to the next charging stop. Charging to the top of range mode only makes sense if you're charging overnight and don't care how long it takes. So, on an extended road trip, a full range mode charge is probably only useful at most once per day.

Topics for Further Research

I would like to add data for some more scenarios, most notably 120V/12A (the slowest of the options, which requires three days for a full standard mode charge).

It will be interesting to see how these graphs change over time as the battery pack ages.

Charging in a hot environment definitely changes energy consumption during charging because the fan and A/C will kick on to cool the battery pack. It's harder to control for ambient temperature across multiple charges, but it would be interesting to collect data and see how things change. I would not be surprised to see a significant penalty for charging at higher current if that pushes the temperatures high enough to require the A/C during the charge.

These results are for our Roadster, yours may be different. Even the conversion from standard mode percent and ideal miles to range mode may vary between vehicles and across firmware updates. Drop me a note if you want to learn how to do this analysis for your Roadster.

Collecting and processing the data to produce the charts is only partially automated. It would be nice to automate more of the process to make it easier to do the analysis for me and others who are interested in doing the same for their vehicles.

Three EV Lessons for Nissan from Tesla Motors

Sun, 04 Jul 2010 13:45:00 -0800

In the all-electric Tesla Roadster, Tesla Motors has done an amazing job of designing and producing a car that shows the world how to build a great electric vehicle that is reliable and fun to drive, creating a driving experience that is far superior to that of a comparable gas-burning high end sports car.

Despite having Tesla's example, I'm concerned that Nissan is going to do a poor job with the Leaf. They've already made three missteps which I think need to be corrected before they start selling electric cars.

Overstating the Leaf's Range

Nissan has been saying the Leaf will have a 100-mile range, but they are basing this claim on the LA4 city driving cycle, not on a highway or combined cycle. Tesla says the Roadster's range is 244 miles, and that's a real number. If I drive 55 mph on level freeway, I get energy use consistent with that 244-mile range. From what Nissan has said, I suspect that going 55 mph on level freeway with no heat or A/C will yield somewhere around 80 miles. That's still an awesome range that will meet the needs of many drivers, but it's a disappointment that they entered the game by overstating their range with a number that requires driving even more conservatively than a steady 55 mph.

The vast majority of people who've had the opportunity to drive electric on a daily basis prefer it to driving gas. The only people I've heard of complaining about the electric driving experience are people who purchased an EV with inadequate range for their driving needs. The EV consumer has to take some responsibility to understand their real driving needs and the capability of the EV they are considering purchasing, but any automaker that does anything less than conveying a conservative and realistic picture of the car's capabilities is going to end up with a lot of unhappy customers and a public relations disaster.

Nissan: Get real range numbers out there now. Tesla Motor's detailed page on range information could be better by being far more visible on their site. Make sure the one or two numbers that are most visible to the public are representative of what consumers can realistically expect to get under conditions that are clearly stated. Beyond a simple number or two, also put lots of technical detail out there to satisfy the people who want all of the information and will be the early adopters that clear the path for the mainstream buyers.

Update: I arrived at the 80 mile figure by adding a generous 10% to the 70-mile range for 55 mph with A/C on as reported by Forbes. A MotorTrend article pointed out by mwalsh and evnow on the MyNissanLeaf forum after I published this post quotes Nissan Leaf chief engineer Hidetoshi Kadota as saying normal freeway driving at 60-70 mph without climate control yields a range of 105 miles. So maybe the Leaf's range is better than suggested by the negative Forbes article, but it's still the case that Nissan is not making any of this information available on their web site.

Not Fully Exploiting the Advantages of Driving Electric

Nissan is apparently making the Leaf drive like a gas car rather than fully exploiting the advantages of driving electric. Specifically, they are putting little or no regenerative braking on the accelerator pedal. Tesla does a beautiful job on this. As you press down on the accelerator pedal, the car accelerates more, just as you'd expect. As you let up on the pedal, you get to the point where the car is just coasting before the pedal is completely released. As you release more, the car starts using the motor as a generator to charge the battery, the more you release the stronger the effect. When the pedal is fully released, the regenerative braking becomes quite strong and will slow the car down almost to a stop. (This effect is stronger at slow speeds where you're likely to want to slow more quickly, and lighter at freeway speeds where you want a more gradual slowing to match traffic.) To slow the car more quickly or bring the car to a complete stop, you press the brake pedal to engage the car's friction brakes, just like driving on gas.

After getting used to driving a 2002 Toyota RAV4-EV, which puts only a little regenerative braking on the accelerator with more on the brake pedal, I was dubious of the Tesla scheme. (The Honda Insight and Toyota Prius are similar to the RAV4-EV in this regard.) After driving the Roadster for a few days, I found the Tesla scheme to be much better than the RAV4-EV. It has two big advantages over more closely emulating a gas-burner. For the sake of driving efficiency, I want to slow the car with regenerative braking as much as possible, every time you touch the friction brakes you are wasting energy by converting momentum into heat and brake wear. With the Tesla scheme, I know exactly when I switch from efficient regenerative braking to wasteful friction braking: when my foot moves from the accelerator to the brake pedal. Aside from helping me drive more efficiently, and reducing wear on the brake pads, the Tesla scheme is simply a better way to drive. I can control speeding up, maintaining speed and slowing down all with one pedal. With just a little bit of time behind the wheel, it quickly becomes a more natural and comfortable way to drive. This is especially nice when driving downhill, it's just so easy to control your speed, driving a gas car seems primitive. The only complaint I've ever heard from a Tesla owner about how this works is that they want more regenerative braking on the accelerator, enough to fully stop the car at a light. Personally, I think what Tesla has done is perfect: the mostly one-pedal driving is familiar enough that a first time driver won't have any problem driving the car, with a bit of practice it's a better experience, and the occasional use of the brake pedal keeps my brain-foot connection trained to use both pedals, reinforcing the old skills that puts your foot on the brake pedal instantly when required to slow or stop quickly.

Nissan: talk to some Roadster owners about the pedals. Drive a Roadster for a week or a month. It's important to get this right, it will give your owners a great driving experience sell a lot of cars.

Yielding to Unreasonable Demands for Artificial Traffic Noise

Nissan has yielded to the hysterical calls to add noise to electric vehicles. So far, Tesla Motors has resisted doing the same. All modern cars are quiet when driving slowly; the difference between a pure-electric car and a modern sedan is only audible in very quiet conditions. If quiet cars are a safety issue, then we should be looking at requiring all cars to make a minimum amount of noise at low speeds rather than singling out electrics and hybrids. There is no credible research to suggest that quiet cars are any more dangerous than other cars. Cars are only quiet at low speeds, when both drivers and pedestrians have enough time to react and avoid any problems.

Even if we make electric vehicles noisy at low speeds, they will still be inaudible in noisy environments. If anything, noisy cars that drown out the normal sounds of tires, fans, and pumps are more of a danger than quiet cars. So, if we're really worried about sound-related risks between automobiles and pedestrians, we should have strict laws for all cars that require minimum sound levels at low speeds, and prohibit sounds loud enough to drown out those minimum sound levels. But actually, that wouldn't help either. Just imagine what a parking garage would be like if all cars had to make a constant continuous sound, it would be like having a stadium full of vuvuzelas creating a cacophony that makes it impossible to discern any individual sound while training everyone to ignore the annoying buzz.

Instead of squandering an opportunity to have quieter cars, we should be taking real steps to improve safety for all pedestrians, bicyclists, and everyone else on the road. We should be studying the whole situation to find out if quiet is a real problem for pedestrians, considering all cars -- not just electric and hybrid -- and also the impact of natural or artificial traffic noise on quality of life. Does adding noise to all cars benefit anyone, or does it just crank up the level of background noise and make it harder to hear what's going on nearby? Does adding a constant warning noise to a car just train drivers to expect that pedestrians will automatically scatter out of their way?

I've been driving electric for two years and I have surprised exactly one pedestrian: a woman who was walking backwards into the driving lane of a parking lot while carrying on a conversation with someone across the lot. I stopped and waited for her to realize she was walking into an occupied traffic lane and she eventually saw us waiting for her. She was surprised, but I wasn't, and there was never any danger to anyone. She was clearly embarrassed by what she had been doing and tried to blame her reckless behavior on my quiet car. If I had been going fast enough that her foolishness could have created a dangerous situation, my car would have been making the same tire noise as any other car, which may or may not have been audible depending on the environment.

I'm quite sure that I don't need my neighbor's electric car waking me up at 5 am just because people are scared of unfamiliar technology. I propose that we solve a real problem, like driving while phoning or texting, before we rush into squashing a quiet car advantage in response to uninformed hysteria.

Nissan: Please give your drivers a manual way to alert pedestrians with something less obnoxious than a blast of the car horn. GM did this with the EV1 and owners loved it. Hold off on making a constant noise until there's enough research to show quiet cars are a danger and we have a validated way to improve the situation for all cars -- electric, hybrid, or gas-burning.

Edited July 5, 8:46 am: corrected technical error in description of Tesla's regen algorithm and clarified pedestrian surprise story.

Edited July 5, 3:20 pm: added update on more optimistic Leaf range numbers as reported by MotorTrend.

Electric Vehicle Range and Charging

Thu, 24 Jun 2010 22:34:40 -0800

If you are interested in driving an electric vehicle, I'd like to tell you how to ensure that you'll have a great experience, or at least make sure you don't have a disappointing experience.

Here's the secret formula for EV success: make sure the range of the vehicle suits the driving you plan to do with it. I know that sounds pretty obvious and easy, but there are two big barriers to success: bad reporting in the media and obfuscation by the automakers. There's also a bit of complexity: just like gas mileage, you can't express EV range with a single number. I'll get that all straightened out from the perspective of someone who has been driving all electric for almost two years.

In addition to the general facts of driving electric, we recently got some more specific range numbers for the upcoming Nissan Leaf which I'd like to put into perspective for potential buyers.

Reporting the Obvious and Irrelevant

If you follow EV coverage in the press, you'll find a steady stream of articles from reporters who think they've discovered the flaw that will deflate all of the hype about EVs. Their basic premise is that EVs won't work because they take too long to charge and there's nowhere to charge them. These articles are either totally made up, or based on the bad experience of a single EV driver and don't represent the real experience of the majority of EV drivers who purchased a vehicle appropriate for their needs. My purpose here is to make sure you don't become the excuse for some lazy reporter to write yet another of these uninsightful articles.

Would a newspaper publish an article about a Ford Focus owner who was disappointed that he couldn't fit his wife and seven kids in the car? How about a Honda Civic owner who's mad her car isn't suited for towing an RV? A Hummer owner who's mad about how much it costs to drive a mile? Of course not, these would be laughably obvious mistakes made by the owner in choosing a car.

For the consumer properly informed on the benefits and limits of electric vehicles, it's equally obvious that buying an EV with a 75-mile range to do a daily 74-commute with no charging infrastructure isn't going to yield a happy driver. That's obvious and boring.

The real story is that there is no problem with range or lack of charging infrastructure if you can just charge at home to meet your driving needs, instead it's a real convenience not to have to fuel your car away from home. So let's see if you qualify...

The Rule

To be a happy EV owner today, you want to buy a car that has enough single-charge range to handle all of your daily driving with a reasonable buffer for typical errands without needing to charge anywhere other than your charger. (Your charger is probably installed at your home but might also be at your work location.)

The good news is that for most drivers, the required range is surprisingly low. A 2003 US Department of Transportation survey (PDF) found that 78% of Americans drive less than 40 miles a day. If you're in the 78%, and don't often have big exceptions to that daily commute distance, then an EV that gets at least 70 miles of range in your driving conditions will most likely make you one happy camper. (But keep reading to learn how to evaluate EV range.)

Starting this fall, we'll start to see a lot of chargers getting installed in a few metro areas in the US and other countries. As this happens, and EV ownership goes up, more and more charging will become available and convenient. As that happens, charging away from your home charger will become more dependable and the usable range of EVs will expand as a result. For example, if you can charge at home and at work, then the usable range of an EV is doubled because you only need to travel one way on a single charge (with a reasonable buffer).

Since there's going to be limited availability of affordable, practical, freeway-capable EVs in the near future (as in zero today, and a few thousand Nissan Leafs starting to trickle out starting in December of this year, then more from other automakers to follow), it's OK if the first few models of EVs don't work for you, they will work for millions of potential buyers. Wait for an EV that will be right for your driving needs.

The Win

After you've driven electric for a month, spending just a few seconds to plug in each night to start every day with a full charge, without ever having to stop at a gas station, you'll wonder how you ever tolerated the hassles of driving a gas burner.

In addition, the experience of driving electric is just better: you get instant acceleration without waiting for the engine to rev up and the transmission to shift, another nuisance of driving gas that you'll only notice when you get used to driving without it.

Bonus: no tailpipe emissions, low-to-zero emissions from electricity generation, and never having to worry about the price at the gas pump.

Evaluating EV Range

Just like gas mileage, EV range can't be expressed as a single number. Even the two EPA city and highway gas mileage numbers you see on vehicle stickers don't tell the whole story. This is such a big issue with gas cars, the caveat "your mileage may vary" has become part of our cultural vernacular.

Let's start by going over how gas mileage works. Those gas mileage numbers on the sticker in the window are determined by driving the car on two standard EPA driving profiles meant to simulate typical driving conditions, which have been recently revised to better represent actual driving conditions by including things like using air conditioning on part of the cycle.

Gas mileage depends on a number of factors, including passenger and cargo weight, HVAC use, start/stop frequency, road incline, rain/snow, and so forth, but the biggest factor is speed. At low speeds, gas mileage suffers because there's an overhead of running/idling an engine that burns fuel whether you're moving or not. Stop and go traffic is also bad news, because you invest energy in speeding up only to throw all it all away by converting your car's momentum into heat plus wear and tear on your brake pads. At higher speeds gas mileage suffers because wind resistance goes up rapidly with speed, so much so that it takes more energy per mile in a way that starts increasing dramatically at the low end of freeway speeds. Somewhere in the middle, at a moderate, steady speed, is where you get your maximum gas mileage.

Electric vehicles behave similarly, except they get punished less in stop and go traffic because, like hybrids, they can slow down with regenerative braking wherein the motor is driven by the drivetrain to act as a generator to put charge back into the batteries. This not only improves energy efficiency, but also reduces brake wear.

Given this complexity, how can an automaker tell you how your gas or electric car will perform under your driving conditions? Answer: they can't.

While you can argue that it's even more important to understand energy efficiency (in the form of single-charge range) for an electric vehicle, there's the ugly truth about burning gas that no one likes to talk about: it's no good for predicting long-term fuel costs. With a proliferation of gas stations everywhere, range isn't something you think about for a gas car. What you do think about is your pocketbook. Better mileage means cheaper stops at the gas station. While knowing your gas mileage might tell you what you'll be spending at the pump this month, it doesn't say anything about what you'll be paying next month or next year. Anything from a hurricane, to Wall Street speculators, to a political action by OPEC, to the whim of some oil nation tyrant can cause gas prices to double by barely nudging the precarious balance between world oil supply and demand. Electricity rates are far more stable, especially when it comes from renewable sources that aren't subject to the unpredictable economic forces that rule the world's fossil fuel energy market.

How can a potential buyer figure out if a given EV has the range required to convert from the hassles of driving gas to the joy of driving electric? Read on...

Case Study: the Range of a Tesla Roadster

For most people, buying a $109,000 two-seat sports car is totally out of the question, whether it's a gas-burning Ferrari or an all-electric Tesla Roadster. Being able to go from 0 to 60 mph in under four seconds isn't going to get the kids to school or bring home the groceries from Costco. But, as of this writing, Tesla Motors is the only automaker selling a production, freeway capable electric vehicle in the US. If you dig a little, their web site provides a wealth of information about driving electric that will be of help to any potential EV driver.

The best illustration I have found of the effect of speed on efficiency, and thus range, is this graph from Tesla Motors showing how the Roadster's range varies with speed, while holding other factors constant at favorable values (constant speed, no AC, no driving up a mountain, etc.).

The EPA range number for the Roadster is 244 miles. From the graph, you can see that you get that range driving at about 55 mph. If you have to pick one number to describe range for a Roadster encompassing city and highway driving, this is a pretty good choice, and it's a real number that I've personally verified as much as possible without actually driving the car until it stops. Likewise, the value of about 180 miles for 70 mph matches my real-world experience. Simon Hackett and co-driver Emilis Prelgauskas came close to the graph's 34 mph range number by driving 313 miles on a single charge in Australia last year. Perhaps someone will be patient enough to try out the 17 mph peak on the graph at over 400 miles of range, but that would be a very long drive!

I'd say Tesla did a good job here, picking a reasonable single number for stating range based on some combination of the EPA city and highway cycles. They also provide the graph showing the whole story, at least with respect to speed, although to find it you have to dig down into their blog entries to find the article with the graph and full explanation.

But there's a bit more to the story that requires more digging. The above range numbers are for using the entire battery charge from full to empty, something you really don't want to do on a regular basis because it's not good for the life of the battery pack. For normal daily driving, you don't need 244 miles of range, so Tesla provides a "standard" mode of charging that only uses the middle 80% of the battery pack. This will extend the life of the battery pack and still give you 200 miles of range at 55 mph, or about 160 miles at 70 mph. This is between four and five times what most of the drivers in the US need for their daily commute. For daily driving, the range of the Roadster is ridiculously high. Going on a road trip beyond the single charge range is doable, but it requires patience and planning. This situation will get a lot better as high-speed charging stations start to appear later this year.

The numbers also get worse in really hot weather. Last summer I drove from Portland to Seattle in 100-degree weather, about 180 miles. This trip is easy at 55, in fact even at 65 mph it's no problem. But this trip, with the HVAC system using energy to keep the battery pack cool, it took getting off the freeway and careful route planning to reduce both distance and speed to get home without having to stop for a partial charge.

The upshot: if you live in an extreme climate, with either a lot of sub-zero winter days or 100+ degree summer days, you'll want to add more buffer to your required EV range.

The last big issue is aging of the battery pack: as the battery pack ages, its capacity will decrease gradually over time, then drop more rapidly as the battery pack wears out. Our car is performing the same as it did when we got it one year and 9,000 miles ago. Other Roadster owners have crossed the 20,000 mile mark, and so far I haven't heard of anyone noticing a loss of range. Tesla's battery pack warranty is only 3 years or 36,000 miles, which is in line with other high performance sports cars, but is a bit underwhelming compared to their statements of expected battery life, seven years or 100,000 miles. Nissan says their battery pack should last 10 years, and because the Leaf is a much more mainstream vehicle I expect they will offer a much better battery warranty.

Still, if you're planning to drive your new EV for 5 to 10 years, it's not going to be smart to buy an electric car that's right on the edge of meeting your needs with its full factory-fresh range.

Our Electric Garage

In July of 2008, while we were waiting for Tesla to build the Roadster we reserved in 2006, we were fortunate enough to buy a rare 2002 Toyota RAV4-EV from its original owner in Berkeley, CA. If you've seen Who Killed the Electric Car, then you've know what a great electric driving experience the lucky few drivers had during the brief period where California required all of the automakers to find a way to reduce tailpipe emissions to zero.

When we got the RAV4-EV, we expected it would take care of about half of our driving. We were wrong by a wide margin: it took over 95% of our driving. The only time we burned gas was when we each had to be different places at the same time. Despite our EV enthusiasm, we were range anxiety victims and overestimated how much range our driving really required.

In our experience, the RAV4-EV gets about 100 miles per charge. Even staying out of the top 10% and bottom 20% of the battery pack means we can drive 70 miles per charge under our typical driving conditions, and can handle any driving conditions with enough range we don't generally have to think about it.

When our Roadster finally arrived nearly a year later, we were totally converted to the electric driving experience. Having a second electric car meant we didn't have to choose which of us got to drive the smooth, quiet car.

Our hope is that the Leaf will bring this sort of EV capability into the mainstream in an affordable, practical, safe vehicle.

Nissan Leaf Range Numbers

The first range number we heard for the Nissan Leaf was 100 miles using the EPA's LA4 drive cycle. Darryl Siry gets credit for being the first to point out that the LA4 drive cycle is a poor choice for describing EV range as it's a city driving cycle that's nicer to the range than the combined city/highway drive cycle that is used by Tesla. Siry also wrote a great piece on the issues with range numbers and the need for federal regulations on how they are reported which added perspective to my personal experience and helped inform my writing here.

On June 19th 2010, we got some more range numbers from Nissan via Forbes. To summarize:

Cruising at 38 mph in 68-degree weather: 138 miles.
Suburban traffic averaging 24 mph, 77 degrees: 105 miles.
Urban highway, 55 mph, 95-degrees, A/C on: 70 miles.
Winter city driving, 14 degrees, averaging 15 mph: 62 miles.
Stop and go urban traffic averaging 6 mph, 86 degrees, A/C on: 47 miles.

The Forbes article is typical anti-EV fear mongering, the facts presented with pithy commentary but no critical analysis. Have you ever read an article on how your gas mileage drops in stop-and-go urban traffic during the heat of summer or the cold of winter and how much that's going to cost you when you're driving your gas-guzzling SUV? Of course not. But you do hear about how it will affect the range of an EV that isn't even on the roads yet. It's great to get more facts, but try to ignore the hand-wringing hysteria that makes it sound like the federal government is about to repossess all of the gas burners and force everyone to drive a Nissan Leaf.

The fact is, the Leaf doesn't have to meet the needs of every driver in the US. It just has to meet the needs of the few thousand people lucky enough to be able to buy one in the next year. Even that worst-case 47 miles is going to be good enough for millions of drivers now (remember that 78% of US drivers commute less than 40 miles per day) and good enough for even more drivers when there are convenient chargers at workplaces and malls.

Is the Leaf's Range Right for You?

I think the best way to figure out what range an EV needs to have to suit your needs is to monitor your driving. Just write down your odometer when you get home each night. From that, you can figure out how far you actually drive. Be sure to get not only your regular daily commute, but also some examples of exceptional days with extra appointments, shopping, detours, etc. If you have an additional vehicle that would supplement your EV, throw out any long drives that you would choose (in advance) to handle with that vehicle. Then add a buffer for the unexpected, and, if it applies, more buffer for the extreme driving conditions that reduce range.

People who haven't driven an EV will be tempted to always have half of the battery in reserve for surprises, but most experienced EV drivers are very comfortable driving down to 30% or even 20%. (With the Roadster where I get great feedback on the state of charge and know it won't hurt the battery, I have no problem driving down to 10%. With the RAV4-EV, which gives less precise info, we try to stay out of the bottom 20%.)

If you commute 70 or more miles per day in a city that regularly has horrible traffic, freezing cold or sweltering hot days, and isn't planning for charging infrastructure, then don't buy a Leaf to be your only car this year. Wait until the cars and the charging better suit your driving needs. There are more than enough of us to buy up every single Leaf Nissan can make in the next 12 months, so don't become fodder for another annoying article about how EVs are impractical because someone bought one that's not suited to their driving.

If the Leaf's range numbers do suit your driving needs and you want to get an early start driving electric, then sign up, right now. They are going to sell fast. But before you fully commit to a purchase, get the information you need to determine if the Leaf will meet your needs, and get that info directly from Nissan. Don't depend on a conversation with your local auto sales drone.

I'm glad we have learned more about the Leaf's range months before anyone will be committed to buying one. Next up I want to see a graph like Tesla gives for the Roadster range vs. speed under optimal driving conditions. I also want to know if the range numbers given are for using the full battery to its maximum range, or if they include allowance for the reserves at the top and bottom of the charge cycle needed to maximize battery life.

If the Leaf will meet your needs, you won't regret switching away from gas. The benefits of charging convenience and drivability are great motivators to be among the early adopters to buy one of the first mainstream factory electric vehicles.

Track Day at Pacific Grand Prix

Sun, 21 Mar 2010 10:34:00 -0800

On March 17, six Seattle-area Tesla owners joined the Evergreen Lotus Car Club for a track day at Pacific Grand Prix, the new smaller track next to Pacific Raceways in Kent, WA. The folks at Pacific Grand Prix were excited to have a bunch of Tesla show up. We were treated to unseasonably nice weather, clear and sunny except for a brief hail storm.

Trevor Cobb of the ELCC did a wonderful job of organizing the event and we really appreciate his invitation to the Tesla cousins.

(photo courtesy of David Caley)

The track is 30 feet wide and 0.8 miles long. It's used for go cart rentals as well as track days for full size cars. As you can see from their web page, the track is all about turns with just a couple of short straightaways, so the speeds are kept under control. There were no timers on the track, so it was all about learning the track and improving your own driving. I did some autocrossing in the mid-90's, so this was somewhat familiar territory, although less forgiving of big mistakes. (The day went fine, the only notable off-course driving was a Lotus driver who sprayed dirt all over the track with no harm done to car or driver.)

A couple of months ago, the Pacific Grand Prix folks attended a Seattle Electric Vehicle Association meeting to let the community know they are supportive of EVs. At that meeting, Daniel Davids, long-time local EV advocate and now president of Plug-in America, offered up some tips to the group from his extensive track-driving experience. So, when I got the email from Trevor inviting the local Tesla owners to join in on their track day, I offered to Daniel that we could split the driving if he'd give me some pointers. He accepted.

We arrived at the track at 8:00 am, drivers meeting at 8:30 and the first group hit the track at 9:00. The second group was the six Roadsters. We got 15 minutes of driving, then about an hour wait between runs.

I took the first run and Dan talked me through it, helping me to improve on each lap. Between runs Trevor offered up some helpful tips also. On the second run, Dan showed me what a Roadster can do with a skilled driver behind the wheel. It was a little frightening at first, then I could see that he knew what he was doing and that I was in a for a real treat. Dan just swept through the turn combos where I was struggling with the steering wheel. He made everything look smooth and easy, except for figuring out how the passenger is supposed to hang on through all of that lateral acceleration without a steering wheel to grip. After seeing it done well, my run in round 3 was greatly improved.

Depending on the driver, each run was consuming between 3 and 7 ideal miles per driven mile. On my first tentative run, I used 21 ideal miles in 7.5 actual miles. Rich, an accomplished track/autocross driver, used 36 ideal on that same run. Dan managed to burn 35 ideal miles on the second run, even though he exited the track after only 5.2 miles.

It was also fun to compare the recent energy use screens between me and Dan. Here's mine after the third run:

You can see I averaged 761 Wh/mi over the last five miles after the cool down lap and exit from the track. In normal driving, the average is more like 260 Wh/mi, with occasional green spikes for acceleration, but here it's solid green with dips for occasionally getting off the pedal. Doing the math from the trip meter says I used 841 Wh/mi for that run. Now, here's Dan's graph from the second run:

There is no letting off the pedal for Dan, at least not for long enough to show up on the graph, and the graph is pegged at 999 Wh/mi. Doing the math from the trip meters says Dan averaged 1,423 wH/mi on that run.

There was supposed to be 240V charging at the track, but there was a problem with that circuit, so we searched out all of the 120V outlets around the track and charged as much as we could. Even with that little charging, I had plenty of charge for the 25 miles home when I had to leave around 3:00, I could have easily stayed for the last run. Others who had a longer drive were charge constrained and had to leave early. The track folks are very open to getting better charging installed, so future events should be easy for everyone.

Birthday Puzzle Treasure Hunt

Mon, 14 Dec 2009 10:51:41 -0800

Cathy and I are both puzzle nuts. We have two daily puzzle calendars to jump start our brains during breakfast. Cathy has a diverse taste in puzzles and is frequently working her way through a book of Japanese puzzles while I'm reading the newspaper at night. I'm not talking about Sudoku, she chews through puzzles like Kakuro and Hanji.

In addition to solving puzzles, she also likes to create puzzles, which is much harder and far more time-consuming than solving them. Quite often, I get a sequence of puzzles on my birthday each of which has an embedded clue to the next puzzle, eventually leading to my birthday gift.

This year we were extremely busy for the two weeks leading up to my birthday. We spent a week in Hawaii prepping our condo for a new rental agency, then spent the next week being EV groupies attending all of the Nissan Leaf events in Seattle, then on Saturday Cathy was the head judge at the Washington State FIRST LEGO League Championship. Anyway, we were busy and I was sure Cathy didn't have time to create any puzzles.

So, I was quite to surprised to find a puzzle sitting on the bar at breakfast. I like doing Marilyn vos Savant's Numbrix puzzles that accompany her column in Parade magazine, so Cathy created a jumbo size version. This is probably the only puzzle format for which I am more practiced at solving than Cathy, but she still managed to create a puzzle in that format, larger than normal, challenging for the type, and yet still solvable.

It was a good puzzle and I enjoyed solving it. If you want to try, download this PDF version. When I was done, I was amazed she had created such a nice puzzle and couldn't imagine when she had time. I wondered if it was the first clue of a treasure hunt, but I didn't want to assume it was and have her think I was disappointed to have just a single puzzle. I also couldn't imagine how solving a Numbrix could yield a clue to another puzzle. While all of this was running through my brain, she was giving me the look that says, "you're not done yet." Stop reading now if you want to try to find the clue to the next puzzle without a hint.

While I was solving the puzzle, I realized that sometimes when I work these puzzles, instead of writing in the numbers, I just draw the path through the sequence connecting the centers of the boxes in order. It actually occurred to me that might be interesting, but I couldn't imagine how that could yield a message. Cathy realized that by drawing lines in the manner I described, there are 7 letters that can be easily formed: CEHISUY plus maybe a couple of others like T and L that might work but leave odd shaped areas to be filled to complete rectangular blocks. If you solve the puzzle then draw the sequence line you'll see a word that told me where to look for the next puzzle.

If you'd like to try working this one on paper, download the PDF version. Four of the clues require a bit of inside knowledge, but it's probably doable anyway. Stop reading now if you want to try it without any hints, if you perhaps know the cars we drive, enjoy shows at the Village Theatre and were an applications programmer at Microsoft in the 1990s.

1 Down is a reference to the Hungarian naming convention used by some programmers at Microsoft where "max" means "one more than is allowed." This photo of one of our cars will give you the answer to 4 and 6 Down. 25 Down is a reference to a line in Chasing Nicolette, but you can probably get it from the other clues without knowing the show.

After solving that puzzle, you can find another hidden clue that told me where to find an envelope containing my birthday gift: a signed print of this xkcd comic which is an alarmingly accurate a description of what Cathy has to deal with all too often.

Tesla Roadster Energy Reporting and Efficiency

Sun, 13 Dec 2009 19:02:06 -0800

For the month of November, I drove the Roadster 762.2 miles. That's mostly with just me in the car driving a variety of city and highway miles. I tend to drive enthusiastically most of the time, but the month also included a roundtrip drive to Longview, WA on cruise control at 55 mph.

During the month, I put about 247.8 kWh into the car from the wall (213.3 kWh metered from my garage plus approximately 34.5 kWh from an unmetered NEMA 14-50 outlet in Longview). That's 325.1 Wh/mi and includes charging losses, battery pack self discharge, heater, headlights, etc. That's my wall-to-wheel number and is based completely on things I can measure.

From July 25th to August 27th, I drove the Roadster 696 miles and pulled 234 kilowatt hours (kWh) from the grid, giving us 336 Wh/mi. That included some hot weather and four 1/4 mile runs at Pacific Raceways.

On individual charges, I see efficiency vary from 240 Wh/mi to over 400 Wh/mi, and obviously much higher for things like drag racing.

I charge consistently at 240V and 40A at home. In Longview it was 230V and 40A. Because of charging overhead, I assume I would get slightly better charging efficiency if I charged at home at 70A. So, my numbers are just that, my numbers. Another driver would get different numbers depending on driving, weather, road conditions, and charging habits.

The EPA estimates documented in the paperwork for our car say 260 Wh/mi city and 290 Wh/mi highway. I've seen information from early 2008 Roadsters that had the EPA numbers and 340 and 360 Wh/mi.

You may have heard Roadster owners talk about numbers well below my 330 Wh/mi numbers. These are most often the number reported by the car's info screen which are not wall-to-wheel numbers, and in fact are (as far as I know) not at all documented as to what that number means. I have figured out some things about the numbers reported by the car, which I'll now explain.

For the month of November, the Roadster's trip meter says that I used 207.9 kWh, and thus 272.8 Wh/mi. But what does that mean? Did I push 207.9 kWh into the motor, or is that net of energy pushed back into the pack from regenerative braking (regen)? Does it include energy used to run the accessories and/or running the coolant pump and fans during charging?

On the "Energy History" screen, the Roadster tells me my "net energy used" for the month was 233 kWh and that I got 26 kWh from regen. What does "net" mean? I would assume that "net" means "net of regen," i.e., power from battery pack minus power into battery pack from regen. Except, if I compare those numbers to what the trip meter says, I notice that 233 - 26 = 207, which is suspiciously close to the energy use number reported on the trip meter.

From that, I infer that the trip meter's number is net energy use from the battery pack (power drawn minus regen put back in), and thus the so-called "net energy" from the energy use screen is really the gross energy pulled from the battery pack including energy that went into the pack from both wall charging and regen charging.

Do these numbers include the energy spent on accessories? Is the difference between what I put in through charging (247.8 kWh) and the car's reported net energy use (207.9 kWh) just charging losses or does that also include accessory use? I have no idea.

The only number I can stand behind, and the only number I can compare with other electric vehicles, is the wall-to-wheel number. The efficiency number reported on various of the Roadster's info screens is useful for understanding how driving style and conditions affect efficiency and for predicting/optimizing range, but is seemingly useless in any other context.

I believe the same is true of any efficiency number for the Leaf given out by Nissan, or any other EV manufacturer or driver, unless that number is as clearly defined and directly measured as the wall-to-wheel number.

It used to be that the Tesla screen reported an energy number after each charge that was much lower that what was actually drawn from the wall. I suspect that was the energy that actually made it into the battery pack, but I never saw it defined by Tesla. More recent firmware versions are reporting a number that is close to the number I read from the wall meter (and averaging multiple consecutive readings together agrees to within 1% of the wall reading). This is a big step forward for drivers who want to monitor their actual wall-to-wheel energy use and efficiency, but don't want to go to the expense of installing a dedicated meter. It would be a real benefit to the Tesla community if Tesla would (a) define the number they currently report and (b) make the energy drawn from the wall across multiple charges easily available.

Regarding range on a single charge, my personal record is 192 miles driven with a passenger in 100+ degree weather starting with a bit less than a full charge and ending with 10 miles of range left. On the trip back from Longview in cool weather, I drove 136.9 miles using cruise control at 55 mph using 55% of the battery. To the extent that you can extrapolate that to the full battery, that figures out to about 249 miles of range. On the trip down to Longview earlier the same day, also using cruise control at 55 mph, it was raining and colder, so I had the wipers, headlights and heater on and used 65% of the battery pack, for an extrapolated range of 208 miles.

My car is a 2008 Tesla Roadster with firmware version "3.4.15 15" (upgraded from "3.4.13 15" on 11/15/2009).

Edited at 10:23 pm on 12/13 to correct typo in second paragraph.

Nissan Leaf Test Drive

Wed, 09 Dec 2009 20:50:50 -0800

Today, Cathy and I both got to drive the Nissan Leaf test vehicle, apparently a Nissan Versa outfitted with the Leaf's drivetrain. Coincidentally, last week we rented a Versa on vacation, so we were treated to a virtual side-by-side test of gas versus electric. They had a course laid out with cones in a parking lot, which I treated as a small autocross course. The test vehicle handled well and had good pick-up, better than the gas-burning Versa.

Most interesting was how quiet it was. The Roadster has a loud gearbox whine when accelerating, plus road and wind noise. The whine is much quieter than a gas engine doing similar acceleration, but it's not silent. The RAV4-EV has a comparable road noise level, maybe a few dB below the Roadster and minus the loud drivetrain whine. Both the Roadster and RAV4-EV are about 7 to 8 dB noisier than Cathy's parents' Honda Accord doing 60 mph on the same section of average freeway surface. (We measured all three vehicles with a Radio Shack sound level meter.) The Nissan test vehicle was very quiet from the inside, I think quieter than the Accord, but we didn't do any measurements. From the outside, you hear the same tire sound you hear from any decent modern sedan.

Before buying, I'd want to take it for a real test drive, get it up to speed on the freeway, etc. That said, based on our test drive today, I'd highly recommend it to anyone who is an early adopter, very interested in driving an all-electric family sedan, and whose driving habits could be met by the Leaf's range.

That assumes that Nissan doesn't bungle the whole thing by forcing buyers into some ludicrous over-priced battery lease.

Sammamish to Mt. Rainier

Wed, 23 Sep 2009 14:36:47 -0800

On Monday, the weather was too nice to not be out driving so I decided to take a spin up to Mt. Rainier to see if the roundtrip could be done on a single charge. Thanks to Todd Laney for planting the seed by suggesting it as a possible Roadster owner drive route to follow our adventure on Sunday.

I used Google maps to plot a route and get mileage/time estimates. Google estimated the drive at about 2:30 and my goal was to make the roundtrip in four hours. On the way back I took Highway 18 instead of Cedar Grove Rd SE, which wasn't that scenic and smelled of landfill.

I left our house at 4:00 pm, with a full standard mode charge at 194 ideal miles. I reset the trip meter so I could easily track mileage and energy used. I left later than I had hoped, and I paid for it by being stuck in traffic pretty much the entire way from Issaquah to Enumclaw. That didn't help with my four-hour goal.

Give or take a few stunning views of Rainier near Black Diamond, the drive didn't get fun until I left Enumclaw (and the traffic) and got onto SR 410, a two-lane road through forest. I was pushing to make up lost time, but mindful of the risk of deer crossing the road, so I kept the speedometer at or a little above the speed limit. I didn't see much traffic and only passed one vehicle, a van going well below the speed limit.

I neglected to record state when I entered the park to begin the ascent up the mountain, but I recall the battery being around 90 ideal miles and the trip odometer would have been around 70. At about 4 miles from Sunrise, the trip and battery state crossed at 79 miles driven and 79 ideal miles left in the battery pack. If I were on level ground, I would have been considering bailing at that point, but I knew I had used extra energy climbing that I would get back on the descent. Also, I was still driving in standard mode, so I could switch into range mode to get another 25 miles of range.

The best part of the drive was the winding ascent up the mountain, wonderful conditions for the Roadster, although the road was pretty uneven in spots. I was having fun but not being crazy about it. Two thirds of the way up the mountain, I came up behind another car and resigned myself to taking the rest of the drive at his pace, which would have been fine. However, as soon as I came up behind him, he immediately pulled over to let me pass. I don't know whether he was scared of the red sports car, or just really nice. I waved in appreciation as I passed.

I arrived at Sunrise at 6:08 pm, just a few minutes later than my goal time. I let the car sit for a few minutes while I tracked down a restroom and snapped a quick photo. Ready for the return drive, the trip meter said I had driven 83.7 miles and used 28.01 kWh. The touchscreen altimeter said 6300 ft, temperature at 60 F, with the SOC at 47% and 69 ideal miles (standard mode).

For the descent, I got regen nearly the entire way. I stopped twice on the way down, once at the viewpoint just below Sunrise where I got my cell phone signal back and called to update Cathy on my progress, and at the bottom to record data. At the park exit, 14.0 miles from Sunrise, the battery state was up to 71 ideal miles, a net gain of two ideal miles from the reading at the top.

I was treated to a beautiful sunset with a thin crescent moon just above the horizon as I was finishing up the drive on SR 410 approaching Enumclaw.

I had a TomTom GPS navigation device programmed for the route home, mostly to show me remaining miles and ETA. When I left the summit at 6:20 or so, it was predicting I would get home just before 9:00, which was obviously wrong since I made the trip there in just over two hours. After exiting the park, the ideal miles tracked the remaining miles pretty closely, showing a buffer of about 10 miles the entire way, while the ETA dropped steadily.

I got home at 8:20, missing my four-hour goal by about the length of my stops. The trip meter read 168.8 miles and 41.76 kWh. Our house is about 100 ft elevation, so the trip involved climbing then descending 6,200 feet. The battery pack was showing a temperature reading of four (the highest of the blue ticks), PEM and motor at 3. After sitting for 20 minutes to stabilize, the state of charge read about 5% of the battery left, 9 ideal miles.

Charging back up to full (standard mode) from 240V/40A took 5:20 and put 44 kWh back into the battery pack. The meter on the wall indicated it pulled 50.0 kWh hours, or 296 Wh/mi from wall to wheel, about 12% below my average of 336 Wh/mi.

If Watt-hours per mile doesn't mean anything to you, at 9 cents per kWh for "green power" from Puget Sound Energy, it cost me about $4.50 to drive 168.8 miles, or about 37.5 miles per dollar of green electricity.

My take-away from the drive:

The roundtrip can be done on a single standard mode charge, but if you have a passenger or are farther away than Sammamish, I'd recommend a range mode charge.
If you do it on a weekday, start early enough to avoid the evening rush hour.
Take a credit card: it costs $15 to get into the park via the automated kiosk. Cash might also work.
Driving through the woods at sunset on a warm day leaves the front of your car covered with a thick layer of bugs.

Drag Racing a 2008 Tesla Roadster

Sun, 16 Aug 2009 11:49:39 -0800

I joined four other Seattle-area Tesla owners in driving down to Portland for the NEDRA Wayland Invitational IV electric vehicle drag racing event at Portland International Raceways on July 24th and 25th. My friend Richard wasn't due to receive his 2010 Roadster for another week or two, so he and I shared the driving and the racing in my car.

None of us had any previous drag racing experience, we were just doing it to promote electric vehicles by showing a bunch of people that EVs can be as fun and powerful as gas-burners without sending a bunch of our our dollars overseas or dumping CO2 into the atmosphere.

Over the two days, thanks to Northwest Handling Systems, John Wayland, James Morrison, and several others behind the scenes, who arranged charging both on and off the track, I was able to post the best time in a 2008 Roadster: a 12.982 second 1/4 mile ET at 103.48 mph. The best Roadster time was set by Scotty Pollacheck (the professional driver/rider of the famous Killacycle) in James Morrison's freshly-delivered 2010 Roadster sport: 12.643 second 1/4 mile ET at 102.89 mph.

At the Wayland Invitational, I got to race head-to-head against other 2008 Roadsters using the same driving technique and as well as controlling other parameters. Having Richard racing in my car allowed me to compare how weight changed times with other parameters held constant. Also got to race against the famous White Zombie. We had two nights there, one with charging at the track and one without. My YouTube channel has some videos from that weekend.

Two weeks later, the same group of owners spent another evening at Pacific Raceways in Kent, WA this time with Richard driving his shiny new 2010 Roadster. I was able to do some more experiments there.

Based on what I've seen so far, it breaks down like this:

13.40 seconds: 2008 Roadster, medium weight driver with a cool battery pack, single foot start, traction control on, racing in warm weather at sea level.

0.32 seconds - having a warm battery pack from a recent 240V/40A charge
0.10 seconds - traction control off
0.07 seconds - lose 20 to 30 lbs of driver weight
0.07 seconds - two-footed start (indirect estimate)

I didn't compare single foot launch and two-foot launch with all other parameters controlled. From otherwise similar runs in Portland and Kent, I saw a difference of about 0.07 seconds, but that was different tracks, different charge profiles and different ambient temperatures. The other delta were pretty well controlled.

One owner in Portland increased tire pressure to 40 psi all around trying to shave off a few hundredths to break into the high 12's and didn't get any benefit.

There's also some variation from car to car depending on how well the motor was wound, etc. While there was about 0.07 seconds difference between Richard and me in my car (presumably due to weight), there was a much smaller difference between Scott in his car and me in mine (0.04 seconds) even though I would guess the weight difference to be similar.

I didn't sense the stock tires spinning even with a two-foot launch and TC off, so I don't see how sticky tires would help on a 2008 Roadster. I have confirmation from Tesla to not expect the 2008 Roadster to spin the stock tires with TC off when on dry pavement and driving in a straight line. (That said, I am not recommending turning off TC in any other circumstance.)

I didn't get a chance to try all of the optimizations on the same run. It was only on the second day of the Wayland Invitational that I had a chance to charge up at the track and that was before I learned about the two-foot launch technique in detail, and also before I had the nerve to turn off traction control. So, I don't know what happens when you stack up all of the techniques together.

According to my data, getting a stock 2008 Roadster under 12.8 is going to take a trick I don't know about. Perhaps a driver under 100 lbs, or driving at higher altitude could do it. It might also help to fold back the side mirrors to reduce drag. It will be interesting to see what happens at the NEDRA nationals in Denver in September.

DEFCON 17 Report

Tue, 04 Aug 2009 11:48:09 -0800

DEFCON is an annual computer security conference, the inexpensive and unruly counterpart to the more expensive corporate Black Hat security conference. From computer security briefings to the toxic barbeque to lock picking contests to a 52-hour competition to turn the electric conference badge into something more by any available means, DEFCON has something for everyone.

My focus is generally attending the briefings on computer security, privacy and civil rights issues, but even that consists of five parallel tracks of concurrent talks, so I only get to see a fraction of what's being presented.

That said, here's my summary of what I learned this year.

Picking the Lock on Your Browser

I trust everyone knows that when you're entering sensitive personal information, like bank account and credit card numbers, into a web page you need to look for the little lock icon so that you know you aren't revealing your info to some malicious criminal. Technically speaking, the lock (along with the https:// in the address bar) guarantees that you are sending that info to the web site you intend (not some malicious forgery) and that the info is being sent in an encrypted form so that even if a criminal is recording all of the data as it is transmitted across the Internet, your private information can't be read.

For the lock to be effective, you need to make sure you entered the correct address into your browser. Getting you to enter an incorrect address is the basis of what is called "phishing." One example of phishing is sending fake email messages that look like they came from your bank, or eBay, or Amazon, etc., which encourage you to follow a link in that email. The link might look like a link to the proper institution, but the actual address is to another site. For example, you might be sent to http://ebay.criminalscammer.com/ which has no association with ebay.com and will instead steal your eBay credentials if you type them into their bogus site. The fake link can be very insidious where it uses some wacky foreign alphabet character that makes the link look like the right web site, something like bankøfamerica.com. You might notice the slash through the "o", but there are other character substitutions where there is no visible difference.

This brings us to the first two rules of Internet safety:

Rule 1: Don't trust a link that you get in email, no matter who it says it's from. Especially don't trust it if it takes you to a bank or commerce web site. Even links to non-commerce sites can be malicious, since there are flaws in browsers that allow a malicious web site to take over your computer, but that's a whole different topic. So, if your best friend in the whole world emails you a link to the funniest photo ever, and you just have to see it, be skeptical and consider verifying the source of the link before clicking it.

Rule 2: Whenever you are about to type anything into a web page that you wouldn't want posted on the bulletin board at the local prison, make sure the link starts with "https://" and that your browser is showing you the lock icon.

That's where we were until early 2008. As long as you always typed in your web addresses, or used bookmarks you created from web addresses you typed in, and you looked for the https:// and the little lock, you were safe.

Then last year, Dan Kaminsky found a problem, but first I have to explain another vulnerability.

There's a step in the web communication process that can be subverted. When you type https://www.yourbank.com/ into your address bar, your browser has to do something like looking up a phone number. Computers on the Internet aren't addressed by name, but instead by a number called an IP address. It's like when you place a phone call, you don't type in someone's name, you enter their phone number. There are special servers on the Internet, called DNS servers, that perform that lookup. So, when you type https://www.yourbank.com/ into the address bar, your computer connects to a DNS server and asks for the correct IP address. That process can be subverted. It's been known for a long time that it's easy to do this locally. So, if you're using the WiFi connection at your local coffee shop, some criminal might also be sipping coffee there and sending your computer fake DNS responses that will send you to their evil server instead of your bank's server.

Rule 3: Don't trust web pages when you're surfing from a public access point. This includes free WiFi at coffee shops and libraries, and also wired Internet connections at hotels, Internet cafes, etc.

That used to be a good rule, until Dan Kaminsky pointed out a problem in the DNS system that has been there for years. There was a flaw in the programming used by DNS servers that made it possible for the bad guys to attack the server and trick it into sending our false information. So, even if you typed in https://www.yourbank.com/, the real DNS server might send you a bogus response that would send your browser to a criminal web server. This is a very bad problem as nearly all of the millions of DNS servers out there were vulnerable. Dan worked closely with the folks who control the majority of the DNS servers to get the flaw fixed on as many servers as possible before announcing the problem to the world.

The careful reader might be thinking that even if someone fakes your DNS responses and sends you to the wrong site when you're trying to do your banking, the https:// and the little lock means that you are connected to the real bank site and your information is encrypted so it can't be read even if it's intercepted. That was true until...

Getting Valid Certificates for Fake Sites

This year at DEFCON, Dan Kaminsky announced another flaw in a major system behind the safe operation of the Internet: it's possible for the bad guys to trick browsers into thinking they have valid certificates for sites they don't own. Certificates are the mathemagical basis of how your browser's little lock icon determines that it's safe to enter and send your private information securely to the party you intend and no one else. The certificate does two things: it proves to your browser that the site it's talking to is the real site for the address in your address bar (which is why it's critical that you have the correct address in your address bar) and it gives your browser the means to establish a secure communication channel to that server which can't be read by anyone else even if they intercept all of your transmitted data. It is widely believed that this security cannot be broken even with a lifetime of effort by an army of supercomputers. And that's still the case, except: the bad guys can get real certificates that allow them to impersonate secure sites.

The trick is somewhat technical, but it is fixable. Hopefully, this flaw will be taken as seriously as the DNS issue was and the several contributing flaws will all get fixed soon. If you're not interested in the technical details of the flaw, you can skip the next paragraph.

When you apply for a certificate from one of the many certificate authorities, you submit a document that states what domain name you want secured. There are multiple formats for encoding this string, including preceding length byte and zero-byte terminated. If you combine both, evil ensues. For example, you can submit a form using the length-byte format for the domain [37]www.yourbank.com[0].criminalscammer.com where [37] represents the length byte covering the entire string and [0] represents a zero byte in the middle of the string. Some certificate authorities will parse this string, pay attention of the length byte, but recognize that the zero-byte isn't a valid character (the digit '0' is not represented by a zero-value byte in order to avoid confusion when using zero-byte terminated strings, see info on ASCII encoding) and parse the string as www.yourbank.com\x00.criminalscammer.com. Their computer decides this is a perfectly reasonable request and contacts the owner of the criminalscammer.com domain to make sure the request came from them. The criminal scammer validates the request and the certificate is granted. The problem comes when a browser gets a bogus DNS reply for www.yourbank.com which directs it to contact the evil server with the wacky certificate. When the browser encounters the zero-byte, it may interpret the wacky domain name differently than the certificate authority and treat that zero-byte as the end of the string and decide the certificate is for www.yourbank.com.

Once this is set up, the victim submits banking info to the evil server and now the bad guys can log into the user's bank account. That's a bad thing.

The good news is that for this to be a problem two things have to occur. First, the user has to get directed to a fake site through a bogus DNS reply, and second the browser has to have the flaw that allows it to see the phony certificate as valid for the legitimate site. Which brings us to:

Rule 4: There is no rule four, follow rules 1 through 3 to avoid getting sent to a counterfeit web site.

We hope that certificate authorities will stop granting these zero-byte certificate requests and browser vendors will fix their code that interprets these fraudulent certificates.

Colleges Throw Out Students' Internet Privacy, Expose to Fraud

Endgrain, an observant student at the University of Southern Maine noticed something odd when he entered a chat room after logging into the university's network: people in the chat room started addressing him by his full name. He did some sleuthing and found out how his university was broadcasting his full name to everyone on the Internet.

When a student at USM logs into the network for the first time, they have to enter their username and password. The network then remembers that machine (by its MAC address) and thereafter lets the user onto the network without entering credentials. It also assigns that student an fully Internet accessible IP address, and maps that IP address to a domain name that includes the student's first and last name. There are a number of problems with this scheme.

First, because the IP address is publically available on the Internet, with no intervening router or firewall, the student computers are open to direct outside attack from anywhere on the Internet.

Second, because the IP address has a full DNS name revealing the student's name, the student is fully exposed to all sorts of privacy attacks. Every web site they visit logs those visits, and hence logs the student's name. Likewise, Google searches are logged and thus a student's search history is exposed to the world. Many other Internet activities expose students to a loss of privacy.

USM isn't the only school doing this to students, at least the practice of assigning DNS names that include each student's full name. According to research done by Endgrain and Dan Kaminsky, some 60 universities are doing this.

Presumably, this destruction of student privacy is done to streamline RIAA lawsuits against students pirating music. With the DNS clearly revealing a student's name, university, and even approximate location on campus, the RIAA can serve up lawsuits without having to go through the bother of getting a court order to find out who is behind an IP address identified as illegally sharing music.

The worst part of this whole thing, at least as USM has implemented it, is that it actually hurts the ability of the RIAA to identify who's behind an IP address. Anyone on the university network can watch traffic and determine which MAC addresses belong to which students. It's then trivial for a malicious student to spoof another student's MAC address then do bad things masked by the DNS name pointing to an innocent student all without ever learning that student's network password. Because of this flaw in how USM allows unsecured logins by MAC address, any student who gets sued by the RIAA has an easy defense: it's wasn't me, someone must have spoofed my MAC address. Guilty students get an easy defense, and innocent students are left to defend themselves in court because of a flawed system.

Everyone loses here. Students lose their anonymity on the Internet and can be identified by anyone, with no need for having a good reason to identify a user or obtain a warrant or court order. The RIAA, and other intellectual property owners, can't actually use the DNS names to identify students since the system is so easy to subvert. Universities look like spineless dorks for outing their students and exposing them to computer attacks.

Students who go to universities that are doing this to their student body should be raising the alarm and forcing a change in policy. We don't want our universities to be teaching students that they have to abandon their first amendment rights for the illusion of corporate convenience.

Elon Musk Explains the Roadster Price Increase

Thu, 22 Jan 2009 08:34:21 -0800

The following email was sent to Tesla Motors customers on Tuesday, January 20th.

From: Elon Musk, Tesla Motors
To: Tesla Roadster Customers
Date: Tue, 20 Jan 2009 12:45 pm PST
Subject: The Importance of Options

A much fuller account of the history of Tesla is worth telling at some point, but for now I will just talk about the essentials of why we needed to raise prices on options. Fundamentally, it boils down to taking the tough steps that are difficult but necessary for Tesla to be a healthy company and not fall prey to the recession.

When the initial base price, for cars after the Signature 100 series, of $92k was approved by the board a few years ago, it was based on an estimated vehicle cost of roughly $65k provided by management at the time. This turned out to be wrong by a very large margin.

An audit by one of the Series D investors in the summer of 2007 found that the true cost was closer to $140k, which was obviously an extremely alarming discovery and ultimately led to a near complete change in the makeup of the senior management team. Over the past 18 months, observers will note that Tesla has transformed from having a senior team with very little automotive experience to one with deep automotive bench strength. We now have executives with world class track records running everything from design to engineering to production to finance.

To bring the cost of the car down, we have reengineered the entire drivetrain, which is now at version 1.5 and will be at version 2 by June. The body supplier was also switched out from a little company that was charging us nutty money and had a max production of three per week to Sotira, who supplies high paint quality body panels to Lotus, Aston Martin and others. In the process, we had to pay several million dollars for a whole new set of body tooling, as the old tooling had been made incorrectly. The old HVAC system was unreliable and cost almost as much as a new compact car, so also had to be replaced. The wiring harness, seats, navigation system and instrument panel also had to be modified or replaced.

After reengineering and retooling virtually the entire Roadster and completely restructuring our supply chain, we are now finally coming to the point where the variable cost of the car (to be clear, this excludes fixed cost allocation) is between $90k to $100k. With a lot of additional effort by the Tesla team and the help of our suppliers, we should be at or below $80k by this summer. There is some variability here due to exchange rate shifts. Although we gain an automatic currency hedge by selling in both Europe and the US, we are still vulnerable to the Yen, which is very strong right now.

Obviously, this still creates a serious problem for Tesla in the first half of 2009, given the $92k to $98k price of most cars delivered over this time period. The board and I did not want to do a retroactive increase of the base vehicle price, as that would create an unavoidable hardship for customers. Instead, apart from a $1k destination charge increase to match our true cost of logistics, we only raised the price of the optional elements and provided new options and a new model (Roadster Sport) to help improve the average margin per car.

The plan as currently projected, and which I believe is now realistic, shows a high likelihood of reaching profitability on the Roadster business this summer. By that time, we will be delivering cars that have a base price of $109k plus about $20k or so of options (having worked our way through the $92k to $98k early buyers) at a rate of 30 per week. We are fortunately in the position, rare among carmakers, of not having to worry too much about meeting 2009 sales targets, as we are already sold out through October and have barely touched the European market.

My paramount duty is to ensure that we get from here to there without needing to raise more money in this capital scarce environment, even if things don't go as well as expected. I firmly believe that the plan above will achieve that goal and that it strikes a reasonable compromise between being fair to early customers and ensuring the viability of Tesla, which is obviously in the best interests of all customers. It's also important to note that the price increases will affect 400 customers, all of whom will take delivery after Jan. 1 and receive a $7,500 federal tax credit. We made the pricing changes to ensure the viability of Tesla in the long term, regardless of government incentives, but we hope the credit will offset the increase for most customers.

There is one additional point that relates to the government loans that Tesla is seeking for the Model S program, a much more affordable sedan that we are trying to bring to market as soon as possible. A key requirement is that any company applying be able to show that it is viable without the loans. If we allow ourselves to lose money on the cars we are shipping today, we place those loans at risk. Mass market electric cars have been my goal from the beginning of Tesla. I don't want and I don't think the vast majority of Tesla customers want us to do anything to jeopardize that objective.

Elon Musk
CEO & Product Architect

The New Tesla Prices

Sat, 17 Jan 2009 09:19:42 -0800

Here is the new pricing table updated with the information in the letter sent to Tesla Roadster owners on January 16th. This is an unofficial compilation for comparison purposes, based on my understanding and interpretation of the old and new packages, options and prices. Please post any corrections in the comments.

The email describing the new options and pricing did not detail the cut-off between the old pricing and new pricing, but I believe the new pricing applies to all 2008 model year Roadsters which had not already entered production. I will update as details become available.

Note that there are significant changes from the options communicated to owners nearing production earlier in the week.

The following options were previously available and are now available at adjusted prices and in different bundles:

Original ($)

Current ($)

SolarPlus Windshield

(included)

400

High Power Connector

(included)

3,000

Forged Alloy Tesla Wheels

(included)

2,300

Painted Hardtop

3,200

Metallic Paint

500

1,000

Premium Paint

1,000

2,000

Paint Armor

approx 1,400

1,495

Premium Interior

1,800

Floor Mats

125

150

Mobile Connector (120V/15A & 240V/40A)

350

N/A

Mobile Connector (120V/15A)

N/A

(included)

Mobile Connector (120V/15A) Additional

N/A

600

Mobile Connector (240V/30A)

N/A

1,500

Upgraded Stereo Head Unit
with Navigation System

1,200

N/A

Bluetooth

100

N/A

Sat Radio

400

N/A

Premium Speakers

800

N/A

Homelink door opener

(included)

N/A

Electronics Group
(includes above 5 items)

N/A

3,000

Destination Charge

950

1,950

The apparent change in the 240V mobile charger from 40A to 30A may be to satisfy regulatory requirements. I will update this when I find out more from Tesla.

These are new options not previously available:

	Price ($)
Executive Leather Interior	6,000
Premium Carbon Fiber and Leather Interior	9,000
Clear Carbon Fiber Hardtop	5,000
Clear Carbon Fiber Accent Group	9,000
Performance Tires	850
Custom Tuned Adjustable Suspension	4,000
Battery Replacement	12,000
Extended Warranty (2yr/24,000 miles, excludes battery)	5,000

At this time, we don't know what the performance tires are or how they compare to the current and previous standard tires. I will update when we learn more.

Price Increase

The price increase for owners who had previously locked in their options depends on which options were chosen and which previously standard options the owner is willing to give up. Here are some examples:

Increase

Scenario

$ 1,000

New base model, losing alloy wheels and SolarPlus windshield, and replacing HPC with 120V/15A mobile connector.

$ 6,700

The previous base model configuration with no options added, which includes the HPC, the SolarPlus windshield and the silver forged alloy Tesla wheels; also gets 120V/15A mobile connector.

$ 9,350

Fully loaded model from previously available options, mobile connector reduced from 240V/40A to 240V/30A.

Revision History

Jan 17 2009 13:44 PST: revised table of examples to include original base model.
Jan 17 2009 23:32 PST: confirmed that Homelink transmitter was standard equipment.

Tesla Increases Prices on Locked-In Orders

Thu, 15 Jan 2009 09:29:46 -0800

Update: Tesla Motors announced the new options and pricing to all owners on Friday, January 16th. I've posted an updated analysis.

Tesla Motors is in the process of rolling out price increases to their customers who have pre-ordered a 2008 model year Roadster which has not yet entered production. Customers whose cars are about to enter production, after a two-year wait and a fourteen-month delay, are right now getting phone calls in which they are told they have to accept this price increase and re-select options before their car can go into production. This price increase applies to all 2008 Roadster orders starting with VIN 210.

These 2008 model year customers were given a base price of $92,000 and required to make a substantial deposit at a small start-up company with no experience in producing cars. Those early deposits of $30,000 to $50,000 were used along with investment capital to fund the development and early production of the Roadster. Around the time that Tesla delivered their first production car in February of 2008, they opened orders for 2009 model year cars at an increased base price of $109,000 to reflect both increases in their cost projections and also the then-proven ability of the company to produce cars.

Customers whose cars are going into production this month were required to lock in their option selections in September. All customers with orders for 2008 model year orders, some 600 cars, were required to lock in their selections by November of last year. Tesla Motors is unlocking those selections, raising the prices, and requiring owners to reselect their options with the higher prices.

This is coming as a big surprise to owners being informed of this given that they locked in their options and price months ago. A casual reading of our contract sure makes it sound like once we locked in our choices we were committed to buying the Roadster with those options, and Tesla Motors was committed to delivering that package for the price we agreed to.

Here is the table of original and current options and prices as provided by Tesla Motors on January 14th, 2009.

	Original Price	Current Price
Base Vehicle	$92,000	$92,000
SolarPlus Windshield	(included)	$400
High Power Connector	(included)	$3,000
Mobile Connector	$350	(included)*
Hardtop	$3,200	$3,200
Metallic Paint	$500	$1,000
Premium Paint	$1,000	$2,000
Premium Interior	$1,800	$1,800
Floor Mats	$125	$150
Navigation System	$1,200	N/A (see stereo bundle)
Bluetooth	$100	N/A (see stereo bundle)
Sat Radio	$400	N/A (see stereo bundle)
Premium Speakers	$800	N/A (see stereo bundle)
Stereo Bundle	N/A	$3,000
Destination Charge	$950	$1,950
New Options
Performance Tires	N/A	$1,150

The most obvious price increases are from the unbundling of the high power connector (HPC) and a $1,000 increase in the destination charge. The HPC connects the Roadster to home power for rapid charging. Previously, the HPC was included in the price of the Roadster for early orders. (Tesla had previously unbundled the HPC for 2009 model year orders.)

A second big change is the removal of à la carte audio upgrades. Previously, owners could choose to separately upgrade the speaker system and head unit (including a navigation system). With the upgraded head unit, owners could choose to add support for Sirius satellite radio and/or Bluetooth mobile phone integration. Now all of these items are available only as a single bundle for $3,000, which is $500 more than the total system cost originally. The option of spending just $800 for the built-in premium speaker system is no longer available, a disappointment to owners who wanted the factory speaker look with an aftermarket head unit.

There's also a subtle change in the mobile connector. Previously, owners were able to order a mobile connector for charging away from home. The promised mobile connector was to be compatible with both 120-volt and 240-volt connections using a variety of outlet adapters. Tesla later discovered regulatory hurdles to selling a 240-volt connector, so now owners have only a 120V/15A connector that takes about 37 hours to charge a fully depleted battery pack. Said another way, the mobile connector charges at a rate of about 6 miles of added range per hour of charging. Tesla is now including that 120V low-power mobile connector at no charge, with no timeframe or cost estimate for the 240V/40A mobile connector.

According to Doreen Allen, Tesla Motor's reasoning for the price increases is that they are working hard to get to being profitable on each Roadster delivered, and that the federal tax credit of $7,500 which became effective on January 1, 2009, means that the net effective price of the Roadster decreased at the beginning of this year. Additionally, the à la carte audio options were creating too much complexity in production and had to be consolidated to be sustainable.

This owner finds it particularly galling that he and his wife got the message from Tesla that our car is being held from starting production until we agree to these sudden, retroactive price increases on the same day that Tesla Motors published a blog Tax Incentives: Why the Roadster costs less than its sticker price.

On a personal note, we complained a lot, but in the end picked a set of options and agreed to pay the price increase because we want Tesla to be successful and we want our car as soon as possible. It didn't seem worth it to spend a week complaining and arguing about it, not when our car was ready to go into production.

Lies, Damned Lies, and Plug-in Hybrids

Fri, 14 Nov 2008 12:59:18 -0800

Gas/Electric Hybrid Vehicles

About ten years ago, the Toyota Prius and Honda Insight entered the US car market and have grown to change the way we think about automobiles, the environment, and energy efficiency. Starting slowly at first, sales of the Prius took off and now they are one of the most popular models sold in the US.

These hybrids are simple to understand: they run on gasoline just like every other car on the road, but they have a battery pack and electric motor that makes them more efficient: they get very good gas mileage.

But it's an odd design to meld two drivetrains into a single vehicle. Why is it more efficient to make a gasoline engine push around an electric motor and battery pack, and also make an electric drive push around the gas engine and fuel tank? It's not clear to me that it is that efficient. If you look at the top fuel efficient 2009 vehicles according to the EPA, you'll see that the top vehicles are hybrids, but their advantage is mostly in city driving. The diesel Jetta is just 10% less efficient than the Prius on the highway. In Europe, there are even more efficient diesel vehicles.

Hybrids work well for city driving because they use regenerative braking to capture some of the energy that is normally just dumped into wearing out your brakes when you slow down for a stop light. Even though only a portion of that wasted energy gets stored in the battery pack, it's enough of an improvement to make the double-drivetrain vehicle more efficient.

Hybrids are able to offset some of the weight of the electric drive by using a smaller gas engine. The electric drive can help push the vehicle up a hill, and get some of that charge back on the down slope.

Gasoline engines are only about 25% to 30% efficient. That is, only about 25% of the energy contained in a gallon of gas makes it to the wheels to propel the car. The rest of that energy is wasted as heat and mechanical inefficiency. A good part of that gets wasted in the transmission because a gas engine only produces high power/torque in a narrow band of RPMs, so multiple gears are required for good acceleration at a wide range of speeds.

An electric drivetrain can be over 80% efficient. There's no heat wasted in exhaust and no reciprocating pistons. Also, an electric motor can deliver high torque and power over a very broad RPM range, so there's no need for a transmission and thus no mechanical losses there. That's how adding the weight of a second drivetrain that is just fed with a fraction of the kinetic energy normally wasted by braking can improve the efficiency of a gas engine in city driving.

Plug-in Hybrid Electric Vehicles

If that little bit of saved energy can be used to create a more efficient vehicle, wouldn't it be even better to use some grid electricity to further increase vehicle efficiency? Power plants generate electricity more efficiently and cheaply than using a gas engine to generate electricity indirectly through regenerative braking. So, maybe we should further augment a hybrid's power with grid electricity.

That's a promising idea, and is the basis of plug-in hybrid electric vehicles, or PHEVs. There are actually two PHEVs that are generating a lot of buzz now: the Hymotion Prius upgrade and the Chevy Volt.

Hymotion created an after-market upgrade that turns a standard Toyota Prius into a PHEV by giving it an additional battery pack that can be charged from an ordinary outlet.

The Chevy Volt has an even more innovative design: it has a pure electric drive, only the electric motor is connected directly to the drivetrain. It also has a small, gasoline-powered generator that is only used to recharge the battery pack. Because the gas engine is only used as a generator, it can run at its most efficient power level and avoid the gross inefficiencies associated with a car's engine that has to run a wide variety of RPMs and load levels outside its most efficient power range.

Lying about Efficiency

The PHEV is a surprisingly more complicated solution in part because we have no way to talk about the efficiency of this type of vehicle. We're used to evaluating vehicle efficiency by looking at miles per gallon. That works great with a hybrid, because the only energy input is gasoline, but what about a PHEV? The easy thing is to just quote an MPG number and move on, but that doesn't tell you anything.

Consider a different case. Suppose I invent a new kind of hybrid vehicle: gas and propane. It has two engines, a conventional gasoline engine and a propane engine. Together, they power the vehicle's drivetrain. When I take my new model into the EPA to get its fuel efficiency rating, I fill up both tanks. The EPA drives the vehicle on their standard course and find that the car traveled 200 miles and used two gallons of gas, so it gets an EPA rating of 100 mpg.

But what about the propane? How much propane did the car use up? How much does that propane cost? How does the use of propane and gas change with different driving conditions? We already have city and highway numbers, but maybe this new hybrid is even more complicated. How does the hybrid bit work, does it burn propane until it runs out, then switches to gasoline, or does it burn both equally over the entire range? How are consumers going to evaluate what it will cost them to drive this vehicle on their daily commute. How will environmentally-minded consumers evaluate its overall energy efficiency and carbon footprint?

Obviously, was can't just quote an MPG number for a hybrid vehicle that takes in two different fuel/energy sources. That would be misleading. In fact, unless the MPG number works in all driving scenarios, it would be fraudulent.

The same issue applies with PHEVs. If we just get an MPG number, that tells us nothing useful unless we understand how the trade-off between gas and electricity works under our individual typical driving conditions.

The Volt and the EPA

Consumers will want some sort of fuel efficiency number and consumers understand MPG, so GM talked to the EPA and argued that the EPA should use a testing regimen that will give the Chevy Volt a rating of over 100 MPG. The problem is that if the EPA allows the Volt to use the battery pack without accounting for the extra energy input, it gets over 100 MPG, but only about 48 MPG if they don't allow it to deplete the battery pack. The truth perhaps lies between these two numbers and depends on an individual's driving profile.

It's really important that the conversation doesn't stop with this one deceptive measure of fuel economy. The Chevy Volt can go 40 miles on just electricity. That's great if my daily commute is under 40 miles (and that's true for 78% of personal travel in the US according to a 2003 Department of Transportation study), but if I go over that, is it the same as driving a Prius? Unlike the Prius, the onboard engine isn't powerful enough to power the car, it can only add charge to the battery pack. If you just keep driving, eventually the battery pack will run out, and simply filling up the gas tank doesn't refill the source of power that drives the wheels. So, how far can you go? The answer is going to be complex since the gap between what the car pulls from the battery pack and what the generator puts in depends on the speed you're driving. That's not an issue with the Prius, but it's something potential Volt buyers need to understand.

The same issues apply to any PHEV that uses a small gas engine only as a battery-charging generator.

The Hidden Cost

Not only does MPG not tell us enough about how much gas the car uses, while also skipping over the cost of electricity,* it completely hides the cost of the huge compromise built into a PHEV.

The very best battery technology available today is called lithium-ion. This battery chemistry has the best balance of cost and energy density. For a given weight in batteries, lithium will allow you to store the most charge at a reasonable cost. And the cost isn't cheap, either. Lithium ion batteries are more expensive than lead-acid (like your regular car or boat battery) or the nickel metal hybrid batteries used in hybrids like the Prius.

None of these battery chemistries used in vehicles like to be overcharged or fully discharged. If you've ever left your lights on overnight and not only drained your battery, but also ruined it, you know what I'm talking about. With an electric vehicle, there's a computer that monitors battery charge state and keeps you from damaging the batteries, so you don't have to worry about it, but it does have performance implications that prospective buyers need to know about.

Consider a pure electric vehicle like the Tesla Roadster. It has a large pack of lithium ion batteries, big enough to support an EPA verified range of 244 miles (mixed city and highway). Since most commutes are far less than this, 78% under 40 miles and 92% under 70 miles, this means most driving in the Roadster will only need to use the middle of the charge range: it doesn't need to be fully charged nor fully discharged to handle daily driving. This is the best way to ensure maximum battery life. If a Tesla driver frequently uses the entire maximum range of the battery pack, the lifetime of the battery pack will be shortened. The Roadster is not your best choice as a road trip car. Fortunately, road trips represent a small fraction of travel in the US, so this isn't a problem, just something to think about when you're choosing between the Prius and the Roadster for that big road trip.

But what about a plug-in hybrid, like the Chevy Volt with a 40-mile electric range? Obviously, GM has to keep the battery weight down since the car is already packing two power plants. The Volt is designed and marketed as being pure electric for a 40-mile daily commute. If GM were to put in a battery pack that could just barely manage the forty miles, then drivers would put a full charge cycle on it every day. That would kill a lithium ion battery pack in about two years. Let's assume they want their product to last longer than that.

Since the car is designed to be gas-free for a 40-mile commute, that battery pack has to be capable of much more than just 40 miles while also bearing the burden of pushing around a gas engine, generator, fuel tank and exhaust system. So, GM decides what an appropriate charge capacity margin is, and puts in a battery pack that large.

Let's suppose they only want to use the middle 50% of the charge range, so the battery pack is only charged to 75% and only discharged down to 25% (which is about what Toyota uses in the Prius). Based on that assumption, if you drive a Volt on your 40-mile commute, you're going to use half a discharge cycle every day. You bought a battery pack that is capable of an 80-mile trip if you are willing to compromise battery life for an occasional long trip. In fact, if you could pull out all the extra weight of the gas generator, your battery pack could maybe handle a 100-mile trip. Instead, you only get the 40 miles, while still also hammering the battery pack pretty hard, and dealing with all the maintenance hassle of maintaining the gas engine.

Maybe 50% charge buffer isn't the choice that GM makes. If they pick a smaller charge buffer, the battery pack wears out sooner. If they pick a larger buffer, then they are just wasting more battery pack on a hobbled electric drive that could handle even longer occasional pure electric trips. Not matter how you slice it, trying to drive a daily commute with a small battery pack burdened by extra generator weight wastes the full electric potential of the vehicle.

Driving Pure Electric

Compare that to a pure electric vehicle with a 240-mile range. You can do your 40-mile commute with just one sixth of the battery pack's charge cycle, and you have a car that can go over a hundred miles with less impact on battery life than your daily commute in a Volt. Even a 200-mile trip is possible while leaving 20% of the charge range untouched. That's excellent battery life in a vehicle that never burns any gas and is capable of a good long drive, especially if you can get access to an outlet at your destination.

Right now there aren't many choices when it comes to driving pure electric, but that's changing. Just like when any new technology is introduced, initial models are expensive and produced in low volumes. Even the Model T was viewed as a rich man's toy when it came out. With higher production comes both better availability and lower prices. Although electric vehicles have been around longer than gas-powered vehicles, the production electric vehicle market is in its infancy, but is about to get far more interesting.

Today, you can buy a high-end, pure electric sports car with a top speed of 125 mph and an EPA-certified range of 244 miles: the Tesla Roadster, available in limited quantities for a mere $109,000. If they cost less, you probably still wouldn't be able to get one because demand would far outstrip the production rate of about 1200 per year.

But Telsa isn't in the business of solving a shortage of expensive sports cars. Their mission is to get lots of affordable electric cars on the road, the Roadster is just the start. In 2011, just months after GM is expected to start producing the Volt, Tesla Motors expects to start delivering their $60,000 Model S, a luxury sport sedan with a range of about 240 miles. By 2012 or so they expect to deliver their third model, a $30,000 all-electric economy sedan.

But Tesla Motors isn't the only one in the game. Lots of companies, both big auto makers and daring start-ups are promising electric vehicles in the near future.

Aptera expects to start producing their Typ-1e, an EV with a 120-mile range in late 2008, available initially in California for $27,000. BMW is working on an all-electric Mini-E version of the Mini Cooper, available for lease through a pilot program this year in California, New York and New Jersey. In 2009, Miles Electric Vehicles expects to begin delivery of their highway speed sedan, cleverly called the "Highway Speed Sedan," with a top speed of 80 mph and a range over 100 miles for about $40,000. Daimler has plans to introduce electric versions of both a Smart car and a Mercedes in 2010.

Brother, Can You Spare a Trillion Dollars?

Meanwhile the big Detroit automakers have resisted years of pressure to produce more efficient vehicles, instead betting their profitability on giant gas hogs. Who could imagine that either environmental or national security concerns could sour the American public on huge gas guzzlers? Combine that with the brutally obvious result of global oil production leveling off while demand has continued to grow, literally exponentially. Is it any wonder years of short-sighted profiteering have put the big American automakers on the edge of bankruptcy? All of their lobbying to prevent more stringent domestic fuel economy standards while also locking more efficient diesel fuel vehicles out of the US market has destroyed their competitiveness overseas, and now the American buyers aren't interested in their bloated product lines either.

Their solution is to have the US Government pour hundreds of billions of dollars into the ailing US auto industry to pay for their past mistakes, while they try to retool to build incrementally more efficient vehicles based on a compromised PHEV design, hiding behind inflated and misleading MPG numbers.

That's not how I want my tax dollars spent.

*The cost to drive a car on electricity is generally really cheap, due to the superior efficiency of an electric drive, even taking into account power plant efficiency and transmission loses. But, the cost does depend on where you live. Also, the emissions associated with the energy used in an electric vehicle vary widely depending on how electricity is generated in your area.

The good news is that we are already motivated to green up our electrical generation and EVs benefit from that without changing the car at all, while their gas-powered peers get dirtier with age. Oh, and gasoline prices can only go up, give or take short term fluctuations: global production is flattening out while worldwide demand is increasing.

Tesla Motors - It's not just the economy, stupid!

Fri, 17 Oct 2008 09:29:31 -0800

Tesla Motors Announces Some News

On Wednesday, Tesla Motors Chairman Elon Musk announced some changes at the company. In a nutshell, they are going to:

Work to be cash-flow positive within six to nine months.
Ramp up the delivery rate for pre-sold Roadsters.
Build revenue from powertrain sales to other car companies.
Musk will replace Ze'ev Drori as CEO.
Drori will remain as vice-chairman of the board.
Scale back Model S work until their assembly site passes the environmental review.
Delay the production target for the Model S by six months.
Finance Model S production primarily with a low-interest DOE loan.
Implement a modest reduction in near-term headcount.
Survive the economic turmoil on Musk's dime for as long as it takes.

The media and blogosphere as been laser-focused on writing copycat stories on how the current economic problems have led Tesla to layoffs and the Model S delay. That generates eye-catching headlines, but it misses the real story.

Building a New Car Company

In February of 2007, Tesla announced their assembly plant would be in New Mexico. After over a year of silence on that, they announced a new plan in September: assembly plant in California. Clearly things aren't going as smoothly as Tesla had hoped.

Of course the Model S got delayed. They were running on a very tight schedule to deliver the Model S in late 2010. To get to that point, there's an incredible amount of work for them to do. Apparently they have made good progress designing the sedan, both inside and outside, but that's just the beginning. They also have to design and build a production facility and the assembly line tools and process, and create supplier relationships that will be 100% reliable. There's a lot of that work that depends on knowing when and where they are going to build their assembly facility. If and until they get the environmental approval for the San Jose site, they don't know either.

Also tied to the environmental approval is the DOE loan. If they wait for the loan to provide the majority of funding needed to develop the Model S, the Tesla investors can avoid giving up equity in another round of financing, e.g. an IPO. Right now, raising money from investors is more expensive, which further increases the appeal of the DOE loan. So of course they need to delay spending money unnecessarily until they can get the DOE funds.

Thus, cost cutting and modest layoffs. Now that they expect to have their headquarters located at their production facility, they want to consolidate operations. Combine that with Roadster design work being finished in Hethel, and some general belt-tightening and you have some layoffs. That's bad news for the Tesla people who will lose their jobs. I've met a number of Tesla employees and I've been universally impressed. They are a bright, enthusiastic bunch doing amazing and important work. I hate to think of people of that caliber losing their jobs. I hope they are able to quickly apply their talents to new jobs. It's bad news for those people, but it's not bad news for Tesla. It's just a matter of Tesla staying lean until they know when and where their Model S production facility will be built and can get working 100% on that huge effort.

The Real Risk

Here's the scariest part of Musk's announcement:

If all goes reasonably well, we will receive [the environmental] approval in Q2 next year.

Have you ever heard of an environmental approval going smoothly? If something kills Tesla Motors, it's not going to be the Wall Street fiasco, it's going to be some wet patch of dirt or an endangered species we've probably never even heard of. It's ironic that a company trying to develop technology to help save the global environment from man-made disaster is at risk of failure because of one of the literally millions of species that are threatened by the problem that Tesla would like to help solve.

But the media is having lots of fun writing about the subprime loan mess, reckless unregulated banking, and the resulting panicked federal intervention spending spree, so that's what they are writing about.

The Good News: Profits

There's even another thread to this story that has been completely missed:

Our powertrain business is profitable today and is also growing rapidly.

What is that all about? We've heard rumors that Tesla is working on an electric powertrain for another auto maker, but nothing has been confirmed. Now Musk tells us that not only are they doing it, but that it's already profitable. That's real news! That could be the single most important thing that Tesla has announced all year. It could be the beginning of a business model that puts Tesla's technology into vehicles in quantities that will show the world that the Roadster was just a successful gesture to get people thinking about electric vehicle technology.

It could well be the direct path to achieve Tesla's goal to reduce our global dependence on burning petroleum which is damaging our global climate, funding horrible governments around the world, and betting the entire free world economy on the whims of those undemocratic governments.

But how is the media going to work that into a story about today's immediate financial crisis? Especially if we have to ask questions and do research instead of just writing the same story everyone else is writing; that's just too hard.