Results matching “Tesla Motors”

For owners who may be new or unfamiliar with the Tesla Roadster, I'll run through the basic information needed to preserve this rare and special vehicle.

The most obvious concern is properly maintaining the battery pack. If the Roadster is left unattended and without power for weeks or months, the battery back will slowly discharge until the pack is fully depleted. If this happens, the battery pack may be ruined. Even if plugged in, if power is interrupted by a popped breaker, extended outage, service disconnection, etc., permanent damage to the battery pack can occur.

Also of concern is temperature. The Roadster should not be left unplugged in extreme temperatures. If the battery pack gets hot, it should be plugged in so it can cool. Consult the owners manual for more information.

Charging

Level 1 In the United States and Canada, the Roadster can be charged at 120V with a simple cord sold as the MC-120. It just connects the car to power with no EVSE logic and the car assumes a 15A circuit suitable for charging at 12A. At this power level, the car can't run the full cooling system and in fact uses a lot of the power just to run the coolant pump. This means a slow rate of charge, and in fact in hot weather, may use all of the power just trying to cool the battery pack. In comfortable weather, not too hot and not too cold, and no rush to get charged, this can be an effective way to charge. Some owners used Level 1 exclusively. Since the coolant pump tends to run continuously, even after charging is complete, there may be a corresponding reducing in the lifetime of the coolant pump.

Level 2 charging means connecting to 240V single-phase power using an EVSE that communicates the maximum current draw allowed for the circuit. It uses the same communication protocol as standard J-1772 charging stations. Having more power means the battery pack can be better thermally managed, which can make quite a bit of noise when the fans, compressor and pumps are all going full tilt. The maximum charge rate of the Roadster is 240V/70A. Unless we were in a hurry on a road trip, we generally charged at 240V/32A which yields good energy efficiency and may be nicer to the battery.

The Roadster can charge from a standard J-1772 station with an appropriate adapter. Tesla sold one for a while and there's an aftermarket adapter.

Charge Modes

The Roadster has four charge modes, used for different purposes.

Standard Mode limits charging to the middle 80% of the battery pack, not letting the charge level get too high and warning the driver, and even shutting the car down, before getting critically low. This is the mode used for daily charging of a Roadster that's driven locally with some regularity.

Range Mode opens up the full charging range, allowing a higher state of charge and enables driving down to a lower start of charge. Range mode also limits power from the pack, and thus reducing maximum acceleration in the name of extending range. Occasional range mode charging didn't seem to have a negative effect on our battery pack, but charging frequently to the top of range mode may accelerate the loss of battery capacity. When we owned a Roadster, we'd do a full range mode charge at the start of long road trip, then switch over to standard mode for driving.

Performance Mode uses the full charging range, allows the battery to get warmer while charging, and allows maximum power (full acceleration). This is appropriate for driving on a track, but probably accelerates loss of battery pack capacity if used often.

Storage Mode displays the state of charge like Standard Mode, but will let the state of charge drop to around 30% then will maintain that level of charge. This is the best mode to use when the Roadster won't be driven for weeks or months. The car must be plugged in to maintain the health of the battery pack. The disadvantage of Storage Mode is that if the power supply is interrupted, it will start discharging from around 30%, so it will get into trouble sooner than if left in Standard mode. That's probably more of a concern if it's in long term storage and ignored vs. being kept for the winter in your garage where you'll notice of the power goes out or the breaker gets tripped.

An example charge screen:

The drawing below shows how to interpret the state of charge in the two main charge modes. Range values are for the original 53 kWh battery pack when new.

Vehicle Log

The Roaster maintains a detailed internal log which can be downloaded via the USB port in the console. Although the format of the logs isn't documented by Tesla, various owners have been able to decode and extra a great deal of data. The log file has two sections: a long term section that has basic info and a more detailed section of recent driving and charging. See the page on the VMSParser I created for more information.

Remote Monitoring

The Roadster did not have support for remote monitoring, not at all for the 2008 (v1.5) Roadster and nothing driver-accessbile for the 2009 and later (v2) Roadster.

There is an aftermarket system availble, the Open Vehicle Monitoring System or OVMS. OVMS allows for remote monitoring of charging, GPS tracking, custom charge settings, and viewing battery metrics. In addition to allowing manual remote monitoring, it can also send low-battery alerts and unexpected motion alerts if the car moves not under its own power.

More Resources

There are a number of other entries on the blog detailing our adventures with the Roadster, plus another collection of longer Roadster articles of practical and historical interest.

The Tesla Motors Club forum is the best community resource around, although its focus has natually shifted to the newer Tesla vehicles.

Charging an electric vehicle is pretty easy: just like my cell phone, I plug it in when I get home and it's fully charged in the morning. It doesn't matter how long it takes because I'm not waiting for it to finish; the car just charges up and waits for me.

Cathy and I took an 1,823-mile electric vehicle road trip to attend the Plug In America board meeting in Berkeley, CA, on June 23rd, 2012. Ever since we took delivery of our Tesla Roadster in June of 2009, I've wanted to take it on a long road trip just to have the experience. Over the past three years, the challenge of making the drive from Seattle to California has been greatly reduced. When Rich Kaethler took delivery of his Roadster in San Carlos, CA, and drove it back to Seattle in August of 2009, and Chad Schwitters made his long trek from Seattle to San Diego and back in April of 2010, these were pioneering efforts. Now we have full speed (240V/70A) Tesla charging along I-5 from British Columbia to southern California, which makes it possible to do the Seattle-to-San Francisco drive electrically in just a couple of days.

Tesla Motors was the first automaker to sell a production electric vehicle based on lithium ion batteries, the Tesla Roadster. Current Roadster owners as well as other prospective electric vehicle owners are interested to know how these batteries will hold up over time and miles.

It's still pretty early in the game. Tesla Motors tells us that we should expect to have our battery packs holding 70% of their original capacity after 5 years or 100,000 miles. The oldest Roadsters are a bit over three years old and some vehicles are getting up into the 30,000+ mile range.

How are the battery packs holding up so far? I've collected data from 20 owners in the Pacific Northwest to get an approximate idea of our batteries are performing.

Before we dive into the results, I should explain a bit about how battery capacity is instrumented on the Roadster. The Roadster has two primary charging modes. Standard mode charges up to about 90% of the pack's capacity and holds the bottom 10% of the capacity in reserve. Range mode fully charges the battery pack and shows the full range available, including the bottom 10%. The range is shown in two ways, "Ideal Range" and "Estimated Range." Estimated range states the range based on recent driving history and so can't be compared across vehicles. Ideal range shows how many miles you can drive in the current mode if driving with the same mixed city/highway average energy use that gave the Roadster its EPA -rated 245 mile single charge range. The corresponds, for example, to driving 55 to 60 mph on level freeway in moderate weather.

First, let's see how miles driven affects battery capacity.

The red squares at the top of the graph show the range mode capacity expressed in ideal range miles (aka ideal miles) versus miles driven on each battery pack. The blue diamonds show the standard mode range. The straight lines show the tread for each set of readings. I interpret this graph to show that for this set of vehicles, individual variation between cars is larger than the pack degradation over approximately 30,000 miles. For range mode, the variation between cars is as much as 15 ideal miles between cars with comparable mileage, while the linear trend shows a drop of only 5 ideal miles across 30,000 miles of driving. For standard mode, the variation between cars of comparable mileage is under 10 ideal miles while the trend line shows a drop of perhaps 6 ideal miles.

Lithium ion batteries lose capacity over time even if you don't use them. The graph shows the same vehicles over time instead of miles.

Again, we see the same apparent patterns: variation between vehicles is larger than the average range lost over three years and variation in range mode is larger than the variation standard mode.

While this is enough data to see some patterns emerge, it's a small fraction (about 1%) of the total Roadsters on the road. I'd like to collect more data to confirm these trends and also separate the effects of time and miles. Most of the Roadsters in this set are in the relatively mild coastal climate of Oregon, Washington and British Columbia. It would be interesting to analyze data from Roadsters in more extreme climates.

Cathy and I were invited to show our Tesla Roadster in the Eco-Center at the 2011 Portland International Auto Show. Tesla Motors didn't have the resources to participate, so we and Chad Schwitters agreed to show our cars and represent Plug In America in promoting electric vehicles.

Cathy and I, with help from Dave Denhart and many others in the Tesla and broader EV communities, have converted our 2008 Roadster and Tesla High Power Wall Connector to use the new industry standard J1772 inlet and plug. This will allow us to charge without an adapter at the tens of thousands of Level 2 charging stations that will be installed in the US by the end of 2011.

What we have is functional and completely reversible, but not ideal; we view this as a version 0.9 conversion. As there are very few J1772 charging stations currently installed, and the numbers probably won't take off until late spring or early summer, we have time to develop a better solution before it actually becomes compelling for Tesla owners to convert in significant numbers. I'm sure Tesla Motors could do a much better job of creating an integrated solution and I would prefer that to having the owner community develop a conversion solution.

We've hear rumors that Tesla is developing an adapter, but are still waiting for official word on what, if any, J1772 solution they will provide. While an adapter would give us a way to charge, we have heard from many owners who would prefer to convert their vehicles and charging equipment to the industry standard rather than leave an expensive adapter vulnerable to theft while charging.

Our effort started last summer when Cathy and I began working with Dave to figure out what it would take to build an adapter that would let a Tesla Roadster charge from the Level 2 J1772 charging stations. We discovered that SAE adopted Tesla's extension to the older J1772 communications standard, so a simple pass-through connector that converts Tesla's charge inlet to the J1772 inlet will allow charging to occur, although there is an issue, which is explained below.

Once we understood the protocol, Cathy and I built and tested a pass-through adapter. When I let the Tesla owner community know about our adapter in mid-September, I wasn't surprised to hear that lots of owners were thinking about those thousands of chargers, but I was surprised how nearly all who expressed an opinion agreed with us that the right way to do this was just to convert the Roadster to use the J1772 inlet. From what I'm hearing from new and prospective owners, it seems to me that many potential Roadster customers are put off by the Tesla plug and this is probably already becoming a barrier to sales.

In the absence of any word from Tesla Motors about a J1772 upgrade path, we've been slowly working toward doing a conversion ourselves. A few weeks ago, we finally obtained an ITT Canon 75A UL-approved inlet and plug pair from Clipper Creek. The plug cord is intended as a replacement cable for Clipper Creek's model CS-100, and carries the same power and signal wires as the TS-70 aka Tesla's High Power Wall Connector (HPWC, formerly the HPC). Clipper Creek also sells a holster for the J1772 plug that can be used to replace the holster for the Tesla plug.

With the necessary hardware in hand, we starting tackling the engineering challenges in getting the inlet mounted inside the Roadster's charge port: there's limited space to work with and the Roadster wasn't designed with the shape of the J1772 plug in mind, so getting the plug and cord to clear the body is tricky. It took a bunch of measuring, brainstorming, numerous experiments, a couple of laser-cut bracket prototypes, some Dremel work on the inlet cup, and then an adapter designed in CAD and printed on a 3D printer to get something functional.

This is what the back of the upgraded inlet port looks like. The blue piece is the mounting plate Cathy designed in CAD and we fabricated on a RepRap 3D printer at Metrix Create:Space.

Here's the work in progress just before installing the J1772 inlet and putting it all back together:

Here's the inlet mounted in the Roadster's charge port:

The ITT Canon cord plugged into the Roadster's charge port:


Charging from our HPWC, now converted to J1772.

The top of the inlet tilts back to angle the J1772 cord up. This works pretty well for the ITT Canon cord with enough clearance at the top of the port that it's easy to slide the plug in and engage the lock, easier than plugging in the Tesla connector in fact. The rubber strain relief on the cord barely rests on the body, plus our Roadster has the paint guard protection there, so I'm not worried about that minor contact damaging the paint.

It's not quite as nice with the plug and cord used by the ChargePoint Coulomb chargers, but I think it's OK for use on the occasional road trip.

In addition to the cable clearance issue, there's another concern with our v0.9 conversion strategy that has to do with the largest difference between the Tesla and J1772 communication protocols.

The Tesla plug uses four contacts: two for power, one for ground and one for the pilot signal. The pilot signal is a low-voltage communications protocol that allows the charging equipment to tell the car the maximum amperage supported and allows the car to ask for the power to be turned on and off. The pilot signal is not connected to the car until the plug is connected and the locking switch is engaged. This switch plays a second role: if the driver tries to remove the plug in the middle of a charge, sliding the switch back interrupts the pilot signal which tells the car to stop charging. This happens very quickly so that the driver cannot get the plug untwisted and removed to break the electrical contacts while current is still flowing. It's important to prevent this because doing so can cause arcing, which would damage the contacts.

Instead of interrupting the pilot signal, J1772 uses a fifth wire for this purpose. Like the Tesla plug, the locking mechanism on the J1772 plug makes the proximity connection, so that when the driver wants to remove the plug and slides the lock it interrupts the proximity connection, thus telling a J1772 car to stop charging immediately (within a tenth of a second). Unfortunately, the locking switch on the J1772 plug doesn't interrupt the pilot signal.

With our v0.9 conversion (or a simple pass-through adapter), the driver can unlock the J1772 plug without the car knowing, and then pull the plug while power is flowing. Cathy and I need to make sure we don't do that. To solve this issue, we need to design a circuit that watches the proximity pin and interrupts the pilot signal when the J1772 plug is unlocked. I don't expect this to be difficult, but we haven't done it yet.

We have already made some improvements in the design. This is version 3 of Cathy's inlet mounting plate design, which we plan to print for our next revision:

In addition to the improved mounting plate, our next steps are:

1) Hope that Tesla Motors provides an official conversion solution before it matters to most owners, thus saving us the remaining steps.

2) Design a circuit to monitor the proximity pin and disconnect the pilot signal when the J1772 plug is unlocked.

3) Test with other J1772 plugs and possibly work on a better solution for cable clearance over the body panel.

4) The 2010 and later Roadsters have the inlet cable assembly connecting to the PEM in a different location. There may also be other differences. We haven't looked into it yet and don't know if it will be more or less difficult to convert than the 2008 Roadsters.

5) Before recommending an unofficial conversion to other owners, we'll need to find out how this will impact our warranty. Tesla Motors has been cooperative with our efforts: they sold our group an inlet cable assembly so that we could do the conversion reversibly. We hope they will continue to be supportive rather than forcing us to wait until our warranties expire before being able to effortlessly access standard J1772 public charging stations.

We are about to see a mass deployment of public level 2 SAE J1772 charging stations, over 14,000 from The EV Project alone. This compares to fewer than 100 public Tesla charging stations (240V/70A High Power Connectors, aka HPCs). Over the next 12 months, I expect that the availability of level 2 J1772 chargers will totally overwhelm all other charger types.

While most of these 240V chargers will be limited to 30A or 32A, J1772 chargers capable of supplying 240V/70A are available from Clipper Creek with many other vendors also working on charging stations.

Teaming up with a number of other Tesla owners and members of the broader EV community, Cathy and I have been looking into what would be required to bring J1772 charging support to the Roadster community.

The good news is that Tesla and J1772 use the same communications protocol to establish the connection and start/stop charging. This didn't happen by accident. Tesla Motors was involved early on in the development of the J1772 spec. But the Roadster was designed before the new J1772 committee even got going, so the Tesla charging protocol was designed based on the old J1772 specification which used the Avcon connectors and limited charging to 40 amps. Tesla extended this protocol up to 70 amps, and successfully lobbied the J1772 committee to adopt this extension. Cathy and I have confirmed that the SAE J1772 JAN2010 spec exactly matches the amp limit waveforms produced by the Tesla HPC at all amperage limits from 12A to 70A.

So, the Tesla Roadster uses the same communications protocol as J1772. (Except for the button on the HPC that can be used to start charging; I don't know how that works.) The only barrier to charging a Roadster from a J1772 station is the Tesla plug. We confirmed this by building a proof-of-concept adapter and using it to charge our Roadster at a Level 2 J1772 charging station in Olympia, WA, last Friday (Sept. 10, 2010).

We'd like to thank Dave Denhart, Rich Kaethler, Chad Schwitters, Martin Eberhard, and Dave Kois for helping us with this proof-of-concept project. Thanks also to Jim Blaisdell of Charge Northwest for helping us find a level 2 charging station and getting us a ChargePoint Network card overnight. Our crude adapter is not a robust solution. As you can see it's quite bulky (since we didn't want to cut the cable to a working Tesla plug) and isn't watertight enough for general outdoor use.

When the Roadster was entering production, there was no standard J1772 plug, so Tesla had to design their own. That was a necessary step, but now that the final standard uses a different plug, I think we need to find a real solution to this incompatibility. As I see it, there are at least 4 possible solutions:

1. An upgrade to switch both the Roadster and HPC to use J1772 connectors.
2. A compact adapter that converts J1772 to the Tesla connector.
3. A new pigtail for Tesla's universal mobile connector (UMC).
4. A new pigtail that requires purchasing a re-engineered UMC.

A new pig tail for the current UMC (solution 3) isn't very appealing as the UMC is limited to 40A, cutting us off from any 70A J1772 chargers, while also requiring us to stuff a large, heavy, awkward cable into our trunks just to charge at a station that is guaranteed to have a cable that will reach our charge port. It's also not nice for those of us who have already invested in a different mobile connector, like the original MC240 or the RFMC. Solution 4 is even worse than 3 as it shares all of the problems and it would require everyone to purchase a new mobile connector.

A compact adapter (solution 2) is better in that it could support the full 70A charging and also be quite compact, little more than a J1772 receptacle and a Tesla plug. It will still be quite expensive as it requires a Tesla plug. My guess is that it would cost at least $1,200 retail, based on what Tesla charges for the MC240 and UMC. It also has the downside of being an obvious target for malicious theft when the car is left charging unattended. Nissan Leaf owners won't have to leave an expensive, unsecured device dangling from their cars when charging, why should we?

Full conversion to J1772 (solution 1) sounds radical until you see a J1772 receptacle. It's very close to the size and shape of the inlet in the Tesla charge port. Once I saw that, it required zero imagination to picture a Tesla Roadster with a J1772 receptacle in place of the proprietary Tesla charge inlet.

The downside of solution 1 is that it would also require replacing the plug on our home chargers (HPC or mobile connector). This could be done by either replacing the cable, or by using the old Tesla inlet and a J1772 cable to make a Tesla-to-J1772 converter.

The retail cost of an ITT Canon UL-certified J1772 receptacle and cable pair rated for 75A is $825 from Current EV Tech. I don't know of anyone else selling these newly-available connectors, but I do expect it to be a competitive market much larger than just Roadster owners. Even adding in reasonable labor costs, it seems to me that converting a Roadster and HPC should be near or below the cost of a J1772-to-Tesla adapter.

I have been told that Tesla Motors is investigating ways to bring J1772 support to the Roadster which may include either a compact stand alone adapter (option 2) or a J1772 pig tail for the Tesla universal mobile connector (I'm not sure if this is option 3 or 4). They are early in the process and not promising anything at this point. From what I have heard, Tesla Motors is not interested in providing a full J1772 conversion (option 1) and hasn't even committed to supporting J1772 on the Model S.

It's possible the full J1772 conversion could be done even if Tesla Motors doesn't give us an official way to do it. I expect our group will continue exploring ideas in case we have to tackle the problem ourselves.

We are several months away from having a significant number of Level 2 J1772 chargers installed in metro areas targeted by The EV Project, and even further away in other areas of the US. There's plenty of time left for both Tesla Motors and the owner community to explore possible solutions, but I believe this will soon be an important issue for every Roadster owner who wants to be able to take advantage of the soon-to-be pervasive J1772 charging infrastructure to conveniently drive beyond the Roadster's single charge range.

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.

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.

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