By on January 25, 2010

Former Tesla PR man Daryl Siry’s Autopia columns are always good for some interesting insights on the EV world… as long as you take them with the grain of salt that Siry’s status as “advisor” to EV startup Coda Automotive demands. This week Siry has it in for the mass-market EV frontrunner, the Nissan Leaf, accusing its makers of “cutting corners” and “overpromising” range specs. According to Siry:

First, Nissan overpromised on the realistic range by consistently quoting a number tied to the most optimistic benchmark, the LA4 cycle. Drivers who stick to stop and go traffic on city streets in temperate climates may indeed consistently see 100 miles of range, but most drivers will see significantly less in a mix of city and highway driving. Driving in California, the country’s top market for electric vehicles, involves a lot of time on highways where the 65 mph speed limit is rarely observed. The LA4 cycle Nissan quotes mostly stay below 30 mph with one two-minute “sprint” at 55 mph every 22 minute cycle.

But wait, there’s more!

It also appears Nissan has cut corners on the most critical aspect of electric vehicle technology – the battery pack. The key engineering tradeoff Nissan has made is opting not to include active thermal management, where the temperature of the pack is controlled by an HVAC system similar to what cools the passenger cabin on a hot day. Instead, Nissan has opted to use only an internal fan that circulates the air within the sealed pack to evenly distribute the heat, which escapes by passive radiation through the pack’s external case.

We don’t need thermal management for the U.S., but we are looking at the technology for Dubai and other locations like that… We’ve gone on the record saying that the pack has a 70-80 percent capacity after 10 years… If it wasn’t our pack and it wasn’t our engineers and we weren’t working on it for 17 years… we wouldn’t make the statement
In a fascinating twist, Paul Hawson, a Nissan product planner who worked on the Leaf tells Siry the active thermal management was left off so the Leaf could be a true five-seater. Otherwise, the thermal management gear would split the rear seats, forcing an awkward two-bucket configuration like that of the Chevy Volt.
But, as Siry points out, it gets pretty hot in Pheonix, Arizona, one of the Leaf’s US launch markets. If Dubai is a concern for Carlos Ghosn’s EV boffins, the American southwest probably should be as well. We’ll bet a nomex suit that Nissan has thought this through, and Siry’s just sniping at Coda’s main competitor… but if Leafs start exploding in warmer locales, Nissan’s gamble on EVs will have been yet another auto industry lesson on the dangers of hubris.
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27 Comments on “Siry: Nissan Leaf Has No Active Thermal Management, “Overpromises” Range Numbers...”

  • avatar

    Aerodynamic drag per mile is proportional to the square of the speed. So a vehicle going 2x as fast will require 4x as much energy to go a set distance. In a conventional car, the engine runs much more efficiently at steady-state 60 MPH than it does idling along in city traffic averaging 30, which makes back much of the inefficiency of aerodynamic drag.

    Electrical vehicles have no such problems in stop-and-go slow traffic and they have no such advantages with steady-state high speed driving. So, if the Leaf goes 100 miles at 30 MPH it is likely to only go 25 miles at 60 MPH. Where I live, 70 MPH would put you in the slow lane of the main highways; at that speed you would get (30/70)^2 * 100 = 18 miles on a tank.

    • 0 avatar

      It’s not as simple as you state. Tesla actually has a great graph of efficiency (rather, power usage in Wh/mile) versus speed on their site:

      Also, I would certainly hope that the range figure isn’t quoted as an absolute best case, i.e. at 30 mph, and any company stupid enough to do so will get slaughtered in the marketplace.

  • avatar

    Having designed many thermal systems with both passive and active heat management, I’m impressed that Nissan has chosen a largely passive design. Such a design will certainly reduce cost and complexity, and may actually improve reliability of the entire vehicle since it will inherently possess fewer moving parts, sensors, wires, etc.

    It remains to be seen just how ‘passive’ their design really is. Even simple ducting that can be opened and closed would be a semi-passive design with a few active components. This would enable some level of thermal control without the complexity of an HVAC system.

    Designing a thermal system for electronics, particularly a passive one (but also active) is very difficult given a 100 C temperature swing, or whatever the criterion is. Mr. Perry is correct – having designed it in-house over 17 years (!) means Nissan’s engineers probably have the situation well-characterized.

    Thermal designs are a choice of compromises. Four-seat cars are generally derided as short-sighted. Nissan won’t get that complaint.

    Siry’s criticism about the range – while founded in some reality – does not eliminate the fact that you have to evaluate using some standardized test cycle. If he doesn’t like the LA4 test cycle, then he ought to suggest another test spec that EV developers can work toward.

    • 0 avatar
      Paul Niedermeyer

      He has, repeatedly. The City cycle is obviously particularly favorable to EVs, and leads to distorted expectations and inevitable disappointment. We’ve written on this subject often, most recently here:

    • 0 avatar

      He has, repeatedly. The City cycle is obviously particularly favorable to EVs, and leads to distorted expectations and inevitable disappointment.

      Will it, though? EVs are inherently urban by virtue of their demographics, just as casual-use half-tons (and bigger) are comparatively rare in the same place.

      I’m sure the Leaf and Volt will do quite well in, eg, Boston or Montreal. Heck, I’d say the Leaf has “Built for Life in Montreal” written all over it.

    • 0 avatar

      PN: Fair enough. But Mr. Siry ought to focus his energies on herding the cats that are EV makers, so that there is agreement on a range standard, rather than criticize the technology of a competitor’s design. Otherwise, in the end, all EV makers will lose. The design criticism can happen in the showroom.

      There is exceptionally high risk to EV acceptance by having no common reporting standard. I’m not against EVs; I think they have their place, despite poor ROI. But what is possible is this: The public, after hearing disparate ranges and driving styles called out (230 mpg!), will simply avoid the products due to the geek-fest arguments that define EVs.

      Frankly, nobody cares about active thermal management, cell chemistry, or battery charge windows, except a few engineers like me.

      Consumers are used to the “city” and “highway” numbers. A similar dumbing-down of EV performance is essential to achieving respect in the market. Ratings for “aggressive driving” vs “gentle driving” might help people understand.

  • avatar

    Hmmmm …. even the electronics expert HP had to recall their laptop batteries for thermal issues – and these are relatively simple compared to ev-technology, use, expected longevity – and laptops (generally) operate in relatively benign environments esp. when compared to automobiles … I’m really wondering what kind of surprises lie in store for ev’s … time will tell…

    • 0 avatar

      The thermal issues that have happened with laptops have been caused by shorts, or charge errors, not because they are insufficiently cooled. While it is true, these batteries produce a lot of heat, there are plenty of high stress applications that use passive cooling…power tools being one.

      Also, internal fans are not passive. Passive would be expecting all the heat to be removed by fins, with no air movement assistance.

      IMHO, they should develop a system that can cool with fans, as opposed to needing energy robbing air conditioning.

    • 0 avatar

      Agree with your comments.

      Battery technology is somewhat outside my field of expertise, but what I mean is, regardless of active or passive thermal management, looking at the size of these ev-battery packs (Leaf, Volt, etc), the complicated package shapes and (multiple) heat-sinks, and then cross this with an automotive use profile and operating envelope (including temperature extremes and environmental contaminants like dust, dirt, salt from air or moisture borne sources – as these cling to and insulate the external surfaces of the heat sinks, heat rejection efficiency will fall dramatically) and I can’t think of any other rechargable battery application that is so challenging.

      And then to cross this with a 70-80% (of new) capacity after 10 years, I think it will be nothing short of amazing if everything goes as planned.

      I’m talking about “unintended thermal events” but even moreso about battery capacity over a 10-year life time.

      The “we’ve been working on this for 17 years” comment speaks of an organization that should be familiar with what they want and what is possible to deliver.

      Given all the changes in battery technology in that time, and the changes in the base chemical formats (e.g. NiMH v. Li-Ion), the reality will lie somewhere between the amazing and familiar of the 2 preceding paragraphs.

  • avatar


    I’m really wondering what kind of surprises lie in store for ev’s

    If we look at the reliability of the Prius I think it certainly possibly that owners could be pleasantly surprised by the reliability and durability of their vehicles. I think you also need to keep in mind how many surprises owners of ICE vehicles encounter: oil sludge, transmissions issues, coil packs, dexcool, intake manifold gaskets, etc.

    ICE while a mature technology, isn’t by nature a simple or reliable one.

  • avatar
    Robert Schwartz

    “EVs are inherently urban by virtue of their demographics …

    … the Leaf has “Built for Life in Montreal” written all over it.”

    Urban? You mean where people live in apartment buildings and park their cars on the street, out of range of electric outlets.

    Montreal? This time of year in Montreal the normal temperatures are a high of -6C(21F), and a low of -15C(5F). How well will your batteries work if the car is on the street and the weather is like that?

    • 0 avatar


      You beat to the punch on this one. EVs are only suitable for temperate climates. Battery performance is greatly effected by temperature. Too cold and you get less energy flow out of the battery and if it’s too hot battery life suffers as well as range. Heat is the enemy of battery life.

      A note to JMO: The Prius charge cycle keeps the battery charge between 50 and 70 percent. This is done to maximize battery life. Pure EVs will draw down the battery to very low energy levels. This will kill the battery’s life. Charging up to 100% will overheat the battery and shorten it life.

      Bottom line: If an EV has a theoretical 100 mile range it’s practical range in temperate climates is about 80 miles and far less in cold climates.

      Our current craze for pure EVs requires a repeal of the laws of thermodynamics. Not going to happen. As much as I hate GM they have taken the correct approach with the Volt. There concept is a proven method of using electric propulsion. The last class of US diesel-electric submarines (USS Barbel, USS Bonefish and USS Blueback) ran all propulsion through the battery even when the diesel engines were used.

    • 0 avatar

      No, urban as in “I’m single, live in a condo or apartment with a subterranean garage, make six figures, and if I commute, it’s to the grocery store once a week”.

      Eg, places where street parking is functionally non-existent for traffic reasons.

  • avatar

    This has been under development for 17 year and Nissan claims the battery will still be at 80% after 7 years.

    With current technology EVs will only appeal to a certain subset of customers. Just like a Miata or Boxter or Corvette doesn’t appeal to people with kids, people who need to tow a boat, etc. the Leaf will only appeal to the small subset of customers for whom it makes sense.

  • avatar

    Nissan has not been developing its battery pack for the Leaf for 17 years. In the early 2000s, as a cost-cutting measure, Nissan abandoned all electric vehicle development and transferred or fired its people. The Leaf battery pack has been developed recently.

    So no one knows how long the Leaf battery pack will last. Will it have 70 to 80% of its capacity after 7 years? Possible. But very doubtful. That kind of battery life has not been seen to date, and seems, as a practical matter, impossible in this kind of application.

    Particularly with the heat problem. Explosions are not the issue. Battery life is. The US military is finding in Iraq that heat affects even lead-acid batteries. But not keeping the Leaf battery pack cool may well turn out to be a mistake for Nissan. Battery life, for some people at least, may be measured more easily in months than in years.

    • 0 avatar

      Accelerated duty cycles at elevated temperatures are easy to test with the existing equipment owned by any major automaker. I find it hard to believe Nissan would test market the Leaf in Phoenix if they knew their batteries would systematically fail within a matter of months.

    • 0 avatar
      Rod Panhard

      It’s easy to focus on “battery life” at this point of the discussion. Keep in mind that batteries are still heavy, regardless of the type used. So to make up for the batteries’ weight, other weight has to be removed from the vehicle. As a car enthusiast who has been known to roam u-pull-it lots, I’ve seen situations where, if a part had been made a bit more durable, it would have weighed more.

      Point being, it won’t matter how long the batteries last if the rest of the car is not up to the task. Welcome to yet another automotive “chicken & egg” conundrum. Electric cars make sense in dense urban markets where distance range matters less than time range. What remains to be seen is if the electric car shopper is considering the use of said vehicle to get from his garage to the train station. And if so, how much more will it cost than the classic “station car” or “airport car” that costs relatively little.

  • avatar

    Battery life, for some people at least, may be measured more easily in months than in years.

    So, you think they did the usual automotive hot weather testing and the battery only lasted weeks? Somehow I doubt that.

    • 0 avatar

      No, I’m saying that lithium-ion batteries will often lose 50% of their capacity in less than 2 years time.

      Each battery chemistry has its quirks. With lithium-ion, batteries permanently lose about 1% of their capacity per month, starting as soon as they are made in the factory. That’s under the best of circumstances. If the batteries are not pampered, that rate can raise to 2%, or even 3% or more. Per month.

      So you might have a lithium-ion battery that loses 50% of its capacity in 18 months. Particularly when, as with Nissan and its “passive cooled” prismatic batteries, you can bet that some people will not keep their batteries cool. Like running a horse hard and putting it away wet. Scary to think about.

    • 0 avatar

      There are many different Lithium chemistries…many with much improved lifetimes then those first generation Lithium Ion cell phone and laptop batteries. Those batteries would easily lose 10-20% of their capacity a year and some were only good for 150-300 full charge cycles. For example, Dewalt uses A123’s Lithium FE cells in their power tools. This is a technology that was developed at MIT, that greatly improves temperature capability and durability. If I recall, Chevy had partnered with A123 for the Volt’s batteries. Sony and Sanyo are working on similar technologies as are other manufacturers and universities.

  • avatar

    I’ve reluctantly moved towards the “Volt Camp”, as battery chemistry is too finicky to be relied upon without the huge cushion provided by severely limiting the working capacity and having an ICE on-board. The Prius plug-in is even being carefully considered by Toyota, due to the necessity for Li-ion batteries to achieve the goal.
    FWIW, I believe that the Leaf’s Li-ion pack will be leased separately from the car.

  • avatar

    Perhaps it would be a good time to investigate Peltier devices or some other form of electric waste heat recovery to help manage battery heat – the only issues is that these need a +ve temperature gradient from source to ambient so this would help in the south!- back to the drawing board!

  • avatar

    I really think “EV’s” are much more practical in the motorcycle world:

    $7-$10k for a bike vs $40k+ for a car

    A LOT less emissions from an electric motorcycle vs std motorcycle, as opposed to comparing an electric car vs a standard car.

    People don’t expect to take cross country trips on dual sport or basic street bikes (I don’t know of any touring electric bikes) or scooters. People expect to be able to do this in a car.

    People on a bike don’t expect heat/ac on a bike, where they do in a car.

    People don’t expect large cargo space on a bike — they prefer it in a car.

    The only downside is that electric bikes have very short range on the highway currently (20 miles). For urban commuting you are talking 40-100 miles currently.

    • 0 avatar

      I wouldn’t consider that the only downside. Many people (rightfully) think that bikes are much more dangerous than a car. So if you don’t mind being squashed by something with 18 wheels, sure, get that EV bike.

    • 0 avatar

      Pretty much EVERYTHING gets squashed by an 18 wheeler. That is not specific to motorcycles.

      I also think you missed my point completely:

      1) motorcycles in general produce much/many more bad emissions than cars (since most IIRC don’t even have cats. I know here in IL there is no emissions testing for motorcycles). The amount of pollution saved PER unit on an electric motorcycle vs a conventional one should be much greater than an electric cars vs a standard car. On top of pollution to actually create & dispose of the battery (since there are less batteries) used for a bike should be less than that of a car. Zero Motorcycles says their battery is so safe you can actually eat if you want to.

      2) The “price premium” for an electric bike is not higher (in raw, not in %) than a standard bike. There are several companies with products that you can purchase right (& register) right now that are street legal. Prices are low as $8k for entry level. People already pay more than that for a 600cc sport bike, harley, goldwings, or midsize cruisers.

      I’m not arguing cars vs motorcycles for safety. I’m arguing that electric motorcycle vs conventional motorcycle makes more sense (emissions & price-wise) as opposed to std car vs electric car. It doesn’t make sense purely from a “I-need-to-save-gas-$” perspective since most motorcycles are 40-50+mpg already.

  • avatar

    Montreal? This time of year in Montreal the normal temperatures are a high of -6C(21F), and a low of -15C(5F). How well will your batteries work if the car is on the street and the weather is like that?

    Most part of Canuckstan has this kind of similar weather,
    At -15 c wonder how many 7-11s can u pass before u make it to work, I bet u do need a plug in at work just like most Parking facilities in Winnpieg , Regina etc. But these parkings were only supplying u enough current of 100 – 200 watts block heater. 1 EV charging will = to a dozen of regular cars block heater consumption.
    The Equation of consumption will get upset pretty quick!

    What would u do when u run out of Juice in a EV on the autobahn?
    EVs are like bicycling, one cannot push it when high on energy or else u will have to gimp home painfully.

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