No Active Thermal Management: Did Nissan Make the Right Call?

Tom Moloughney · Tom Moloughney · 1 year ago

After 14 months and 37,000 miles of driving my MINI-E, there is really only one glaring flaw that I can find with the car (besides only two seats that is): The lack of a sophisticated thermal management system.

As much as I love the car, and I really do love it, the passive air-cooling battery system is woefully inadequate for the hot summer days, as well as the cold New Jersey winters.

I'm not complaining. The MINI-E is is a prototype test mule—a car that was designed for an internal combustion engine and was retrofitted with a 35 kWh battery pack and an electric drivetrain. I knew there would be occasional problems and that the car wasn't really "production ready" when I agreed to be in the trial lease program. That said, the car has performed admirably and only needed to have two of its 48 battery modules replaced so far. I knew the lack of a thermal management system would affect the car's performance, and I accepted the possible inconveniences so I could have the opportunity to drive an electric car for a couple years.

Ready for Prime Time?

On the other hand, I'm not so sure Nissan LEAF customers will be as forgiving if the car falls short of expectations in extreme temperatures. Buying a $32,000 car is much different than agreeing to be part of a beta test for one or two years. Nissan has been defending its decision to sell the LEAF with basically the same temperature management system the MINI-E has—fans that blow cabin air across the pack to cool or warm it.

I really hope they have made the right decision. I really am pulling for the LEAF. I want to believe it's ready for prime time. I am hoping that the combination of better battery chemistry and the ability to warm or cool the cabin (and thus the batteries) while the car is still connected to the grid (the MINI-E cannot do this) will allow for better performance than I see with the MINI-E.

When I was at the New York Auto show this year, I grilled the Nissan representatives about this—so much so they really just wanted me to leave. Although they were steadfast in saying, "We are confident the LEAF will perform well in all ambient temperatures," I did get one person to concede that they are working on an active thermal management system and could possibly be an option for the Generation 2 LEAF for regions that are particularly hot or cold. Ah, so they are a little worried.

Warranty In Place

Recently, the CEO of Tesla said the LEAF's battery is "primitive." Strong words from someone that really isn't in competition with Nissan just yet. However, it did put the spotlight on Nissan and I think they need to make some kind of statement as to why we can feel confident that the car isn't under-engineered. The 8 year / 100,000 mile warranty is a good step in the right direction and shows confidence, but I think Nissan needs to be a little more forthcoming about why they decided to omit what just about every other auto manufacturer believes is necessary in an EV.

I have recorded battery temperatures as high as 119 degrees on my MINI-E and performance really suffers when the temperature gets above 105. In fact, the car refused to charge a few weeks ago because the batteries were too hot. Additionally in the winter, the range gets reduced by about 25% when the temperatures drop below 40 degrees. I have even had a few extreme instances on really cold days where the range was reduced by as much as 40%. Again, all this is acceptable for a prototype test car, but how will people react if this happens with the LEAF?

Comments

· TrasKY (not verified) · 1 year ago

Good article. I don't know if one can conclude that the Nissan is worried about the battery so much as aware. Electric cars have a lot of doubts and doubters to overcome. Nissan has publicly promised a delivery date and made strong implications about the general price range. So they need to get these out the door, even if the second generation battery won't be ready until folks start to complain about the first generation batteries. Then they'll sub out the batteries, free of charge, take the loss and brag publicly about their new battery design and this will all have been a blip.

· ex-EV1 driver · 1 year ago

Thermal control is a big issue with EVs in general. Since the challenge is so much easier than with an ICE, its design often gets overlooked. Remember that an ICE is only about 20% efficient so 5X as much energy as pushes the car down the road must be shed as heat. EVs are over 90% efficient so ony 10% of the energy that moves the car down the road must be shed, however that still is a few kilowatts of power. The limiting performance factor, even with the Tesla Roadster is thermal. While the batteries have been well designed with active cooling, the Power Electronics Module (PEM) and motor will overheat in extremely heavy driving (track racing with maximum acceleration and speeds).
While I never would buy an EV from a small company such as Tesla without a solid story on battery cooling, we can probably be confident that Nissan has the resources to stand behind their battery warranty if they have under-designed their thermal management system.

· Anonymous (not verified) · 1 year ago

And yet GM engineers covered this in the new Volt with their liquid thermal management system. Check out www.voltage.com for documentation of the EXTREME temperature testing GM put this car and its batteries through. The Volt is a MUCH better engineered vehicle than the Leaf. Imagine that, Asian manufacturers cutting a MAJOR corner with their "halo" electric vehicle, while an American car manufacturer has over engineered the heck out of theirs! Way to go GM!

· Tom Moloughney · 1 year ago

Yes, it would seem as though GM has done a great job of engineering the volt. Hopefully they will come out with a BEV version soon. There has been many reports that they are working on one and even Bob Lutz indicated that they will sell one, just no timetable when. I'd love to see the volt with a 32kwh pack and increase the usable battery range from 30/80 to 25/85. The car would probably get 100 to 120 AER and still last a long time with the thermal conditioning. It would be incredibly simple for them to do since all the major engineering is already done. Here's the article from Car & Driver: http://blog.caranddriver.com/pure-ev-chevrolet-volt-in-the-works-accordi...

· Kei Jidosha (not verified) · 1 year ago

You can’t have it both ways. Air cooled batteries are half the cost of liquid cooling. A 32kWh BEV with the Volt’s technology is $30k for just the battery. What is the market for a +$55k Volt?

It remains to be seen if the LEAF battery chemistry is more robust than the MINI E’s. If not, Nissan will have a problem. But the reliability of the Volt’s complexity is also unknown. So the Volt and Leaf may both need to improve. The LEAF to compete on temperature range, the Volt to compete on price.

Both cars will have their market. But for me, simpler is better if Nissan can make it work.

· Tom Moloughney · 1 year ago

I want to be clear, I'm not LEAF bashing with this post. I'm hoping that since this can has been designed ground up as an EV, unlike the MINI-E it will perform better in hot and cold climates. Nissan may very well have designed the passive thermal management system to work better and combined with more advanced battery chemistry may work just fine in all but extreme conditions.

"Kei" is right that there is definitely a trade off with cost and performance. I wouldn't be the first one to rush out and buy a LEAF if I lived in South Florida or the Arizona desert, much less Fargo, ND. However you can't expect it to be everything for everybody and we'll have to see how these cars actually handle temperature extremes. I'm sure in many parts on the country the car will perform just as advertised or Nissan wouldn't have given it such a robust warranty.

I'm rooting for both of these cars to succeed, I think if either proves to be mechanically unsound or of inferior workmanship than the EV industry as a whole may suffer.

· Nick Chambers · 1 year ago

"I'm rooting for both of these cars to succeed, I think if either proves to be mechanically unsound or of inferior workmanship than the EV industry as a whole may suffer."

Absolutely agreed! I even wrote a post about just that issue a while back. And it's not just restricted to Nissan and GM... Mitsubishi and Ford will also be getting into the game before everybody else (albeit later than Nissan and GM). In this world held in the stranglehold of the oil lobby and America's apparent lack of desire to be rid of that stranglehold, there will be (and already is) a ravenous appetite to prove that EVs don't work, so any foothold that crowd can use to prove their point will be exploited to the utmost.

· ex-EV1 driver · 1 year ago

Kei,
I hardly think that a cooling system, after development costs are fully amortized, should cost $15K. One can buy ICE vehicles today for around that cost for the whole car and I'm sure their cooling system doesn't cost $15K, even though it must reject about 5X as much heat.

· evnow (not verified) · 1 year ago

I can't seem to find it - what is the chemistry of the Li battery Mini-E used ?

· evnow (not verified) · 1 year ago

"I want to be clear, I'm not LEAF bashing with this post."

I don't know whether that was your intention or not. Doesn't matter. That is exactly how GM is using this post. They have linked it in their Facebook page.

It is interesting that GM is using 50% DOD - and liquid cooling. They give 8 yr warranty. Nissan uses basically the same battery chemistry, much more DOD, air cooling and yet gives 8 yr warranty. Either GM has over-engineered (which shows in their $41,000 tag) or Nissan with their 17 years of Li battery experience has under-engineered and yet are willing to take a huge financial risk by giving 8 year warranty. Hmmmm.

· evnow (not verified) · 1 year ago

@ex-EV1 driver

Liquid cooling was going to cost Leaf its back middle seat. That is what I read.

I think it likely 2012 Leaf will have some way to heat the battery - I suspect that is the reason 2011 Leafs will be only sold in warmer regions of US.

· evnow (not verified) · 1 year ago

Sorry to say, this is a poor article comparing standard laptop style Cobalt oxide batteries used by AC Propulsion for Mini-E to the prismatic Li-Manganese batteries used by Leaf. Ofcourse, laptop batteries need proper liquid cooling like Tesla does. They are also ...thermally unstable ...

Li-Manganese batteries that Leaf & Volt use are a different story. They have excellent thermal stability. They are not little cylinders - they are large flat format which dissipate heat very easily. No need for complex, expensive liquid cooled batteries.

One more thing. LiMn batteries have low internal resistence. So they don't get as hot as the laptop batteries ...

Note that, for all this bravada by Tesla, their new batteries from Panasonic are not Li Cobalt oxide ones. They are Li Nickle.

Here is the ABG article on AC propulsion batteries : http://green.autoblog.com/2008/11/19/la-2008-confirmed-ac-propulsion-pro...

· Anthony (not verified) · 1 year ago

I think it is a very good comparison. Actually, it's probably the best comparison that anyone could make.

The mini is currently the only electric car in any significant number (about 650 of them) on the road today that has a similar air cooled system with a lithium ion battery pack. Sure the chemistry is different and the author pointed that out. He also pointed out that the leaf is better engineered and should fare better that the mini does because it can be heated & cooled while still grid connected and that it was developed as a pure EV, not a converted ICE glider.

There are no electric cars currently available that are using the same LiMn chemistry that the leaf will so we really don't know how well they will work in extremely hot or cold weather. We can guess how they will perform based on how they have worked in the lab, but it's not until there are hundreds and then thousands of these cars out there in the real world will we know exactly how well they will handle extreme temperatures. Until then, all we have are comparisons like this.

Nice insight Tom.

· ex-EV1 driver · 1 year ago

@ evnow,
I'm not sure where you heard that active cooling would require sacrifice of the back middle seat. That sounds like an interpretation of why the Volt doesn't have a back middle seat but the Leaf does. My interpretation is that GM stuck with the same centerline battery tunnel with a "T" shaped battery pack like the EV1. I'm pretty sure I could engineer a few cooling tubes through the Leaf's under-floor batteries and to the cooling chamber of the HVAC unit like Tesla does without sacrificing the back middle seat.
Regarding your statement:
They are also ...thermally unstable ...
That's a pretty harsh accusation for a commodity product that millions of people carry around all the time today, including on airlines where 'thermally unstable' would be catastrophic.
I fully agree that different Li-ion chemistries are likely to be much better if they are designed solely for EV use.
We're doubtless going to learn a lot and see huge improvements as EVs start rolling off mass-production lines in large numbers. Right now, we're just a bunch of pundits predicting the outcome of the big game during the pre-show. All we know is that it is likely to be a good game.

· Kei Jidosha (not verified) · 1 year ago

ex-EV1 driver

$350/kWh vs $700/kWh. Some day, less;

http://earth2tech.com/2010/08/05/tesla-ceo-nissans-leaf-battery-is-primi...

· Tom Moloughney · 1 year ago

evnow: I got a few emails about the Facebook link, mostly questions about the effects of cold weather though.

Your comment: "It is interesting that GM is using 50% DOD - and liquid cooling. They give 8 yr warranty. Nissan uses basically the same battery chemistry, much more DOD, air cooling and yet gives 8 yr warranty. Either GM has over-engineered (which shows in their $41,000 tag) or Nissan with their 17 years of Li battery experience has under-engineered and yet are willing to take a huge financial risk by giving 8 year warranty. Hmmmm." is basically what I was saying, that it is interesting. Who has made the right decision? There was no bashing, just wondering.

· TechExplorer (not verified) · 1 year ago

I'm a Fan of the Nissan Leaf and others,but I do have concern over the thermal effects with the battery pack,i live along the gulf Coast and just the other day was 106 with heat index of 116.

· ex-EV1 driver · 1 year ago

@Kei,
That article does not say what Tesla pays per kWhr for their liquid cooled pack.
@TechExplorer,
I understand your concern and share it to an extent too since I live in the Southwest where I've driven a Tesla Roadster up a 10% grade from 4000 ft elevation to 5000 ft elevation in 118 degree air temperatures.
Nissan may take a bath on their decision. The good news is that Nissan can probably afford to replace a few battery packs early on while they learn what shortcuts they can or can't take. The first owners will not have to share that risk with Nissan.
Note that on my heat stress testing (above) of the Tesla, my expensive battery pack remained nice and cool. The air cooled Power Electronics Module (PEM) over-heated and reduced my power until I wiped it down with a damp cloth. FWIW, it was a 1st generation Roadster 1.5. The Roadster 2.0 and 2.5 have more aggressive cooling of the PEM.

· A2_Leaf (not verified) · 1 year ago

I'm a LEAF enthusiast, having reserved one on the first day you could do so. However, I share concerns about the car's lack of a thermal management system. I live in Michigan, where summer high temps occasionally exceed 90F, and winter lows occasionally dip below 0F. Therefore, my auto needs to operate in a wide temperature spectrum. Michigan isn't an initial Leaf rollout state, so that will provide me the opportunity to benefit from other people's experience.

· Chacama (not verified) · 1 year ago

As I see it, the real problem for us is somewhat simmilar to the world series or the world cup: We all are big time fans of a game called EVs and want badly to see which one of our two favorite teams (LEAF - VOLT) will win the match... if there is one.

· Herm (not verified) · 1 year ago

Nissan engineered their packs mostly for rapid charging, at the expense of weight.. one advantage of this design is that it generates much less heat (low IR losses) when used, the other advantage is the high power (not energy) output of the pack. The LG cells are lighter in weight for a given capacity but they require liquid cooling.. also the power output of the Volt 16kwh pack is probably limited to 120kw.

· SageBrush · 1 year ago

My guess is that Nissan engineered the battery for its expected use, which is urban/suburban driving. GM had to engineer the Volt to climb Pike's peak

Add comment

·

The content of this field is kept private and will not be shown publicly.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Allowed HTML tags: <a> <em> <strong> <cite> <code> <ul> <ol> <li> <dl> <dt> <dd>
  • Lines and paragraphs break automatically.
To prevent automated spam submissions leave this field empty.

All Discussions

States Consider Taxing Electric Cars to Make Up For Lost Gas Tax Revenue

Blog Post · 50 comments

Zach McDonald says:
Politicians in at least three states are reportedly considering the creation of plug-in car taxes. The new fees would...

Tesla Model S Range Exceeds Even Tesla's Expecations

Tesla Model S Article · 7 comments

Eric Loveday says:
According to Tesla Motors, the 85-kWh version of the Model S is expected to achieve 250-350 miles of range during...

Nissan's Fourth Electric Vehicle to be PIVO-Inspired Urban Commuter

Article · 12 comments

Brad Berman says:
Reports suggest that Nissan's fourth electric-only automobile will be a funky high-tech PIVO-inspired urban commuter...

My Treasure

Discussion · 0 comments

lyntornado2012 says:
Is an electric car a good thing?...

Canada's First DC Quick-Charge Station is Now Operational

Article · 8 comments

Eric Loveday says:
Mitsubishi of Canada moved a step or two closer to more convenient charging of its electric i hatchback with the...

Does EV Quick-Charging By the Minute Make Sense?

Nissan LEAF Article · 20 comments

Brad Berman says:
When drivers of gas-powered cars fill up at the gas station, they know they are paying a certain price for a clear and...

Wanted: Fair Costs for Electric Car Home Charger Installations

Chevy Volt Article · 43 comments

Josie Garthwaite says:
As a new generation of plug-in vehicles rolls off the assembly line, a new cadre of consumers has entered the market...

Mitsubishi Unveils PX-MiEV II Plug-in Hybrid Crossover SUV

Mitsubishi PX-MiEV Article · 9 comments

Eric Loveday says:
Mitsubishi will officially unveil its near-production-ready plug-in hybrid PX-MiEV II crossover at this month's 2011...

Projected EPA Range Ratings Emerge for All Versions of Tesla Model S

Tesla Model S Article · 6 comments

Eric Loveday says:
Accounting for all three variations in battery capacity, Motor Trend claims the 2012 Tesla Model S will likely earn an...

Comparing Early Criticism of Toyota Prius and Chevy Volt

Chevy Volt Article · 20 comments

Eric Loveday says:
How's the Chevrolet Volt similar to the original Toyota Prius that debuted in the US back in 2000? A dozen years ago,...