EVs with Thermal Management System (TMS)

[RegGuheert]

If every EV has it, then what's Nissan's rationale of not including one in Leaf, any ideas?

Simply put, it greatly reduces the cost to manufacture the product. A big part of that cost reduction is allowing any Nissan EV to be manufactured alongside any other Nissan product on their assembly lines, which has huge benefits for them.

I suspect in the long term very few EVs will have or need TMS.

 

[johnqh]

This may have been covered somewhere...

But does TMS operate when the car is parked and off?

I think a optional solar-powered, always-on system which cools the batteries can be cheaper and easier to add than a full featured TMS, and greatly improve the battery life in hot climates.

 

[TonyWilliams]

As for the capacity of the battery in the cold, yes that goes down, but I think it is a very small loss. The only measurements I have for this is the Rated range shown on our Model S, which, in the winter shows a loss in rated range of only 1-3 miles.
Of course, the projected range drops by a lot more. But that is due to the increased energy it has taken to move the car through the colder/denser air, increased HVAC use (both for battery pack and cabin) and increased rolling resistance.

You're comparing a TMS car with completely different cell architecture and chemistry with the LEAF in cold weather?

Whenever I talk about range in an EV (any EV), unless I specify otherwise, I mean actual range performance... not rated range, ideal range, GOM, fuel bars, EPA, etc. Our cold weather data for the LEAF was gathered by numerous folks who actually volunteered to drive their cars in the cold after having left the car sit all night to cold soak the battery WITHOUT A HEATER !!!

I'm going to continue to go with that data. Disclosure; I reimbursed each volunteer with a high quality 100% organic cotton t-shirt with the "Love My LEAF" logo.

 

[aphysician]

Hi Tom,

Whatever the reasons were, I agree it basically rules out Leaf in those climates esp for people with longer commute. If they are going to sell EV all over the world, then they would need to fix this, either with TMS or improved battery architecture.

Hari

 

[TonyWilliams]

This may have been covered somewhere...

But does TMS operate when the car is parked and off?

I think a optional solar-powered, always-on system which cools the batteries can be cheaper and easier to add than a full featured TMS, and greatly improve the battery life in hot climates.

No, solar powered won't work, because solar will only provide the power; not the actual heating and cooling that TMS does. Plus, we are a LONG way from having enough PV solar efficiency for the small footprint of a car to provide enough power. How well does that solar powered TMS work at night, BTW?

On the Volt, I believe it will operate the TMS while unplugged above some value (50%-80% SOC). On Tesla products (including my Rav4 EV and future Mercedes B-Class EV), it doesn't appear that the TMS will work at all unless you are preconditioning the car.

 

[TonyWilliams]

Hope it changes soon, or they will hurt their reputation in these climates, which could be expensive to fix.

Too late for that!

 

[aphysician]

@WetEV

Thank you for your reply. I agree about cost and complexity esp when benefit is not sure or tiny for most people, but still a product performance should not differ this much, it is bad for reputation. It may have been right strategy for start, but now after they have established themselves as leaders, they should go after all markets. Competitors will pick up that sooner or later, already I see statements like "better cold weather performance due to liquid thermal managment system" on other EV websites. I really don't care what approach they take, but needs to have some predictable performance or enough backup not to let you stranded. Hopefully I see something from Nissan which is relevant in my climate. It will be interesting to see which of listed options gain momentum. Either way Nissan did an amazing job with Leaf, and was one of the pioneer in bringing EVs to mainstream, and it is already making difference. Wish I could enjoy it too.

 

[johnqh]

This may have been covered somewhere...

But does TMS operate when the car is parked and off?

I think a optional solar-powered, always-on system which cools the batteries can be cheaper and easier to add than a full featured TMS, and greatly improve the battery life in hot climates.

No, solar powered won't work, because solar will only provide the power; not the actual heating and cooling that TMS does. Plus, we are a LONG way from having enough PV solar efficiency for the small footprint of a car to provide enough power. How well does that solar powered TMS work at night, BTW?

On the Volt, I believe it will operate the TMS while unplugged above some value (50%-80% SOC). On Tesla products (including my Rav4 EV and future Mercedes B-Class EV), it doesn't appear that the TMS will work at all unless you are preconditioning the car.

I am talking about in hot weather. And I am not talking about full featured TMS.

Power is an issue. I am not sure how much power the current panel on SL spoiler is generating. Probably only 2w. However, imagine a sunshade (the one you put to cover the dashboard) with solar panels on it. You can probably generate 25W for it, and the panels shouldn't cost more than $200.

I think 25W should be enough to make a major difference to cool the batteries.

I don't think TMS make a lot of sense, unless it is powered when the car is off. When the car is moving, the batteries is at least air cooled. However, when parked, the solar energy can easily heat up the car and battery. It is not effective to cool the batteries for 1 hour of driving, but leave it to heat up for 8 hours of parking under the sun.

 

[aphysician]

@ RegGuheert

Valid point. Benefits to them and lower cost for consumers too. Battery research is certainly progressing rapidly, will be interesting to see how different Gen 2 EVs will be, and what technology would they use? We should get more clarity about future of TMS then.

 

[aphysician]

Hi Tony,

As usual, very clear explanations. Cold range data with Leaf was exceptional, it helps to have real world performance. As you know already, that helped me in my decision. I really thank your volunteers for doing that. If you are game, then you can generalize to all EVs. It was really very scientific way to validate data. I don't know however how would Tesla folks react on getting "LoveMyLeaf" Tshirts.

I didn't know there was difference in the way TMS works, between GM and Tesla. GM's solution seems smarter, only if they had bigger battery. Still having a TMS is like an insurance policy, the performance of it can be changed with a software update.

@johnqh brings up an interesting point. Solar powered TMS could be in future, once PV efficiency increases. I saw somewhere on Nissan owners blog, in a video interview of a Nissan executive, that to charge the EV battery, they would need a trailer of solar panel, so I don't think spoiler panel generates much electricity. However @johnqh has some interesting suggestions of integrating solar panel in a sunshade or maybe roof to generate enough power for TMS, so it doesn't drain battery power to cool/heat batteries. Anything that reduces the drain on the battery in extreme climates could be helpful.

Hari

 

[aphysician]

@johnqh

Thank you for your reply. You bring up an interesting point. Solar powered TMS could be in future, once PV efficiency increases. I saw somewhere on Nissan owners blog, in a video interview of a Nissan executive, that to charge the EV battery, they would need a trailer of solar panel, so I don't think spoiler panel generates much electricity. However you have some interesting suggestions of integrating solar panel in a sunshade or maybe roof to generate enough power for TMS, so it doesn't drain battery power to cool/heat batteries. Anything that reduces the drain on the battery in extreme climates could be helpful.

I agree TMS makes sense when they work while EV is not moving to keep optimum battery temperature in extreme climates, so it doesn't loose a lot of energy. Though it is also important how much power TMS will consume to do that. So after reviewing everyone's responses it makes sense to have TMS that works when EV is stationary, may be when it is plugged in/preconditioning, only in EVs with bigger battery as to have enough juice. It may not be useful in EVs with less than 80 miles range. It will be exciting if we can use other renewable energy source to power it to reduce battery brain.