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Re: 2018 Leaf battery overheating

Posted: Fri Apr 05, 2019 8:00 am
by OrientExpress
jdcbomb wrote:What actual temp (F) is considered high and "detrimental" for the life of the 40 kWh battery. Greater than 90? Greater than 120? Assuming a 12 hr period here as it appears the battery doesn't drastically dissipate the heat once it is gained.
When the battery temp gauge gets into the red part, the LEAF will throttle back the amount of charging and power available.

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Re: 2018 Leaf battery overheating

Posted: Fri Apr 05, 2019 8:15 am
by jdcbomb
Thanks..aware of this. Just curious to understand what is a "bad" temperature (in F, not by vague bars) for the 18 MY?

And wondering if 95 F is actually within normal operating limits and won't cause significantly faster degradation than say a "comfortable" 78 F temp.

Re: 2018 Leaf battery overheating

Posted: Fri Apr 05, 2019 8:23 am
by DaveinOlyWA
jdcbomb wrote:What actual temp (F) is considered high and "detrimental" for the life of the 40 kWh battery. Greater than 90? Greater than 120? Assuming a 12 hr period here as it appears the battery doesn't drastically dissipate the heat once it is gained.
Its a sliding scale that considers SOC, time and temperature so your question is all but unanswerable. Some tidbits to consider;

The most efficient charge (that gets the most range per unit of time) is when starting charge with pack temperature in the mid to low 80's ºF.

**80% SOC is good but 70% SOC is better; recommendation is ALWAYS charge to cover your needs. ef everything else. **

Heat or heavy QC is not your main worry. Its "time" at high SOC.

Heat dissipation is almost completely dependent on the delta between the pack and the ambient. So if you live in a 24/7 hot area, I would not charge to full EVER. (see "**" above)

Re: 2018 Leaf battery overheating

Posted: Fri Apr 05, 2019 8:24 am
by WetEV
jdcbomb wrote:What actual temp (F) is considered high and "detrimental" for the life of the 40 kWh battery. Greater than 90? Greater than 120? Assuming a 12 hr period here as it appears the battery doesn't drastically dissipate the heat once it is gained.
"Detrimental" isn't really how it works.

Li ion batteries have side reactions that remove active Lithium and otherwise degrade the anodes and cathodes.

These reactions happen in any Li ion battery at any operational temperature. Like most chemical reactions, these reactions seem to follow an Arrhenius relationship, going faster at higher temperatures. A temperature higher by 10C or a bit less would double the rate of capacity loss.

So if your "normal" battery temperature is 25C, a day trip that raises that to 35C will roughly remove an extra day of battery life. A day trip that raises battery temperature to 45 C would remove roughly three extra days of battery life.

This is a crude back of envelope type calculation. A better calculation could be done by considering the warmup time and the cooling time, and using the roughly 8C best fit for the Arrhenius relationship. The results wouldn't be much different.

If you do a trip that adds 10C once a year, I doubt if you can observe the faster rate of capacity decline, even with multiple cars driven exactly the same. If you do a trip that adds 30C three times a week, different story.

Re: 2018 Leaf battery overheating

Posted: Fri Apr 05, 2019 8:36 am
by WetEV
jdcbomb wrote:Thanks..aware of this. Just curious to understand what is a "bad" temperature (in F, not by vague bars) for the 18 MY?

And wondering if 95 F is actually within normal operating limits and won't cause significantly faster degradation than say a "comfortable" 78 F temp.
That's about 10C warmer, so yes, the battery would degrade faster. At a "comfortable" 25 C (78 F) and often less, the battery would last more than three times the warranty.

http://www.nec.com/en/global/techrep/jo ... 120112.pdf

Re: 2018 Leaf battery overheating

Posted: Fri Apr 05, 2019 1:19 pm
by LeftieBiker
"Detrimental" isn't really how it works.
It's close enough. Assuming that 3% degradation per year is "normal" (we wish!) then anything that raises the rate substantially above that could be considered "detrimental." In the case of the 40kwh pack (which I am probably going to name something less than flattering) time seems to once again be a major factor, as it was with the original "Canary" pack, so heat once again has some real competition. I haven't done a LeafSpy reading since December; once it warms up I'll start doing it monthly again, and will have an annual figure for my car, for the first year, this month.

Re: 2018 Leaf battery overheating

Posted: Fri Apr 05, 2019 3:32 pm
by SageBrush
jdcbomb wrote:What actual temp (F) is considered high and "detrimental" for the life of the 40 kWh battery.
Detrimental to whom ? Nissan chooses according the warranty. If you want your battery to do better than have ~ 65% of new capacity by year 8 or so, do not follow Nissan's advice.

Re: 2018 Leaf battery overheating

Posted: Fri Apr 05, 2019 5:04 pm
by jdcbomb
Thanks for all the replies. I know the question and even the word "detrimental" is vague and subjective, but I believe my point was to see at what temperature do we believe (not Nissan necessarily) would cause the most degradation. Indeed this also requires a time frame, of which I think 12 to 24 hr minimum period would be sufficient to observe an effect versus over several days (or maybe not?).

Re: 2018 Leaf battery overheating

Posted: Fri Apr 05, 2019 7:50 pm
by WetEV
SageBrush wrote:
jdcbomb wrote:What actual temp (F) is considered high and "detrimental" for the life of the 40 kWh battery.
Detrimental to whom ? Nissan chooses according the warranty. If you want your battery to do better than have ~ 65% of new capacity by year 8 or so, do not follow Nissan's advice.
And don't live in Phoenix.

Re: 2018 Leaf battery overheating

Posted: Sat Apr 06, 2019 12:46 am
by SageBrush
jdcbomb wrote:Thanks for all the replies. I know the question and even the word "detrimental" is vague and subjective, but I believe my point was to see at what temperature do we believe (not Nissan necessarily) would cause the most degradation. Indeed this also requires a time frame, of which I think 12 to 24 hr minimum period would be sufficient to observe an effect versus over several days (or maybe not?).
A binary answer or threshold does not exist. The very approximate answer is that battery will age twice as fast for every 7 - 10C increase in temperature. This is based on Arrhenius.

Is it clear how this works then ?
As one example, 4 hours at 20C has about the same aging as one hour at 35 -40 C

A LEAF that is rapid-gating has a battery temperature of ~ 50 C. Compared to the 20 C or so that Nissan uses for its warranty based engineering designs, the battery will age 8x - 16x as fast during the affected time at 50C. To go back to your implied question in terms of a battery heating up to rapid-gate temperature, the cooling down period ~ follows Newton's law of cooling. Integrate that function and apply the temperature average to Arrhenius' law.

I apologize if this is greek to you.