Traction battery temperature, sweet spot for maximum power and minimum wear

[Jerther]

Hi!!

It is my understanding that lithium batteries get damaged over time for various reasons when excessive current is applied, and that it gets worst when it is very cold, and when also it is very hot. For this reason, the car limits the power to the motor and charging current when the traction battery temperature gets too high. It limits regen braking when it's very cold, and I'm not sure it does when it's hot.

Now I've been wondering about this for a while: I don't think it limits power to the motor when it's very cold. And that worries me as I do a lot of highway at 100-110 km/h on very cold days, like down to -20 C. Also, Nissan's own battery health report contains a message about avoiding high power usage.

What are your thoughts about this? Is there a sweet spot or a sweet range of battery pack temperature (readable by leaf spy) where I can put the pedal to the metal without wearing the battery cells? My guess from reading here for a year would be anything between 5 C and 25 C?

 

[cornbinder89]

My experience with my 2015 is:
when the battery temp is below 5 bar, (2 above the "blue), in other words 1,2,3,or4 bar the regen is limited unless and until the battery warms, it is also limited when the SOC is high

Once the battery is warmer, 5 bar or more you get full regen, if the SOC isn't 85-90%
Never had my battery temp much above 6 bar so can't comment on that.
My view is that it is a car, and while I will not abuse it, I will drive as a normal vehicle and expect the battery to cope.
I expected some reduction in power on my ICE vehicle in the extreme cold and don't freak out when I see the same in my EV.
High current draw is going to be harder on it than low, just as mashing the go pedal is on an ICE car.
If your looking for the perfect condition that will make your battery last a lifetime, and veering a little either way will kill it, I think you are looking for a unicorn.

 

[Jerther]

I like unicorns! I'm looking for theoretical parameters or some ballpark for optimal longevity, so I can make decisions based on these rather than feeling or "common sens".

For example:

The best charging temperature for lithium-ion batteries is between 5°C to 45°C (41°F to 113°F) and between 10°C and 30°C (50°F and 86°F) for best performance and low aging.

Source
That's for charging. I'm looking for something like this, but for discharging. Bonus points for graphs

 

[Paul Eden]

For NMC, 25c is best fir charging and discharging

 

[Jerther]

For NMC, 25c is best fir charging and discharging

Thanks! Can you share some reference?

Meanwhile I found this short article about Nissan technology, which does not talk about temperature but is still interesting.

 

[Paul Eden]

I can't get at them at the moment. I read that the optimal temperature for NMC was between 20 and 30 so I sort of worked it out from that.