BMS Temperature Goal

[Sans-gas]

I’m curious. Does anyone know what the optimum battery temp is for charging? I’ve wondered if when I’m driving and outside temps are over 90, does the BMS really heat the battery or adjust the temperature downward sometimes for maximum charge rate?

 

[Tam]

I’m curious. Does anyone know what the optimum battery temp is for charging? I’ve wondered if when I’m driving and outside temps are over 90, does the BMS really heat the battery or adjust the temperature downward sometimes for maximum charge rate?

That's the idea for BMS.

It protects the battery regardless of ambient temperature and optimizes charging speed by optimizing the internal battery temperature for charging as well.

I don't know what are the optimal internal temperature range to protect the battery and for charging.

A lithium battery can be permanently damaged if it's charged while its internal temperature is sub-freezing below 32F 0C.

 

[ZOMGVTEK]

Tesla appears to target ~50C pack temp for rapid charging. This is 122F, so it might even heat the battery when its 90 outside if its parked in a shaded area for a while. The ideal temperature is a bit complex, but I suspect one of the primary reasons why they heat it so significantly is mainly to increase charge rates. Colder batteries have higher internal resistance and wont charge as rapidly in addition to lithium plating concerns which causes long term degradation. But the rub here is higher temps also increase degradation, so its a trade off. Generally it appears more likely a component failure is going to kill the pack before degradation is a significant problem, so this might not matter that much anyways.

 

[Dexion11]

According to scan my Tesla,
Target battery active cool 131f
Target passive cool 86f
Target battery active heat 19.4F (that's not charging that's just existing)
Anywhere below 86 and above 19.4 if not charging or preconing it does nothing.

When fast charging it tops out at that 131 then turns on the ac. No pic of that but you can YouTube and watch people supercharge with scan my Tesla on.

Down near the bottom of the pic. It's a pic after I unplugged so you get the mess at the bottom.