I recently installed 28kw of lithium batteries in a bus conversion and we'll hit colder temperatures in central MN USA.
It is my understanding that it's no so much that lithium can not be absolutely charged below freezing but that it must be derated or compensated below 45f or so. This is because the negative ions stack up and can damage the cells of charged too quickly.
I have an idea... what if we set a temp compensation value intended for lead acid batteries was reversed? Example, I think a traditional value would be -36mV/C, but what if that value was reversed to be +36mV/C or higher. Wouldn't this invert the voltage compensation curve to produce a higher voltage as it got warmer and a lower voltage as it gets colder?
I'm just looking for a way to gradually derate the charge curve instead of a hard off or on switch. I'm also aware of a super secret "Low temperature charge current" setting HEX-Protocol in VE Direct. Would be nice to see that exposed behind a password or something.