Say, during an outage during freezing temps, the batteries would be used.. then, would the act of discharging the batteries cause them to warm up enough such that solar/genset could charge them w/o damage?
I'm only remarking on this as an *emergency* procedure, not something you would do on a normal basis. Use other methods to keep your LFP warm if you can.
If you had to do a rapid turnaround during a snap freeze, and had *no other choice*, you could try to lessen the damage by hitting them up with a few heavy discharges, with pauses in between, before trying to recharge.
Now please don't laugh. The Motorcycle LFP starter guys use this "cold start technique" to get going by putting a heavy load to warm up the battery. Thing is, scaled up to our system sizes, would you ever get a heavy enough discharge to warm up? They'll turn on headlights for a little while, turn them off and wait, repeat, and then try to start. The wait period is important not only to allow the starter to cool, but also to allow the cells heat spread out a little bit.
The guy was trying to be helpful, and of course is not our application. He's using an LFP batt, although never specifically mentions it - just a generic "lithium" battery, but LFP is what's there. I thank him for trying to be helpful to members of his community.
So please don't take this as some sort of universal magical solution. It is just an idea to perhaps lessen the damage you would do if you were forced to charge during an emergency in an attempt to get your bank a little warmer lessening (not totally removing) the damage.
If we want to analyze further, after the bike starts, it is recharging at a low temp, but hopefully internally it has warmed up a little to not be quite as damaging. Again - emergency last-ditch effort to possibly save just a little bit of damage - not an operational standard operating procedure.
I was super-hesitant to even post this, because NOBODY should think this is the magic-bullet for our application. It is NOT.