In this video, I perform an informal, unscientific test of the Safari UT1300 lithium batteries cold-weather performance. Charge/discharge tests, how low can you go?
I put the battery inside a plastic file box to simulate a battery box and load it into my deep freeze. I then and test the charge and discharging amperage at low temperatures, all the way down to -5F. The conclusion is that though the low temp charging and discharging specs are 32F and -4F respectively, the real-world operation is much lower.
I theorize that this is due to the fact the battery itself creates some of its own heat while running. I'm pretty sure the internal BMS (Battery Monitor System) circuit board and maybe the lithium cells themselves are creating some warmth.
Your test confirms what I have found using a lithium battery for about the last 2-1/2 years. They do tend to keep themselves somewhat warm. Even when we got down into freezing temps overnight the cases of the battery never got close to freezing temperatures. Granted we were only in the high 20's and it warmed above freezing during the day. We were using an electric mattress pad (for us, not the batteries) and I think that steady drain albeit minimal helped keep the battery active and the internal resistance of the discharge created some heat. I think the general mass and weight of the battery acts as heat sync and it just takes a while for the internals to succumb to external temperatures.
In any case, cool test and positive results for the Lion battery having a functional low temperature disconnect. I have seen some tests on another YouTube channel where the LVDC on some lesser brand batteries didn't function at all.
Being avid winter campers in a winterized rig, this is one reason I will never go lithium. I know my AGMs can handle the cold and heat. The system is built big enough to handle my needs (540AH) and it’s dependable. Since I rely on solar and DC to DC to charge my batteries, the loss of power and the inability to recharge the batteries on a really cold Yellowstone day would be a deal breaker, thus the good old fashioned lead acid batteries are staying put.