Dakota Lithium battery and cold temp

[Thomas_Honesco]

I have a Dakota Lithium battery 100 AH installed in a battery compartment on a 2014 Casita Travel trailer. The last 10 days our outdoor temperature is around 35 degrees in the daytime and 20 degrees at night. I have a 100 watt solar panel through a Renogy 20 amp solar controller that I keep connected.
The system has worked great in the 2 years since I've installed it. However since the cold snap the Renogy App states that my battery is only charged to 67%.
Is this due to the cold? What would be the best protocol... disconnect the solar panel.... I have a circuit breaker on the battery should I trip the switch...
put a light bulb in the battery compartment to heat up the area? Assume that when the weather heats back up all will be back to normal.
The system is charging properly when I use AC or solar but drops back down to 67% when disconnected.
Thank you for your great videos. I follow your suggestions religiously in building my systems.

 

[Doggydogworld]

LiFePO4 battery? Cold soaking at 20F overnight almost guarantees the battery will be well under 32F when your panel and controller start charging it in the morning. Charging LiFePO4 below 32F is a no-no and can damage it.

Was the trailer heated overnight? If so the Casita battery compartment, even though vented, should stay warmer than the outside air. So your battery may have stayed above freezing, or at least not dropped all the way down to 20F.

Your battery BMS may have a low temperature cutoff to prevent damage (check specs). Maybe yours prevented charging most of the day and by the time the battery warmed up there was only a couple hours of sunlight left. Low temp cutoff is a last-ditch emergency feature, you don't want to use it in normal operation. Among other things, they tend to measure battery skin temperature. The skin can heat up much faster than the core on a sunny day.

First I'd make sure the battery core is above freezing. If you can't measure core temp directly, my best suggestion is to sit it in a warm room for 12-24 hours.

Once you know the battery is warm enough you want to make sure it stays above freezing. That's not hard in your conditions. Insulating the compartment's outside walls and floor should do the trick on 20F nights, assuming the trailer itself is heated. Use a thermometer to be sure. If the trailer is not heated, insulating the compartment on all sides plus a heating pad or maybe light bulb should work.