Safe storage temp for LiFePo4 batteries

[OffgridMatty]

I have two EG4 24v LiFePo4 batteries at my cabin with the breakers in the off position. I just saw that the temperature is due to go down to -25 this weekend. Should I be concerned about them being damaged or are these fine at this temp as long as they are not in use. Temperatures this low are not common even in the winter at the cabins location. Although being 3 hours away, I'm not going to get there to move them either way. Thanks for the information!

 

[photomankc]

There is probably a lower bounds where the physical contraction might be more than desired but so far as I know the limitation is generally on charging them while at those temps. They will store fine and cold weather slows calendar aging but you probably want to avoid charging them right away when you get there. If they actually get that cold it will take a good long time for them to warm up, even under use.

It's generally recommended to get them to around 75 to 80% SOC for a long term storage period in the cold.

 

[OffgridMatty]

Thanks for the insight. I have left them at about 70% charged last time I was there. I'm planning a visit in mid February and will charge them up with my generator at that point once they are warmed up from the wood stove.

 

[Bluedog225]

Warmed all the way to the core may take a while. Not sure how you will be able to know. I believe charging frozen centers would cause damage.

 

[photomankc]

I have a rack mount system and one thing I added was a 100W chicken coup heater below the batteries. When I come in and start up the system I turn on that heater. Let it run throughout the day while I use the system. By the time I'm ready to charge in the late afternoon I have no doubt the system is warmed up. The BMS includes cold charging protection as well so that's about the best I can do. Generally in my latitude its only about 15 to 20 days were average daily temp falls below freezing anyway. Mostly its just the overnight lows and an occasional 3 to 5 days of extremely cold daytime temps for 6 weeks either side of that.

Find out if you have cold-charging protection on your battery. That at least adds some piece of mind that you wont trash them by charging too soon, just waste a little gas or sunshine.

 

[OffgridMatty]

My batteries do have temp protection in the BMS. The odd thing is that it disconnections the charge terminal at 24F and not 32F. Not sure why.

 

[photomankc]

That seems rather low to me!