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Charging LiFePO4 Battery in cold conditions

BroomJM

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Apr 7, 2021
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If you have batteries in your house, at around 70 degrees, then take them out into an unheated garage where the temperature is near freezing, can you immediately plug them into a charger and rely on the heat generated during the charging process to keep them warm?

Maybe a better question to ask is: Is the heat generated by charging enough to keep cells above freezing, if they were warm when you started charging them?
 
If you have batteries in your house, at around 70 degrees, then take them out into an unheated garage where the temperature is near freezing, can you immediately plug them into a charger and rely on the heat generated during the charging process to keep them warm?

Maybe a better question to ask is: Is the heat generated by charging enough to keep cells above freezing, if they were warm when you started charging them?
Maybe.... it would depend on many things..... but I would not count on it.
 
This really depends on the environment, spacing, insulation around the battery, air flow, etc.
 
I turned on a small heater in the garage to ensure it doesn't get anywhere near freezing in there.
We hit 36F in the Bay Area today. I only had a peak of ~15A of charge current going into my 560Ah LiFePO4 battery so decided to just let it continue, but is there an absolute ‘do not charge LiFePO4 below this temperature’ threshold, even at exceedingly modest charge current levels (<0.03C)?
 
Why not add a low temperature disconnect just in case, I believe Victron makes one.
 
Why not add a low temperature disconnect just in case, I believe Victron makes one.
You need VIctron Equipmeant and have it setup for a virtual Network.

No. LFP charging is very efficient and generates very little waste heat.
I do not have experience charging my lithium’s on cold dats, but my Lead Acid Batteries only seem to stay 5 degrees to 10 Degrees above ambient temps when charging at around 7% ah capacity. Also seems the colder it is, the less it heats.
 
Why not add a low temperature disconnect just in case, I believe Victron makes one.
The larger batteries have a BMS with a low-temp sensor, but I have others (repurposed or unique stuff I have built myself) where they either don't have a BMS at all, or the BMS is a very small, simple unit. I will make sure nothing is getting charged when it is cold enough to be a concern, it was more a question I had about the amount of heat created during charging and whether or not that would keep cells safe. Sounds like it's not a lot of heat and not worth risking it.
 
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