Cold Weather Battery Charging

[Famous_addit]

Hello,

I have two LiFe4po 2.5 kWh 12v batteries and the weather is starting to get pretty cold where I am.

The batteries do not have an internal heater and I will need to use them throughout winter. I live off grid is an old unheated stone house in the Alps so the room they are kept in is only marginally warmer than the outside temperature.

At present it is only dropping below freezing at night, when they are not charging (currently being charged by 800w of solar), however I expect it to drop below freezing during the day time some time in the next couple of weeks.

I have read that you should not charge LiFe4po batteries is their temperature is below zero centigrade. So, my question is: how can I continue to use these batteries throughout winter?

I have seen these small heating pads that people use to make mini green houses or to heat car seats. Could I just sit my batteries on one of these all winter? Any other ideas or if there is a proven solution (I can't be the first person to encounter this), I welcome your insight.

TIA
Z

 

[DThames]

Heaters, link. Controller to turn the heater off and on.

See links above. I would want to bundle the heaters, batteries, and temp sensors together and insulate the system so you would be only heating your batteries and not the Alps.

 

[DThames]

Larger heater with thermostat.

 

[Old_Skewler]

I have read that you should not charge LiFe4po batteries is their temperature is below zero centigrade. So, my question is: how can I continue to use these batteries throughout winter?

Welcome to my life! This is my first winter also running lithium batteries and I had to deal with the same problem a couple of weeks ago when we dipped below 30F where I live.

A few things you should consider:

1. Find out from your battery specs exactly the temp limitations. For instance, my batteries can discharge up to 14F and can only charge above 32F.
2. Find out whether your battery has BMS safety to prevent damage
3. Be ready to adapt under cold climate:
- performance degrades fast as batteries are operated in extreme conditions
- keep an eye on battery SOC and temperature, if your BMS gives you that info.
- reduce charging rate in the beginning of the charge and as batteries warm up, and they will with charge, then you could increase charge rate back to your goal

I personally went the old caveman style and added a kerosene heater in the shed to warm up my battery before trying to charge it. I only needed to run the heater about 30 mins to get the battery temp above 35F. After they start charging, they naturally warm up up to 50F. Incredible.

Stay warm and good luck!

 

[740GLE]

What solar charge controller are you using?

Seeing sunlight is much shorter these days, what are you seeing for daily generation? Factor that into and heating needs.

 

[740GLE]

Double post