Heated Battery Box - LiFePO4

[pgk23]

I have a unique usage, powering remote monitoring equipment in Canada. I've recently switched to using LiFePO4 batteries, which have been excellent so far; however, the winter is around the corner I need a solution for the cold weather.

I use a 150W solar panel and 2x 100 Ah LiFePO4 batteries. The batteries and charge controller stay in a locked box. The batteries do not have low-temperature protection, so I need to heat the batteries throughout the winter (keep them above 0C), but I also need a low-temperature disconnect for charging, in case the batteries ever go dead, the heat pad won't turn on and the charge controller will continue charging the batteries.

I've searched for a charge controller designed for this but haven't found anything with a low-temperature disconnect for charging. I've set up this "Inkbird Temperature Controller ITC-1000F 12V Digital Thermostat Heating Cooling Dual Relays Sensor" in between my charge controller and batteries and attached the temperature sensor to the side of one battery. When the temperature drops below 5 degrees C, the switch will prevent charging from the charge controller. I could use a heat pad connected to the heating relay but I'm using this instead "Facon 7 1/4"x25" RV Water Holding Tank Heater Pad, 12Volts DC Steps Heater Pad, for RV Motorhome Camper Trailer Boat with Automatic Thermostat Control, Up to 50 Gallons Tank" which will turn on at 45 F (7C) and off at 68 F (20C).

My biggest concern is when the relay switch is open and power from the positive wire from the charge controller just ends at the relay, the ground is still connected to the batteries, but could this fry my charge controller or the temperature relay switch?

Any ideas would be greatly appreciated. Thanks!

[Rade]

How big of an area are you heating? When we were in the design stage for our system, we were going to mount the batteries in an unheated garage that has routinely dropped down below freezing over the past winter (new garage). The system architect was kicking around the idea of a battery closet about double the size of the battery case, with fire protection and exterior ventilation and a small heater. It would have cut down on having to seal and heat the entire garage. Perhaps a small enclosure would make keeping the battery temps safe...?

We ultimately opted to put the batteries in our utility basement near the service panel and fail-over switch.

[bcroe]

I have a unique usage, powering remote monitoring equipment in Canada. I've recently switched to using LiFePO4 batteries, which have been excellent so far; however, the winter is around the corner I need a solution for the cold weather.

You might locate the batteries about 4 feet underground (with well insulated
access) where it is always above freezing. Bruce Roe

[Rade]

You might locate the batteries about 4 feet underground (with well insulated
access) where it is always above freezing. Bruce Roe

Ah! Below the frost line! ...at least in New England...

[Jamessmith.0901]

It's important to ensure that the components you're using are compatible with one another and won't cause any damage. Additionally, it's worth considering investing in a high-quality charge controller that is specifically designed for use in cold weather conditions.

[pgk23]

It's important to ensure that the components you're using are compatible with one another and won't cause any damage. Additionally, it's worth considering investing in a high-quality charge controller that is specifically designed for use in cold weather conditions.

Do you know of any models that are designed for cold weather conditions? I wasn't able to find any searching online.

[pgk23]

You might locate the batteries about 4 feet underground (with well insulated
access) where it is always above freezing. Bruce Roe

Unfortunately, these setups are more temporary, typically installed for a few months to a year, and typically on asphalt in public spaces, or within construction sites.

[bcroe]

I would just switch to a battery with lower temp operating range
for winter, any kind of heating is a tough job for small solar. Have
you tried calculating the energy heating would require?
Bruce Roe

[Jamessmith.0901]

Do you know of any models that are designed for cold weather conditions? I wasn't able to find any searching online.

Hey, yeah there are definitely some charge controllers out there that can handle the cold. Check out the Morningstar ProStar MPPT, Outback FlexMax, and the Specialty Concepts Freeze-Stat. Just do some research and read some reviews to see which one fits your needs and climate the best.

[scheek]

I am trying to use a HEATIT ET-21 Freeze Thermostatically Controlled Outlet On at 38F /Off at 50F from Amazon. I built a 2x4 framework over the batteries and use a 75w light built to heat the area. I covered the frame work with a tarp from Tractor Supply. I have a 600ah battery bank Li, which takes up abut a 3 x 5 area. Unfortunately, on consecutively cloudy days my Low Battery shut off kicks in and I'm unable to heat. My cabin is totally off grid. I'm now going to try to set my my backup generator to automatically come about an hour or two in the mid mornings to boost the batteries over the hump. Otherwise, I might have to go to a small propane heater. My control/battery room is separate from my cabin and is enclosed, but drafty. Hope, this may help, but I'm not there yet myself. Good luck! Feedback appreciated.

[azdave]

...I covered the frame work with a tarp from Tractor Supply...

A tarp is a really bad insulator. Can you find some used 1" foam board to make a better cover? 1" of foam will conserve about 80% of the heat compared to a thin tarp.

[scheek]

Thanks. Good idea. I can probably find some.