Insulated battery box: need advice to finish

[hammick]

I haven’t built mine yet but I am thinking about using this thermostat to control a heating pad in the winter and possibly a cpu fan in the summer.

DC Thermostat

OP here. I'm using the seed heating pad listed below under a full size baking sheet in the insulated box shown above. I'll get some photos up later tonight. I'm 1,200 miles away from my batteries. My insulated garage is 31 degrees Fahrenheit currently and it's -14 outside right now with life threatning wind chills. It was - 20 first thing this morning with -44 degree wind chills. My batteries are fluctuating between 9 -11 degrees Celsius and the heating pad uses very little power. I have the pad set to 50 degree Fahrenheit. I'm very happy with it.

See heating pad

Aluminum baking sheet

 

[Honuz]

OP here. I'm using the seed heating pad listed below under a full size baking sheet in the insulated box shown above. I'll get some photos up later tonight. I'm 1,200 miles away from my batteries. My insulated garage is 31 degrees Fahrenheit currently and it's -14 outside right now with life threatning wind chills. It was - 20 first thing this morning with -44 degree wind chills. My batteries are fluctuating between 9 -11 degrees Celsius and the heating pad uses very little power. I have the pad set to 50 degree Fahrenheit. I'm very happy with it.

See heating pad

Aluminum baking sheet

I think that the optimal temp is near 20-25°C to get max lifetime of them and let them be charged at high current.

 

[hammick]

I think that the optimal temp is near 20-25°C to get max lifetime of them and let them be charged at high current.

My generator charges them at around 95 amps and they heat up close to 20 degrees C when charging (insulated box holds heat also). My solar charging in the winter is around 25 - 30 amps max. I can't turn up the heating mat until next time I'm up there.

 

[Yurtdweller]

I just installed a very similar seedling heater, before having read your report. Mine may be identical, but with a different appearance/brand name. All the specs and the price are virtually the same. It was an emergency quicky install. I simply put the pad under the pack, with a 1 inch foam pad between the heat pad and the pack, and threw a thermal blanket over the whole thing. It is working great in the Texas winter storm. I wrote my own entry/review just now. I have mine set to about 10°c to conserve power. Very satisfied with this solution.

 

[hammick]

I just installed a very similar seedling heater, before having read your report. Mine may be identical, but with a different appearance/brand name. All the specs and the price are virtually the same. It was an emergency quicky install. I simply put the pad under the pack, with a 1 inch foam pad between the heat pad and the pack, and threw a thermal blanket over the whole thing. It is working great in the Texas winter storm. I wrote my own entry/review just now. I have mine set to about 10°c to conserve power. Very satisfied with this solution.

Yeah they are great. Mine has been keeping my batteries at a consistent 9 -10 degree Celsius even when the garage dropped to 30 degrees Farenheit.

 

[BabylonFive]

It sounds like if the temp thresholds were set correctly the batteries would stay at minimum charging temp and then self-heat once charging started and no longer need the heaters until they completed charging and then began to drift back down. Insulation is then key to keeping the heat inside.

My design adds a bilge blower to the box and turns on when temp gets above a top threshold as well.

It turns out to be hard to both cool and heat a battery box! It's almost like you want controllable insulation. I hope the insulation, heater, and fan achieve this for me.