Tis the season in the Northeast, I needed to do some winter-proofing of my batteries before it became a problem. Used these heater padshttps://a.co/d/h0Vlwjn. I have all 4 pads on a 12volt, 20amp switch. So I’ll only turn the switch on to run the heater pads only when Winter camping. Also, my batteries have BMS that protects them from charging if they’re too cold. Added the 16 guage steel plate so I don’t melt the battery box plastic.
I’ll remove the 1" thick, pink foamboard in the Spring, except for under the batteries, I don’t want to have to undo all the connections again. The heating pads will stay taped on year round too. Finally, I may add some strategic velcro to the outside of the battery box so I can add a blanket and keep it in place, if necessary.
The heating pads’ thermostat is for water tanks (turn on around 45F, off at 68F), but I wired a switch to easily shut the heating pads off entirely, and I have a Victron temperature sensor to monitor what’s going on in the battery box too.
This cost me <$100, and the battle born battery heaters are $200 each. I had leftover electrical parts, just had to get these switches, https://a.co/d/i9hTthT Not shown in the photos, there’s an inline fuse you have to wire in to. Don’t skip that if you try this.