In an effort to make my van more reliable in cold climates I'm considering adding a battery heater. I have 2 Renogy LFP 100Ah batteries under the drivers seat. I often leave my van for several weeks and the interior of the van drops below 32 deg F which activates the battery's BMS system and locks them out from charging. Im thinking about adding a small heater below them to keep them warm enough to charge. Here is what I ordered https://smile.amazon.com/gp/product/B077VLB1KK/ref=ppx_yo_dt_b_asin_image_o03_s00?ie=UTF8&psc=1. The plan would be to place this under the two batteries maybe with an aluminum plate above it to distribute heat and insulate the sides and top. I would power it off the batteries themselves and while parked I would make sure it was plugged into shore power or I may be able to just power it off the solar system as long as they don't get covered in snow. Has anyone attempted this? I do have the new style Espar gas heater that would also work but would eventually run out of gas. It uses about a gallon a day of fuel when it is really cold out. The van is insulated with wool on the walls and 2" polyiso under 3/4" plywood on the floor.