I am trying to get ready for winter.
Temperatures have been dropping the last two weeks, and I can already feel that my batteries don't like it.
Today, at the EV Build Day, I built an under-battery warmer.
This consists of electric heat tape - which is used for keeping pipes from freezing, or snow turning to ice on the edge of your roof - stuck into some carved-down foam insulation.
I measured my back seat battery box, and cut a piece of 1" thick foam to 35.5" inches long and 15" wide.
Then I used a router to cut a groove 1/2" deep, back and forth, in the foam to make a serpentine path for the heat tape, and pushed that in.
This insulated heating mat will go under my rear batteries. The batteries will sit directly on the foam, and more foam insulation will go around the sides of the batteries.
When I wired up the "gas plug" in the car, I wired the other end, inside the spare tire well, with a standard electric outlet box. That way, one cable going to the gas cap charging plug can run the main charger, 12V charger, battery heaters, or anything else AC I need to run in the car.
Now the next step is to take out all the batteries to put the heating mat in, and then the batteries back on top of it!