ya know anything about "ohms" law or electronics ?
if ya do i can show ya on paper how it would work

as far as the location it would sit under the battery=because=heat rises
==== insulating battery to trap heat from resistor ====could be achived with a marine battery box and insulation that could be buried and locked underground

have you ever felt the heat from a car amp? thats why they have heat dissipation fins like a motorcycle engine =they get hot

ps a battery will not take a charge until its warm so when you start your car after being out side in subzero cold you are doing it no favors by turning off your lights, heater blower or anything else electrical AFTER it starts

THE OPPOSITE is true turn ON your lights AFTER your car is running =turn on everything= this causes electrons to cycle thru the battery and back which warms the battery and allows it to take a charge