well I have a 8 volt battery in my 47 ,and it works really well for starting the motor,if I turn my heater on would it be to much voltage going ,and burn it up?And should I pull the battery out during the winter and put it in a warm place ,I live in michigan ,so the truck sits for three or four months during the snow.I found a place that sells battery tenders for 8 volt if anyone is interested!!