Constant output mini plug-in charger. Plug it in to a nearby socket and fix the crocodile clips to your car battery to trickle charge it constantly whilst not in use. Uses very little power - 500mA. Because classics are only used occasionally, the lead acid batteries suffer internal corrosion whilst..
OK, so most of us can tell if the garage is too cold to work but it’s useful to know the ACTUAL temperature sometimes. Enamels don’t dry properly if its too cold and you end up with a tacky surface that can take weeks to go off for example. Aerosol primers can go tack dry on the surface ..