The Selmar Turbo 4 is a manual 12V 4-Amp charger for lead-acid batteries that requires active monitoring to prevent overcharging. Operation involves connecting the charger to the battery, plugging it into an AC outlet, and disconnecting once the ammeter needle drops to zero. Detailed instructions can be found in a Free Instruction Manuals PDF . Old Car Battery Charger - How to use it? | DIYnot Forums