one can make a battery charger using only a 120 v light 
bulb and a rectifier pulled from an old alternator. Put 120 vac, the light 
bulb, the diode and the battery all in series. The wattage of the light bulb 
(or other 120 v load) determines the current flow. It would help to have an 
ammeter in there somewhere I would think. I've never tried it