That's a good question Tina. All battery chargers use a rectifier. It converts AC (alternating current that reverses direction) to DC (direct current that only flows in one direction). They usually use a capacitor to smooth out the current. Our concern in cleaning is the Amp draw (how much "work" it's doing), so we don't monitor "voltage", but rather the amps.) Just thinking out loud here...could have/build a rectifier (ie: center tap transformer, throw in some diodes, capacitor to regulate current, etc.)...or...get a manual battery charger ...with an amp gauge, to monitor the "work" it's doing. Although there are several ways to accomplish this, IMO, the best way is to get a manual battery charger & be done with it. :) FWIW I use a Schumacher 225 amp manual charger, and run it at 20 amps usually.