Justin is right, only a defective maintainer/float charger will boil water out.
If you have a digital voltmeter, its really simple,...a float charger like the BattTender, Batt Minder, Schumacher etc are 2 stage chargers,...they will charge at 13.8 to 14.5 on the first stage (red or yellow light mode, then they will drop to float mode (green light) and you should never see more than 13.4-13.5 volts. They will not boil any water at 13.5 volts, ....except in very hot weather, 13.2 is better. If you are unsure, check the voltage. Its the voltage that boils water not amperage.
You are probably talking about an old trickle charger, which charges at 13.8-14.2 volts, and does not drop in voltage. And even at less than 1 amp they will boil water out bigtime once the battery gets fully charged.
justin_o_guy2 wrote on 03/10/10 at 15:16:21:If your float charger boiled it, your float charger isnt working right.