Battery Charger Voltage
By Don Casey
Revised by BoatUS editors in April 2012
Because 12-volt gel batteries cannot tolerate a charge voltage above around 14.1 volts, multi-stage chargers generally limit charging voltage to that level. This makes the charger safe for gel batteries but slower to charge wet-cell batteries. Weekend boaters won't notice the difference, but for those needing to recharge only wet-cell batteries in the shortest time possible, battery chargers with a higher output voltage--typically around 14.4 volts--are available.
When the battery reaches full charge, multi-stage chargers switch to a lower voltage. The intent is to maintain the charge without gassing the electrolyte. Chargers are not perfect at this, however, and you should frequently check the water level in the batteries. If the boat will be unattended for more than a week, a simple precaution is to plug the charger into a lamp timer to limit its operation to an hour or two per day.