We have 2 huge deep cycles in the boat. No matter how hard we use them that day, we'll put the automatic onboard charger on 2 amps and walk away. Sometimes it takes 3 hours, sometimes 8 hours to fully charge, but its very easy on the batteries.

air1lch is right about the voltage levels, a constant amp charger is much better than a constant voltage charger. A constant voltage charger will overcharge at first and undercharge later.


Regardless of how you accomplish it, two of the keys to getting good service and a long life out of your batteries is keeping them fully charged and protected against temperature extremes as much as possible.