The purpose of recharging a battery is to restore the full operational condition that the battery is designed to perform.
The recharging process restores the original chemical potential the correct and electrical capacity of the battery. Recharging is the discharging reverse process. Therefore, the more discharged the battery is the more charge is required to achieve full charge state.
Single battery with separate charger
To properly recharge one or more batteries, always follow charger manufacturer directions and safety precautions.
Optimum battery life will be obtained if a “GREEN” hydrometer condition can be maintained, and batteries should not be left in a deeply discharged state. Batteries should be recharged as soon as possible once a “WHITE” hydrometer is observed.
Once the state-of-charge has reached 100% charging should only be continued for long periods at a reduced rate (on-charge voltage of 13.5/13.8 volts) to prevent long term electrolyte loss.
Alternator voltage regulator settings should be in the order of 13.8 – 14.2 volts, the higher setting being preferred. On applications with repetitive deep cycling, a charging voltage of at least 14.8 volts is recommended until full charge is reached however the maximum charge voltage should not exceed 15.8 volts.
Chargers with charge rates up to 50 amperes are generally satisfactory. If the battery becomes hot to touch, or starts to spew electrolyte, charging should be reduced or stopped to allow the battery to cool down before continuing charging at a reduced rate.
Note: Slow charging rates are preferred to fast boost charging.