OVERDISCHARGING is a problem whichoriginates from insufficient battery capacity causing the batteries to beoverworked. Discharges deeper than 50% (in reality well below 12.0 Volts or1.200 Specific Gravity) significantly shorten the Cycle Life of a batterywithout increasing the usable depth of cycle. Infrequent or inadequaterecharging can also cause over discharging symptoms called SULFATION. Despitethat charging equipment is regulating back properly, over discharging symptomsare displayed as loss of battery capacity and lower than normal specificgravity. Sulfate occurs when sulfur from the electrolyte combines with the leadon the plates and forms lead-sulfate. Once this condition becomes occurs,marine battery chargers will not remove the hardened sulfate. Sulfate canusually be removed by a proper desulfation or equalization charge with externalmanual battery chargers. To accomplish this task, the flooded plate batteriesmust be charged at 6 to 10 amps. at 2.4 to 2.5 volts per cell until all cellsare gassing freely and their specific gravity returns to their full chargeconcentration. Sealed AGM batteries should be brought to 2.35 volts per celland then discharged to 1.75 volts per cell and then this process must berepeated until the capacity returns to the battery. Gel batteries may notrecover. In most cases, the battery may be returned to complete its servicelife.
CHARGING Alternators and float batterychargers including regulated photo voltaic chargers have automatic controlswhich taper the charge rate as the batteries come up in charge. It should benoted that a decrease to a few amperes while charging does not mean that thebatteries have been fully charged. Batterychargers are of three types. There is the manual type, the trickle type, andthe automatic switcher type.