Does overcharging cause damage?zs
Overcharging occurs when the total capacity removed has been replaced by recharging and the battery remains on charge. This overcharging creates excessive heat that can cause the battery plates within the cells to buckle and shed their active material. The battery will react to the overcharge by producing an excessive amount of hydrogen and oxygen. These gases are the result of the breakdown of the water molecules within the electrolyte. The water that has been displaced by overcharging can be replaced in a serviceable (non-sealed) battery, but, in the maintenance-free sealed batteries, permanent capacity loss will result.
Excessive battery discharging can cause damage to a battery. The amount of discharge a battery can have without damage depends upon its chemistry. In general, a lead acid battery will not tolerate as deep a discharge as a NiCad or NiMh battery. Sealed lead acid batteries function best if they are discharged to only about 85% of nominal voltage (10.2V on 12V battery).