Overcharging is the biggest killer of batteries. Excessive current produces heat which expands and breaks the grid causing the internal plates to short with each other and the active material to fall off from the plate resulting in premature battery failure. Heat from overcharging also caused evaporation of water in the electrolyte causing the cell to prematurely dry up.
The second major problem is undercharging. Batteries left unused and discharged for extended periods will cause plates to harden and sulphate. Regular short trips (stop/start situation) will also create the same problem because more power is taken from the battery than is being put in.
A battery not held properly in its cradle will vibrate and jump while the vehicle is moving, causing the active material on the plate to fall off resulting in loss of power and battery failure.
Corrosion between battery post and cable also puts strain on the battery. This corrosion limits the current flow to the battery during charging and severely hampers power from the battery during starting.
In cold climates, normally a battery "ages" as the active positive plate material sheds (or flakes off) due to the expansion and contraction that occurs during the discharge and recharge cycles. Brown sediment, called sludge or "mud" builds up in the bottom of the case and can short the cell out. In hot climates, additional causes of failure are positive grid growth, negative grid shrinkage, buckling of plates, or loss of water.
Another major cause of premature battery failure is lead sulphation. Using tap water to top up batteries can produce calcium sulphate that also will coat the plates and fill the pores. Recharging a sulphated battery is like trying to wash your hands with gloves on. When the active material in the plates can no longer sustain a discharge current, the battery “dies”.
Battery Preventive Maintenance
Maintain correct electrolyte level – add only distilled water to within (3 to 7 mm) below the bottom of the filler tube (vent wells or splash barrel). The plates need to be covered with electrolyte at all times. Avoid over- filling especially in hot climates, because heat causes the electrolyte to expand and overflow.
Remove corrosion from both ends of each battery cable and both terminals.
Clean the battery top.
Check the alternator belt tension.
Check battery hold-down.
The preventive maintenance frequency is dependent upon climate and battery type, but you should perform this at least once before cold weather starts and once a month in warm weather.