Most vehicle batteries need to be replaced three or four times during their lifetime. Average battery life is about four years, and less in hot climates. For maximum life, batteries must be fully charged and not left discharged for long.

Common premature battery failure is caused by chronic undercharging. Sulfate forms on the cell plates. This ages the plates causing permanent storage capacity loss. A good charging system is important. Vibration can also kill a battery, causing cracks in the cell connectors and separators. Excessive temperatures, evaporation or overcharging causes loss of water from the electrolyte and can damage battery cell plates.

When charging batteries, water loss and gassing can cause premature aging. Maintenance-free batteries suffer less than lead-acid car batteries, but most have sealed tops making it impossible to check the water level. Even when the case is translucent, there is no way to add water. Prying open the top can void the warranty.

Batteries with removable caps and classified as maintenance-accessible, can have water added to individual cells. Use clean distilled water only. (ordinary tap water contains dissolved salts and minerals that will contaminate the electrolyte).

Acid should NEVER be added to a battery unless it is a dry-charge motorcycle battery that requires it to activate the cells.

Some batteries do not have free liquid electrolyte inside. Absorbed Glass Mat (AGM) batteries hold the electrolyte in sponge-like fiberglass mats sandwiched between the positive and negative cell plates. This almost eliminates evaporation and gassing and the risk of spillage. The AGM design also makes a battery more resistant to vibration. Some have a spiral wound cell construction rather than rectangular cell plates to increase the surface area and storage capacity.

AGM batteries are often used in high-load applications where electrical demands are increased. AGM batteries typically have less internal resistance and heat buildup when charging or discharging. They hold their charge better than a wet cell battery, losing only about 1% to 3% of their charge/month when not being used.

Experts advise replacing AGM batteries with another AGM battery when needed. Conventional batteries may not handle the same loads as well which may cause premature failure.

AGM batteries have special charging requirements. The charging voltage should not exceed 14.8 volts even for short periods of time. They can handle very high charging currents as long as the voltage is kept within safe limits. Many newer smart battery chargers accommodate this. Slow charging at a reduced amp rate is usually best for all types of batteries.

If a battery won’t accept or hold a charge or tests bad, it needs replacement. There is no way to rejuvenate an old sulfated battery or one that has internal shorts, opens or cell damage.

The condition of a battery can be checked with a conductance tester or load tester. For accurate test results, it should be fully charged and must be tested at the recommended load (usually half its CCA amp rating).

A replacement battery must be the same group size (dimensions and post configuration) as the original, the same type (or better) than the original, and the same or higher Cold Cranking Amp (CCA) rating as the original. Most V6 and V8 engines require 600 CCA for reliable cold weather starting. Many diesel pickup trucks have a dual battery setup for added cranking power. If one battery fails, replace both batteries at the same time.

A new battery should be fully charged before it is installed, and battery cables and/or engine ground straps should be replaced so the new battery can maintain it’s charge.