Why Batteries Fail

When a lead-acid battery is discharged, a soft lead sulfate material forms on the battery plates. During the battery’s recharge, this material is lifted off the plates and recombined into the battery’s electrolyte solution.

If, however, the battery is left in a partial state of discharge for as short as 3 days, the lead sulfate material will begin to harden and crystallize, forming a permanent insulating barrier.

As this barrier becomes thicker and thicker, the battery’s ability to accept a charge or deliver energy is diminished, resulting in the perception that the battery is no longer usable.

The accumulation of such deposits, otherwise known as sulfation, is the most destructive process in the life of any lead-acid battery.

Image source: en.wikipedia.org

Common Causes of failure

Loss of electrolyte due to heat or overcharging
Lead sulfation in storage
Undercharging
Old age (positive plate shedding or “sludging”
Excessive vibration
Freezing or high temperatures
Using tap water which causes calcium sulfation
Positive grid corrosion or growth due to high temperatures
Fas recharging at rates greater than c/10