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
- 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