Failure
Common battery faults include:
- Shorted cell due to failure of the separator between the positive and negative plates
- Shorted cell or cells due to build up of shed plate material below the plates of the cell
- Broken internal connections due to corrosion
- Broken plates due to vibration and corrosion
- Low electrolyte level
- Cracked or broken case
- Broken terminals
- Sulfation after prolonged disuse in a low or zero charged state
Corrosion at the battery terminals can prevent a car from starting due to electrical resistance. The white powder sometimes found around the battery terminals is usually lead sulfate which is toxic by inhalation, ingestion and skin contact. The corrosion is caused by an imperfect seal between the plastic battery case and lead battery post allowing sulfuric acid to react with the lead battery posts. The corrosion process is also expedited by over charging. Corrosion can also be caused by factors such as salt water, dirt, heat, humidity, cracks in the battery casing or loose battery terminals. Inspection, cleaning and protection with a light coating of dielectric grease are measures used to prevent corrosion of battery terminals.
Sulfation occurs when a battery is not fully charged. The longer it remains in a discharged state the harder it is to overcome sulfation. This may be overcome with slow, low-current (trickle) charging. Sulfation is the formation of large, non-conductive lead sulfate crystals on the plates; lead sulfate formation is part of each cycle, but in the discharged condition the crystals become large and block passage of current through the electrolyte.
The primary wear-out mechanism is the shedding of active material from the battery plates, which accumulates at the bottom of the cells and which may eventually short-circuit the plates.
Early automotive batteries could sometimes be repaired by dismantling and replacing damaged separators, plates, intercell connectors and other repairs. Modern battery cases do not facilitate such repairs; an internal fault generally requires replacement of the entire unit.
Read more about this topic: Automotive Battery
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