Common Automotive Battery Faults

Car broken down? Did you check under the hood? Faulty or flat batteries, not surprisingly, are one of the most common causes of breakdown. A flat vehicle battery is most commonly caused by:                                                                                                                                                                           

• lack of use or vehicle only used for short journeys
• something has been left on
• a faulty component draining the car battery
• a fault with the vehicle's charging system
• a fault with the vehicle battery itself

Short journeys or insufficient use of a vehicle shorten the total life span of a four wheeler battery. This 'under charging' results in 'sulphation' if the battery voltage is allowed to remain below 12.4 volts. Sulphation is the hardening of the lead plates within the battery and it reduces the battery's ability to accept or hold a charge.

Automotive batteries, whether they are car batteries or truck batteries can fail for other reasons too. For instance, excessive vibration, over charging, corrosion and temperature (extreme heat and cold) can make the vehicle battery fall flat.

Common battery faults include:

• Shorted cell due to failure of the separator between the positive and negative plates
• Shorted cell or cells due to buildup 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
• Sulphation after prolonged disuse in a low or zero charged state
• Frequent and continuous overcharge

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 sulphate 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 sulphuric 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.

Sulphation occurs when an automotive battery is not fully charged. The longer it remains in a discharged state the harder it is to overcome sulphation. This may be overcome with slow, low-current (trickle) charging. Sulphation is the formation of large, non-conductive lead sulphate crystals on the plates; lead sulphate 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, inter-cell connectors and other repairs. Modern battery cases do not facilitate such repairs; an internal fault generally requires replacement of the entire unit.

Battery maintenance is another topic we’ll cover at a later stage.  However, here’s a quick solution. If you do only use your car occasionally and for short journeys, please invest in an intelligent charger/battery conditioner that can be left connected for long periods without risk of damage to the battery.