• Slow engine cranking.


Other than the obvious misuse of batteries, here are a few other types of abuse:

  • Fitting the incorrect size battery to a vehicle – don’t try to save money by fitting a smaller capacity battery – refer to the original equipment manufacturers specifications.
  • The use of additives to extend battery life is wrong – they do not have any long term benefits.
  • Installing additional equipment to vehicles such as spotlights, winches, two way radios, amplifiers and the like will cause excessive power drain from the battery. Ask your nearest Battery Clinic for advice on upgrading the battery capacity – and make sure that the “bigger” battery will fit into the tray provided in the motor vehicle.


  • Undercharging and overcharging, caused by faulty voltage regulators, permanently damage the battery and leads to reduced life.
  • One third of alleged battery faults are simply flat batteries caused by vehicle undercharging or leaving lights on. Breakdown surveys by the Automobile Association consistently indicate that drivers leaving electrical accessories on, charging system faults and poor battery maintenance are the major causes of battery problems.
  • Car batteries fatigue as they are discharged. Gradually the battery’s capacity decreases until it ceases to function satisfactorily.
  • Lead grids and electrical connections corrode over time and wear away until the electrical circuit through one of the cells breaks, causing battery failure.
  • Vibration causes damage to the battery plates which reduces battery life. Make sure your battery hold downs are tight.


  • When it is least expected! Currently there is no precise way to determine exactly when a battery will fail, therefore periodic battery checks help give warning of impending failure. Call on your local Battery Clinic for a free check.
  • Changed driving patterns. A battery check before holidays or a long trip is a good idea. If the battery is old, consider replacing it as a precaution.
  • Cold weather slows down the chemical reactions that generate electricity. An old battery will have more trouble starting the car in cold weather. Increased use of headlights, heaters, demisters, windscreen wipers and so on add to the load on a battery and reduce the amount of charge available from the alternator.
  • Hot weather. Modern vehicles with small grille areas have high under bonnet temperatures. A hot day may trigger failure in an old battery, particularly if the air conditioner has been on continually and a lot of short trips have been made during the day.


A dirty battery tends to hold spilt electrolyte on the external surface, providing a conductor for electrical current which leaks to earth, discharges the battery and causes the terminal clamp and nearby metalwork to corrode. Therefore, it is essential to keep the outside surfaces of a battery free from contamination.

Corrosion will cause a high resistance at connections and although corrosion between terminal posts and clamps may still allow sufficient current to pass to light lamps etc., it may not start the engine. In overcoming this problem clean connecting surfaces lightly with a fine abrasive and smear them with petroleum jelly before fitting.


The electrolyte level in the battery is very important. If too high, expansion due to increases in temperature and the collection of gas bubbles on the plates during charging may cause overflowing.

Spilt electrolyte provides a conduction path to earth and may allow the battery to discharge resulting in a flat battery. Spilt electrolyte may be removed with large quantities of water or by the use of a weak alkaline solution such as washing soda. (Dissolve 100g in 1 litre of water).

If the electrolyte level is too low the plates are exposed to the air and permanent damage and loss of capacity may result. Vent caps should remain in position during charging to minimise the spray of electrolyte caused by gassing.

The level of electrolyte should be maintained as follows:

Water only is lost from a battery during normal service therefore topping up should be carried out using approved battery water. The use of water other than approved battery water may lead to contamination of electrolyte. This contamination would be cumulative resulting in permanent damage to the battery.

Electrolyte should be maintained at 10 mm above plates unless otherwise specified on the battery. Acid should not be added to a battery unless some acid has been spilt or lost. Should it be necessary to add acid ensure that the specific gravity matches each cell to which it is added.

A battery that has become contaminated should be thoroughly flushed out with approved water, refilled with electrolyte, fully charged and then the specific gravity adjusted in each cell.


In the normal operation of a battery the plates are converted to lead sulphate each time it is discharged. The sulphate takes the form of fine crystals which are easily and completely dissipated on recharging.

However, should the plates be allowed to remain in the sulphated condition for a long period, the “temporary sulphate” may be converted to “permanent sulphate” and become impossible to remove. The formation of permanent sulphate is accompanied by the growth of large crystals leading to uneven expansion of the plates and eventual buckling.

Short circuits may result if the buckling causes wear and penetration of the separators.

“Permanent” Sulphation is caused by: Operating a battery in a low state of charge for lengthy periods. Allowing a battery to stand in a discharged state for a long period. Leaving a charged battery for long periods without regular recharges.

Possible Remedy: A sulphated battery may recover by charging at 1 amp for seven days or until specific gravities of the electrolyte have reached maximum and constant values. This state, then indicates the limit of recovery.


No benefit will be derived from the use of additives of dopes which neither prevent nor cure sulphation.

Insufficient charging will cause permanent sulphation because the temporary sulphate is not completely removed from the plates during recharging allowing the remainder to convert to permanent sulphate. (See Sulphation).


A battery left idle in a discharged state for a lengthy period encourages the formation of permanent sulphate and accompanying damage to the plates.

If a battery is to be taken out of service and left idle, the electrolyte must be maintained at the correct level and it should be fully charged at a low rate once a month.


If the specific gravity of the electrolyte exceeds 1.260 for automotive batteries used in temperate or tropical climates, it will result in increased chemical reaction causing deterioration of the plates and separators and shortening the life of the battery.


Overcharging is charging beyond the time necessary to fully charge the battery or conducted at an excessive rate in amps for the particular battery. It produces erosion and corrosion of the positive material and causes the grids to fracture reducing their ability to carry the starting current.

Overcharging is usually accompanied by heavy gassing which will accelerate the shedding of the active material from the positive plates. Excessive deposition of active material in the bottom of the battery container will cause a build up of silt which may bridge the plates and cause internal short circuits.

Overcharging is usually accompanied by high electrolyte temperatures resulting in rapid deterioration of the plates and separators. Overcharging may cause buckling of the plates leading to perforation of the separators and internal short circuits.