Does Overcharging damage automotive batteries

After an automotive battery is used for electromotive use - in other words any use that discharges the four wheeler battery or a two wheeler battery without any charging system or insufficient charging system, it is best to charge the battery to full charge right away.

Deep discharging any lead-acid, gel, or AGM type batteries will reduce the number of cycles it can have over its life. Use of manual battery chargers is ok if the battery is not left on charge too long causing an overcharging situation. Automatic battery chargers are best in that they will not damage the battery due to overcharging if left on the charger for a few days. Automatic battery chargers that have a complete cutoff feature are the safest automotive battery chargers to use. They generally can be left on the battery indefinitely. However, do not leave a battery on an automatic battery charger for more than a few days.

Overcharging produces rapid deterioration and corrosion which shortens automotive battery life. A battery needing to be topped up continually with water is a sure sign that the car's electrical system requires careful checking. This may also affect a maintenance free four wheeler battery or a two wheeler battery. Overcharging tends to convert water in the electrolyte into hydrogen and oxygen gas, leaving the sulfuric acid behind. The result is a charged battery with excessively strong acid solution, which may be too low in quantity to fully cover and submerge all plates of all cells. Cells exposed to air do not last long! If you can see the liquid levels of the cells, and figure a way to add distilled water to each cell, so every cell is properly filled, (see an identical new battery) you may reduce the effects of this damage, otherwise, be prepared to replace it soon! (Excessive quantities of plate material often break loose with heavy overcharge, accumulating at the cell bottom, where this stuff eventually shorts out the cell.)

Mandatory battery maintenance tips:

Keep batteries clean and dry.
Dirt on a battery's surface leads to discharge and corrosion. Avoid spilling oil or grease onto the top of the battery. To remove dirt or moisture, wash with a solution of bicarbonate of soda and water. Rinse afterwards with clean water. Ensure vent plugs are in place at all times.

Keep batteries topped up

Maintaining a sufficient electrolyte level ensures the electrolyte is neither too high nor too low. Use distilled or de-ionized water and never over fill. Maintenance free batteries will usually not require topping up. Low maintenance batteries require the addition of water only once or twice per year depending on conditions.

Check electrical connections

Make sure battery terminals and cable connections are clean and tight. The application of a thin layer of petroleum jelly can help reduce corrosion.