General Battery Knowledge

Understanding of Lead Acid Batteries

A little bit of care and understanding of how your battery operates and is maintained will insure maximum service life.


Lead acid batteries are used as a power source for vehicles that demand a constant and uninterruptible source of energy. Just about every vehicle today does. For example, street motorcycles need lights that operate when the engine isn’t running. They get it from the battery. Accessories such as clocks and alarms are battery-driven.

Lead acid batteries are relatively simple in design. Dissimilar metal plates are immersed in an electrolyte solution consisting of sulfuric acid and water. These are then insulated from each other with a permeable, non-conductive material, which allows the transfer of ions. The transfer of ions occurs during the discharge and recharge of the battery. Also occurring is the change in specific gravity or density of the electrolyte. During the discharge period, sulfuric acid is drawn from the electrolyte into the pores of the plates. This reduces the specific gravity of the electrolyte and increases the concentration of water. During the recharge, this action is reversed and the sulfuric acid is driven from the plates, back into the electrolyte, increasing the specific gravity.

During the discharge, lead sulfate is being formed on the battery plates. Although this is the normal activity within the battery during discharge, a timely recharge is required to drive out the sulfuric acid into the electrolyte. Without this recharge, the lead sulfate will continue to develop and become difficult if not impossible to breakdown during recharge. Once this advanced sulfation develops, permanent capacity loss or total failure of the battery is likely. Besides the sulfation concerns, many other detrimental actions are taking place inside the battery while in a discharged condition.

The corrosive effect on the lead plates and connections within the battery is greatly increased due to the reduced specific gravity of the electrolyte. The corrosion of the plates will typically result in a gradual reduction in performance followed by battery failure. The corrosion associated with the inter cell connectors and the connecting welds will in many instances result in a sudden battery failure. The corroded connector may have sufficient integrity to support low drain accessories such as lights and instruments, but lack the necessary strength to provide the high discharge current required to start the vehicle. This corrosive effect can also dissolve the lead into solution, which in turn may compromise the plate insulators and result in micro shorts. Another condition that frequently occurs in a discharged battery is freezing. In a deeply discharged battery, the electrolyte has a reduced specific gravity and becomes a higher percentage of water than sulfuric acid. During this condition, the battery may freeze at temperatures as high as 32°F.The electrolyte in a fully charged battery will not freeze in temperatures down to -65°F.

Deep discharge can be created by a multitude of conditions, but the predominant reason is neglect. During long periods of storage, the battery state of charge must be checked and maintained per the battery manufacturers recommendations. Other conditions that can drain the battery are inoperative or inadequate charging systems on vehicles, parasitic or key off drains, loose or dirty terminal connections, etc. Although many of these conditions can be corrected, often the problems you cannot correct may be overcome by a periodic charging schedule. You can establish a routine by which you check and charge your battery or choose to permanently attach an automatic charger while the vehicle is not in use.

When charging your battery, always refer to the instructions on both the battery and the charger. While maintaining your battery at a full state of charge will insure optimum life, overcharging may significantly reduce it. With a conventional type battery that offers access to the cell compartments, the periodic addition of distilled water may be required. Water loss is normal in these batteries through the process of electrolysis and evaporation. Low electrolyte levels that expose the lead plates to the air will result in permanent damage to the battery. Maintain the electrolyte levels above the minimum fill lines on the battery and at or below the maximum line. A sealed VRLA (Valve Regulated Lead Acid) battery should be maintained with the same care as a conventional type battery with the exception of the addition of distilled water. Sealed VRLA batteries have a predetermined quantity of electrolyte added at the factory or in the field using the acid bottle specified for the battery. Once activated, the battery is permanently sealed and must never be opened.

Anyway ,as emphasizing at the beginning , a little bit of care and understanding of how your battery operates and is maintained will insure maximum service life.

Related Topics