Electrical Engineering ⇒ Topic : Charging rate.

Charging rate. What should be the value of charging current? The answer is that it may be as high as the battery can take without excessive 'gassing' or heat. Too great a charging current may produce excessive heat. This will cause plates to buckle and short circuit may occur. Also the water of electrolyte will be lost due to electrolysis and evaporation, raising the concentration of sulphuric acid left behind. The strong acid then may char the separators, causing permanent damage to the battery. The temperature of the electrolyte should not be permitted to rise above 40°C. Efforts should be made to use the charging current value recommended by the manufacturer. In case it is not available, one of the following thumb rules may be applied :

• The charging current should be 1 A for every positive plate of a single cell. Thus, if the cell contains 13 plates, six of them will be positive. The charging current for the battery should, therefore, be 6A.
• The charging rate should be such that full charge can be obtained in 8 hours. Thus 100 Ah battery should be charged at the rate of 100/8 = 12.5 A. This will ensure the maximum life of the battery.