Over Discharging Battery

Battery Application & Technology

In order to obtain maximum life from lead-acid batteries, they should be disconnected from the load once they have discharged their full capacity. The cutoff voltage of a lead-acid cell is usually around 1.75 V. However, the cutoff voltage is very sensitive to operating temperature and discharge rate. Like batteries discharged at a high rate will have a lower cutoff voltage than those discharged at a low rate. Greater capacities are obtained at higher temperatures and low discharge rates. The manufacturer should specify cutoff voltages for various operating temperatures and discharge rates.

Over discharge may cause difficulties in recharging the cell by increasing the battery's internal resistance. Also, over discharging may cause lead to be precipitated in the separator and cause a short in the cell or between cells.