A deterioration estimating system for 200-Ah sealed lead-acid batteries

The introduction of sealed lead-acid batteries, which do not need refills of water, greatly reduces the amount of maintenance required. However, it is difficult to estimate the battery´s deterioration because they are sealed. A useful battery test system for estimating the battery deterioration was developed in NTT and NTT Power and Building Facilities Inc. It can measure the battery´s capacity in less than 1 ms without affecting telecommunications equipment or power equipment, is accurate to within 10%, and is compact, light, and easy to handle. In this system, the battery´s internal resistance which is calculated from the transient voltage change at the battery´s terminal, and current which flows through the circuit, is used to determine the extent of deterioration in the battery. The pulse width of the transient voltage was set to some hundreds microseconds from the mutual relationship between the voltage drop and the battery´s capacity. A regression expression was developed using batteries with artificially accelerated deterioration, and a total of 250 sets of 200-Ah sealed lead acid batteries now in use were applied for field experiments. Errors of less than 10% were achieved for every brand of battery. We also verified that neither telecommunications equipment nor power equipment was affected by this measurement