Deterioration measuring method of VRLA battery used in UPS systems

Valve-regulated lead-acid (VRLA) batteries are used in telecommunications networks for standby power systems. An advantage of VRLA batteries is that they are maintenance-free. On the other hand, these batteries are completely sealed, which makes it extremely difficult to determine deterioration levels. 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, and it is accurate to within 10%, and is compact, light, and easy to handle. However, as this method measures minute levels of resistance, precise measurements are difficult under high noise environment such as UPS systems. This paper describes the types of noises applied to VRLA batteries in telecommunications power supply systems. It also introduces a method whereby measurements are conducted while high noise exists.