Residual capacity estimation of stationary lithium-ion secondary battery based on its discharge voltage characteristics

The relationship between the residual capacity and the discharge voltage of a lithium-ion secondary battery having sufficient capacity to be used as a backup power supply in telecommunication applications is described. From results of high-temperature accelerated deterioration tests conducted on lithium-ion secondary cells, a drop in not only the capacity but also the discharge duration and the discharge voltage was observed, and a fixed relationship was found between the drop in discharge voltage and the residual capacity. This relationship was confirmed not only for single cells, but also for a multicell battery composed of 14 cells which was periodically discharged while being maintained at a floating charge. The possibility of estimating the residual capacity of lithium-ion secondary cells and batteries from a voltage measurement obtained in constant-current discharging was confirmed. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(3): 1–8, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20355