Online SOC Estimation of Battery for Wireless Tramcar

SUMMARY Wireless tramcars (battery-driven tramcars) are developing to the actual application stage. The most important information to be considered while operating a wireless tramcar is the state of charge (SOC) of the battery. The purpose of this study is to develop an online method for SOC estimation. This method employs a new equivalent circuit of a lithium-ion battery. SOC estimation using a conventional equivalent circuit results in a large error during fast current transients. In order to improve the accuracy of the estimation, we propose a new equivalent circuit of a lithium-ion battery. Because the parameters of the proposed equivalent circuit depend on temperature, we propose a new method for SOC estimation in which the temperature estimation is taken into account. This method requires only instantaneous values of the voltage and current, and therefore no temperature measurement is required. Experimental results show that the accuracy of the proposed method is significantly improved when the temperature is taken into account. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(2): 83–89, 2014; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21174