Effects of Standtime on the Available Capacity of Lead-Acid and Nickel/Iron Electric Vehicle Batteries

摘要

In electric vehicle (EV) applications, the battery load typically contains interruptions of various time durations. These standtimes affect the battery's available capacity and must be understood in order to predict and optimize vehicle operation. Laboratory tests were conducted to measure the impact of various standtimes (0-4 h) at different depth-of-discharge (DOD) and state-of-charge (SOC) levels on the capacity retention of both improved lead-acid and nickel/iron (Ni/Fe) EV batteries. The results showed that the Ni/Fe system exhibits a self-discharge capacity loss immediately after charging that increases with both standtime and SOC. Fortunately, the self-discharge rate decreases rapidly with standtime and discharging. Standtimes after charging also decrease the available capacity of the lead-acid system due to reduced battery temperatures. However, standtimes at DOD levels > 50% provide an increase in battery capacity by allowing for the relaxation of electrolyte concentration gradients. This paper describes the test procedures used, presents the test data, and discusses the results. (ERA citation 09:033374)