State of health determination of sealed lead acid batteries under various operating conditions

In order to maximize the performance and life span of a battery, it is important to assess its state-of-charge and state-of-health. At elevated temperatures like those of desert climates in Arizona, states of extremely high or low state-of-charge can lead to irreversible damage in the battery. The focus of this research is to correlate the performance measurements typically collected to evaluate cycle life to state-of-charge and state-of-health values with high frequency impedance values, so that a more complete picture of a battery's overall status at a given time can be assessed. Batteries were subjected to temperature and charge/discharge rate variations and found that the state of health degradation was severe at high temperatures along with faster rate of charging compared to other evaluation conditions. Multiple linear regression analysis has also revealed that the degradation of the batteries is higher at elevated temperatures. Based on the experimental results on sealed lead acid cells, a portable tester using high frequency resistance values is also being developed for estimating the state-of-charge and state-of-health values for empowering the operators/technicians to more effectively manage the battery systems in the field.