This thesis studies the operating characteristics of lead acid batteries with the intermittent discharging current. Rest time is added periodically on purpose during the battery discharging to observe its impact on the releasable capacity. From the experimental results that take the frequency and the duty-ratio as two variables, batteries with the intermittent discharging at high frequencies or low duty ratios can release more capacity. The results also indicate that the depth of discharge (DOD) affects the intermittent discharging. More capacity is released while approaching the end of the discharging, whereas no clear difference is found in the beginning. Last but not least, the average current is proved experimentally to play a significant role in current discharging. With the same average current, the maximum capacity obtained from the intermittent current discharging is close to that from the constant current discharging.

This thesis proposes an enhanced ampere-hour counting method based on the depth-of-discharge (DOD) to estimate the state-of-charge (SOC) and state-of-health (SOH) for lead-acid batteries. Not only the losses at different discharging currents, but also the releasable capacity at the exhausted state caused by the larger discharging current are considered and compensated. Furthermore, the SOH is revaluated at the exhausted state by the maximum releasable capacity, consequently leading to more accurate SOC estimation. Through the experiments that emulate practical operations, the experimental results reveal that the maximum error is less than 6 %.