Battery Management for the Electric Hydraulic Pump System of a Lifting Trolley

This study proposed a battery management approach for the electric hydraulic pump system of a lifting trolley. The pump system was powered by two 12-V lead-acid batteries in series. Because direct measurement of the actual battery state of charge is unlikely, it has mostly been determined through estimation based on the measured open-circuit voltage. A discharge current will result in a voltage drop and hence a lower voltage during discharge; however, the battery voltage will return to the original open-circuit voltage once the discharge stops. The operating current of the electric hydraulic pump system employed in this study was associated with three factors: the lifting height, lifting load, and battery state of charge. The operating current remained constant during the first half of the lifting phase and increased gradually with the lifting height in the second half. The operating current peaked when the lifting height reached the maximum. The power management approach for the electric hydraulic pump system featured the following basic functions: overcharge protection, overdischarge protection, short-circuit protection, overload protection, and an operating timer established in accordance with the system’s operating current variation. According to the manufacturer-defined maximum lifting load and lifting height of the lifting trolley, this study conducted experiments to obtain the maximum required operating time. An operating time greater than the maximum required operating time indicates the occurrence of an unexpected event, discharge should be stopped until the fault is resolved.