An Approach to Recover Energy from Discarded Primary Batteries before being Disassembled

This study demonstrates the feasibility of recovering energy from discarded primary batteries (e.g., alkaline or zinc-carbon) that would be disposed of as normal household waste based on self-adaptive pulse discharge (SAPD) method. The SAPD approach is utilized to search the optimal pulse frequency and duty cycle for different types of used batteries with the maximum allowed discharge current. To assess the performance of the proposed approach, a prototype including improved passive cell balancing circuit, SAPD control circuit, and series-parallel switching circuit of supercapacitor banks was designed and implemented to drain a battery bank that consisted of at least 6 but at most 10 used cells of different brands in series. Discharging experiments showed that the energy recovery with six to ten used batteries ranged from 798 to 1455 joules, and the corresponding recovery efficiency was about 33.49~46.43%. Although outcomes are still far from being satisfactory in the efficiency with the proposed approach, the rate of energy recovery may depend on the remaining capacity of discarded batteries and so may be advantageous if the battery has a high remaining capacity. Therefore, authors conclude that there is possibly a direct link between the recovery efficiency and the remaining capacity of discarded batteries.