Residual energy extraction from near end-of-life lithium-ion batteries using a self-adaptive pulse discharge method

A modified self-adaptive pulse discharge (SAPD) method is adopted by this study to examine the feasibility of extracting residual energy from near end-of-life non-reusable lithium-ion batteries before disassembled. The SAPD model is used to determine the optimal frequency and duty cycle in the process of energy recovery, so the highest pulse discharge current can be obtained. A prototype including an improved active cell-balancing circuit, a modified SAPD control circuit, and a supercapacitor module switching circuit is developed to extract a battery bank that consists of at least one and at most 12 cells in parallel to reduce the discharge current as well as prevent damaged circuit components. The results of testing Sanyo UR14500P batteries show that the energy recovered from six to 12 cells ranges from 2630 to 2955 joules, and the corresponding recovery efficiency is from 64.97 to 66.19 %. Besides, with a randomly selected eight-cell pack, the SAPD method yields higher recovery efficiency than the short circuit discharge and pulse discharge methods, and the recovery efficiency increases by 11.74 % and 9.39 %, respectively. Although the results presented are far from being satisfactory from the perspective of efficiency, this study serves as a starting point for reusing and recycling resources.