4. Overdischarging Lithium-Ion Batteries

A main objective of the project LithoRec II is to study the overdischarge of Li-Ion batteries for the purpose of recycling. For safety and functional reasons, the batteries need to be overdischarged before undergoing the process steps of disassembly and crushing. In this study, various devices for overdischarging are set up and investigated together with corresponding battery behavior. Device properties such as cost, safety, discharge time and discharge flexibility are assessed. Furthermore, the study focused on parameters like battery heating during discharge and pole reversal, relaxation amounts and heights as well as short circuit currents. The investigations show, that it is most advisable to discharge whole battery systems by energy recuperation into grid with electronic adjustable loads, because of efficiency and safety reasons. Overdischarging is not problematic if crucial battery parameters are observed. It is recommended that overdischarging of automotive traction batteries should only be done by high-voltage specialists.