Testing of Commercial Electric Vehicle Battery Modules for Circular Economy Applications 2017-01-1277

Increasingly international academic and industrial communities desire to better understand, implement and improve the sustainability of vehicles that contain embedded electrochemical energy storage. Underpinning a number of studies that evaluate different circular economy strategies for the electric vehicle (EV) battery system are implicit assumptions about the retained capacity or State-of-Health (SoH) of the battery. International standards and best-practice guides exist that address the performance evaluation of both EV and HEV battery systems. However, a common theme in performance testing is that the test duration can be excessive and last for a number of hours. The aim of this research is to assess whether energy capacity and internal resistance measurements of Li-ion based modules can be optimized, reducing the test duration to a value that may facilitate further End-of-Life (EoL) options. Experimental results for a Porsche Panamera Hybrid module and a Tesla Model S P85 module that highlight a reduction of the duration of a commercial battery module characterization test by circa 70%. This reduction is accompanied by levels of measurement accuracy for retained energy capacity in the order of 1% for module test temperatures equal to 25°C. Improvement of 85% is achieved for resistance testing while still retaining levels of measurement accuracy in the order of 2% for module temperatures equal to 25°C. Based on these experimental results, a quick characterization test sequence is proposed and within a robust system test framework would allow different organizations to prioritize the relative importance of test accuracy versus experimental test time when grading used Li-ion modules.