Viability of “second-life” use of electric and hybridelectric vehicle battery packs

In order for successful second-life implementation of Electric Vehicle (EV) battery packs, the viability of the intended second-life use must be ascertained based on a cost-benefit analysis and technical appraisal of the estimated condition of the available battery packs. This paper discusses the issues in measuring State-of-Health (SoH) and other battery condition metrics of a battery pack. Measurements on real-life battery packs sent for recycling are taken that demonstrate a typical 85% SoH; slightly higher than predicted by Original Equipment Manufacturers (OEM). A model is introduced that can simulate the energy demand in a home/dwelling being met by a number of sources including mains (utility) power, photovoltaic generation (PV), and second-life battery storage. The model is applied to three scenarios using second-life battery storage, to create energy costs savings through time-shifting of energy using on-peak/off-peak electricity tariffs. For each scenario a cost-benefit analysis is produced, indicating that whilst energy costs savings can be achieved, excessive usage of the battery pack can cause the payback period of the capital investment to be longer than the predicted second-lifetime of the battery pack. However, the final scenario demonstrates that combining the battery pack with local generation, such as PV, yields cost savings that are significant at 75%, and the payback period is within the estimated lifetime of the battery pack.