Second Life Battery Pack as Stationary Energy Storage for Smart Grid

This paper presents the use of a second life battery pack in a smart grid-tied photovoltaic battery energy system. The system was developed for a single family household integrating a PV array, second life battery pack, grid back feeding, and plug-in hybrid electric vehicle charging station. The battery pack was assembled using retired vehicle traction batteries. The pack is configured with 9 cells in each parallel bank, 15 banks in series featuring 48V nominal and a 12kWh nominal capacity. Limited by the weakest bank in the pack, the second life battery pack has an accessible capacity of 10kWh, or 58% of its original condition. A battery management was developed to handle the bank-to-bank imbalance and ensure the safe operation of the battery pack. An energy management algorithm was established to optimize the energy harvest from PV while minimizing the grid dependence. An information network was constructed to acquire data from the battery, PV, major appliances, and major inverters using Zigbee and wireless qualified devices. The system presented here achieved utilization of used vehicle traction batteries for second round of application, optimization of solar energy harvest and supported electric vehicle charging.