ELECTRIC VEHICLES

Quantifying Second Life Battery Performance of Electric Vehicle (EV) for Stationary Energy Storage Applications

Batteries have been largely deployed in Electric Vehicle (EV) applications since the past decade. Based on the usage, the degradation occurred in the batteries are non-uniform in nature. State-of-Health (SoH) determines the deliverable capacity of the battery, when the SoH is less than 80% then such batteries can be considered as second life batteries. Post the end of first life, the remaining capacity of the battery can be extracted in low power applications by gauging the SoH. However, the longevity of the battery can be determined by Remaining Useful Life (RuL). Thus, SoH and RuL are the crucial terms to define in a second life battery during repurposing. Such mechanism are not clearly defined for quantifying second life battery performance. This project aims to estimate the SoH and RuL of second life batteries that are intended for stationary energy storage applications. Nissan Leaf and BMW batteries are considered in this research where the battery packs completed their first life in Electric Vehicle (EV) application. The scope of this work is to investigate the non-destructive test methodologies for SoH estimation through the electrical parameters such as Open Circuit Voltage (OCV), Internal Resistance (IR), Resistance Capacitance (RC) Models, and Impedance (Z) etc. The selection of electrical parameters that are to be monitored for SoH estimation holds the key from the repurposer point of view. The investigation method selected for SoH estimation mainly depends on the accuracy, effort required to compute the SoH and the time consumed. The outcome of this project would revolve around the investigation methods which determine the SoH and RuL from repurposer perspective. A set of protocols based on time and equipment will be developed at the repurposer’s facilities as SoH and RuL are the two key variables which determine the scope of the battery pack in second life.

Objectives:

• To investigate the SoH and RuL of second life battery pack
• To sort and grade the modules for based on SoH and RuL of second life battery pack
• To design second life battery pack for stationary energy storage application.
• To develop protocols to access SoH and RuL of the battery pack in second life.
• To deploy the second life battery for energy storage and analyze the data for improvement of the protocols.