Cost-Effective Integration of Second-life EV Batteries with Solar PV Systems for Commercial Buildings

Developing battery management system technologies, algorithms, and operation strategies to extend the second-life of EV batteries.

sdsu cec project

Tech Partner

San Diego State University Research Foundation


San Diego, CA

Recipient Location


Senate District


Assembly District



Amount Spent



Project Status

Project Update

SDSU have completed about 5430 aging cycles after 17 months of aging tests of the second-life batteries, which is equivalent to 17.8 years of real operation. SDSU is in the process of validating the second-life EV batteries for PV storage applications.

The Issue

California has the goal of 5 million zero-emission vehicles on the road by 2030, meaning that over the next few decades, a large number of used electric vehicle (EV) batteries will need to be recycled. EV batteries are typically retired from their first life when the battery performance decreases to 70-80 percent of its initial capacity. Research has indicated that second-life batteries paired with solar photovoltaics (PV) and demand response could be economical. Moreover, lower-cost second-life EV batteries may enable small businesses with buildings under 30,000 square feet to install PV-battery systems and may lower energy costs for California ratepayers.

Project Innovation

This project pairs second-life EV batteries with a solar PV system and develops key technologies to quickly identify battery health and optimize usage. These key technologies include developing control and operation algorithms to enable 1) proactive maintenance, 2) predictive thermal management, 3) active cell balancing, and 4) dynamic demand response management. Together, these technological advancements extend the life of the repurposed EV batteries and lower the cost to California ratepayers. The goal is to ensure that second-life EV batteries will last for a minimum of 10 years as part of a grid storage application with a degradation rate of 3% or less annually.

Project Goals

Characterize the Degradation Rate of Second-life EV Battery Cells.
Validate the Second-life EV Battery Paired with Behind-the-Meter Solar PV.
Develop and Demonstrate Technologies, Algorithms, and Operation Strategies.

Project Benefits

The project is developing battery management system technologies, algorithms, and operation strategies that enable second life EV batteries to last for a minimum of 10 years with a degradation rate of 3% or less annually. The battery management systems and second life batteries will be tested at two pilot test facilities where the battery management algorithms and hardware will be deployed. The technological developments from this project will increase the versatility, lifetime/durability, and efficiency of second life EV batteries while also lowering the total cost of these systems.

Lower Costs


This project will help commercial customers significantly reduce their electricity bills through novel battery energy storage system operating and sizing algorithms, thus promoting the deployment of lower-cost energy storage syst

Greater Reliability


This project is demonstrating and validating that the second life EV battery integrated with solar PV can operate reliably, support grid needs, and provide energy resilience to commercial buildings to serve their critical energy

Key Project Members

Chris Mi

Chris Mi

Professor and Chair
San Diego State University



The Regents of the University of California, San Diego

Contact the Team