Second Life EV Batteries Quietly Back Up the Grid

Spent batteries from older electric vehicles are starting to pile up, but a handful of companies are repurposing them in a novel way: as energy storage for the grid.

These batteries are retired from EVs after their capacity falls 70 to 80 percent; that’s too low to satisfy drivers, but leaves enough juice for many stationary storage applications. With some clever engineering, hundreds of retired battery packs can be assembled into megawatt-scale energy storage systems.

June was a busy month for this nascent industry in the United States. On 4 June, Los Angeles-based B2U Storage Solutions announced it would repurpose used batteries from Waymo robotaxis for stationary grid storage. Two weeks later, Carson City, Nevada-based Redwood Materials unveiled a plan to combine about 100 used batteries from General Motors vehicles to provide 1.5 megawatts to one of the automaker’s plants in Michigan. And a week after that, Vancouver-based Moment Energy completed construction of what it says is the world’s largest EV battery repurposing facility.

The efforts address two significant needs in the energy industry: Grid operators need somewhere to store valuable excess energy from renewables, and the auto industry needs somewhere for old EV batteries to land. Second-life battery companies could satisfy both needs, if they can get the engineering worked out.

Second-Life EV Batteries Back Up the Grid

The first mass-market all-electric vehicles arrived in the early 2010s, and those batteries are starting to retire in increasingly large numbers. 130,000 EVs were sold globally in 2012, and that’s since skyrocketed to more than 20 million in 2025.

Sending spent batteries to landfills wastes valuable materials and years of remaining electrochemical life. Recycling—recovering metals such as lithium, nickel, cobalt, and copper to manufacture new batteries—is one option, but researchers have long argued that many batteries could provide additional value in less demanding applications, like second-life stationary storage, before being dismantled.

Stationary storage cycle more predictably and can tolerate slower charging and discharging rates, and a lot less current runs through them. Second-life uses include commercial backup power, microgrids, EV charging infrastructure, and, increasingly, grid-scale energy storage, such as storing excess renewable energy for later use and reducing demand during expensive peak hours.

Over the last decade, the second-life EV battery industry has been trying to move beyond small pilot projects and demonstrations into commercial deployment. But progress was slowed by a lack of retired batteries, labor-intensive testing and engineering, and uncertain economics that often made recycling or investing in new batteries more attractive.

In the last few years, diagnostic tools and testing procedures for evaluating battery health have improved, allowing companies to identify suitable batteries faster, more accurately, and at lower cost. On top…