Nissan has a plan for used Leaf batteries: powering buildings

• Many wonder what will happen when an electric car battery is no longer useful for the vehicle.

• Of course, EV batteries can be recycled — but they can also be repurposed for energy storage.

• Nissan is partnering with startup Relyion Energy to ensure its used Leaf batteries are put to good use.

One of the biggest challenges to the auto industry's multi-billion-dollar push to electrify lies in the batteries. What happens when millions of used electric car batteries aren't useful in a vehicle anymore?

Nissan's latest move with a budding startup in the battery-repurposing space could be a solution to that looming problem. It might also answer concerns people have about the impact of EVs on the grid.

Nissan will work with Bay Area-based startup Relyion Energy to retire batteries from its well-known Leaf EV, Relyion announced Monday.

After all, used batteries are chock-full of valuable materials like lithium, nickel, and cobalt. And one estimate suggests that used batteries still have about 80% of their life left even after juicing an EV for several years.

But a lot of expense and resources were used to make functioning EV batteries. If it doesn't make sense to tear a battery apart in order to recycle its materials once it can't power an EV anymore, it could still be used in other ways.

Through Nissan's 4R business (a division established in the early days of the Leaf that includes recycling, reuse, reselling, and refabricating), Relyion will be charged with taking spent battery packs recovered from Leafs, testing their level of health and state of charge, and putting them in second-life energy storage.