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California is testing reuse systems to head off anticipated flood of retired electric car batteries

Chis Mi.jpg
Thomas Fudge
Engineering professor Chris Mi kneels next to a used electric vehicle battery in his lab at San Diego State.

A lab at San Diego State University is filled with bundles of wires, some of them attached to battery cells being tested.

Near the center of the room is a black, steel case containing about 300 of those cells and weighing more than a thousand pounds.

It’s a car battery that once inhabited a Nissan Leaf.


Now imagine a million battery cases like that being dumped into California’s waste and recycling stream every year, as electric vehicles and their batteries reach the end of their lives.

Something like that will start happening after 2035, when Governor Gavin Newsom’s executive order takes effect. The measure requires all new passenger vehicles to emit zero carbon emissions and be powered, most likely, by car batteries.

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The need to reuse and eventually recycle all those batteries has forced researchers to try to answer the question of what can be done with the old batteries.

It means the state needs to find a way to extend the life of those battery packs by finding another use for them.


“Some of them may have enough power and energy capacity to use for an energy storage project,” said San Diego State Electrical Engineering Professor Chris Mi. “If you extend their life for another ten years, you can delay the whole life cycle of the battery.”

When Mi speaks about using the batteries for energy storage, he’s talking about storing solar energy. The California Energy Commission (CEC) is sponsoring four demonstration projects for repurposing electric car batteries. Two of them are in San Diego county.

And storage of solar energy, to use when the sun doesn’t shine, is the research focus of San Diego State University scientists, and also those at Smartville, Inc. in Carlsbad, home to the other local CEC demonstration project.

Car batteries are well suited for energy storage, even after 10 years of use in a vehicle, according to Mi.

Reuse turns them into a solar-energy bank for businesses and agencies that can make withdrawals whenever it makes practical sense.

Solar energy stored on site also replaces the problematic system we currently have for dealing with excess solar energy.

“Now we have to send it back to the grid. And they may not like it because it creates instability for the grid, and nobody uses it,” Mi said.

Lithium-ion car batteries are typically retired when an electric car loses that crucial mileage range that drivers depend on, according to Kevin Wood, a professor of mechanical engineering at SDSU. But the batteries still have 60% to 80% of their energy life left.

Wood offers a scenario where a car battery may require 100 units of energy to be created, through mining, manufacturing and transport.

“If we can take it out of an electric vehicle, we can use it for another 500 units of energy in a grid-scale storage application. Now when we say it cost us 100 units of energy to make, we’re able to get 700 units of energy out of the life of this battery. That’s a lot more sustainable future.”

California officials seek a statewide solution

California is leading the way in the use of electric vehicles. The governor's office reports California has 10% of the nation’s cars but 40% of all zero emission cars

Caroline Godkin is Deputy secretary for environmental policy at CalEPA and, for two years, she has led the Lithium-Ion Car Battery Recycling Advisory group.

Used up EV car batteries are hazardous waste, according to Godkin. As such, the battery's elements ultimately need to be recycled to have a second life as an energy storage vessel.

“As you think about our circular economy, and the critical materials that are in these batteries, they are also a source of these critical materials to be put back into the manufacturing process. We have this great opportunity right now, when we think about these products, to keep them out of landfills… to keep them back in the value train,” Godkin said.

Those valuable materials include lithium, cobalt, nickel and manganese, all of which must initially be mined.

Even in California, electric vehicles make up a small proportion of all cars and trucks. Godkin said that’s why we have yet to see a mass retirement of EV batteries, which she said will start coming in 5 to 10 years.

“What we have — the opportunity to do right now — is to put in place the policies working with industry partners and our other partners to get it right,” Godkin said.

Scientists Chris Mi and Kevin Wood say one key issue to address is finding a way to make car battery reuse economically feasible.

China exports newly mined lithium iron phosphate batteries which are not ideal for car batteries, but they're quite inexpensive and good enough to use for solar energy storage.

“We have to figure out how to minimize cost,” Wood said. “Sustainability and cost are two really, really important things, and they’re not always correlated, right? Sustainability sometimes costs more money. So there is going to be tension between these two, and there are challenging debates we are going to have to have. And the reality of the situation is that cost, a lot of times, wins.”

And those challenging debates are about to take place in Sacramento.

CalEPA’s Lithium-ion Car Battery Advisory Group expects to finalize its report on reuse and recycling of batteries this month. Then the findings will be passed to the California Legislature, with the expectation that policy will follow.

Among the big questions: Who will be responsible for dealing with the battery’s reuse or recycling? The car manufacturer or the company that removes it from the car?

Wood says that is one of several challenging debates people will have to have before 2035, when all new cars in California will have to be zero carbon emission.

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Updated: March 28, 2022 at 3:15 PM PDT
Editor's note: A previous version of this story said "China exports newly mined lithium ion phosphate batteries... " It should have said China exports ``lithium iron phosphate batteries." KPBS has corrected the story and we regret the mistake.