Used Electric Car Batteries Can Now be Repurposed

MIT study shows new use for these batteries that are no longer sufficient for EVs.


(Courtesy MIT)

As electric cars grow in popularity, so do the amount of batteries that can no longer be used in vehicles due to their insufficient performance. A new study by the Massachusetts Institute of Technology (MIT) shows that these batteries can be repurposed as backup storage for solar operations.

While lithium electric batteries (EV) were designed to last 10 years, many degrade after only five according to McKinsey & Company. If these batteries can be reused or recycled (for their valuable metals), then they do not have to be disposed of.

The study, published in the journal Applied Energy shows that such a system could be profitable for both the electric car companies and the grid-scale solar operators. The researchers tested the idea on a hypothetical solar farm in California.

The researchers found that building the solar array with repurposed EV batteries that had declined to 80 percent of their original capacity, according to a MIT news release, could still run as back-up storage. And they would cost only 60 percent of the original cost of the batteries.

Testing this to scale is not that easy according to postdoc Ian Matthews who was one of a team of six researchers led by Tonio Buonassisi, head of the Photovoltaics Research Laboratory.

“There are many issues on a technical level,” Matthews said in the news release. “How do you screen batteries when you take them out of the car to make sure they’re good enough to reuse? How do you pack together batteries from different cars in a way that you know that they’ll work well together, and you won’t have one battery that’s much poorer than the others and will drag the performance of the system down?” 

He also said that there were multiple questions on the economic side: “Are we sure that there’s enough value left in these batteries to justify the cost of taking them from cars, collecting them, checking them over, and repackaging them into a new application?”

After using a model that showed battery degradation and could predict capacity loss in the EV batteries, the researchers concluded that it was both doable and economically feasible. In fact, the batteries could still be used when they reached 60 percent of their original capacity.

The researchers said that the amount of savings would vary depending on local regulatory and rates structures that they operate under.

Similar work is being done at the University of California. In January 2019, researchers devised a commercial-scale assembly of 15 Nissan Leaf batteries to store energy from a solar array according to T&D World.

This “second-life” system was developed by Professor Jae Wan Park and his graduate students at the UC Davis Green Technology Laboratory with a grant from the California Energy Commission. Finding a reuse for the EV batteries is very important due to the 2018 California 100 percent clean energy mandate.

Using less than optimal EV batteries for solar energy storage is a win/win strategy. This encourages the reuse of the growing amount of EV batteries as well as making solar energy more cost effective.

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