System Is Currently Undergoing Testing Ahead of Full Deployment
The lifecycles of battery packs and the electric cars or hybrids they're installed in don't necessarily match. A pack can degrade too much for continued use powering a car, or conversely the car could reach the end of its usable life or be damaged in a crash. Either way, it leaves batteries that might still have some useful life left—and the question of what to do with them.
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Toyota wants to use them as a supplementary power source for factories. The automaker has been developing its Sweep Energy Storage System, based on arrays of used EV or hybrid batteries, for several years and has now started field tests at Mazda's main factory in Hiroshima, Japan.
Helping Boost Renewable Energy Use
For now, Toyota is monitoring the stability of charging and discharging cycles to see if the battery-based energy storage system will be up to the task of powering the Mazda factory (or at least helping to do so). According to a Toyota press release, the goal is to use this energy storage system as a buffer for the factory's solar array, providing consistent power at all times by absorbing excess energy and discharging it when needed.
Using batteries for this purpose is nothing new, but what's interesting about Toyota's approach is that it maintains the energy management systems from the donor vehicles. That eliminates the need for a separate, new system, and theoretically allows for battery packs with different cell types, chemistries, and different states of health to be used together. That's important, given that Toyota won't able to control which batteries end up in the discard pile.
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Why is Toyota testing this hardware at a Mazda factory? The release didn't explicitly say, but it's worth noting that the two automakers have corporate ties. Toyota owns a small stake in Mazda, and they've previously collaborated on projects like a joint Alabama factory and the powertrain for the Mazda CX-50 Hybrid, which uses Toyota components.
Reuse Vs. Recycling
So-called "second life" uses of battery packs for energy storage and supplementary power have been a regular presence in automaker public relations copy since the dawn of the modern EV age. However, in most cases they've been small-scale, one-off efforts, like Toyota's repurposing of old hybrid battery packs to power a cluster of buildings at Yellowstone National Park, or Porsche's more recent use of batteries from pre-production Taycan EVs to help power one of its German factories.
This long list of proof-of-concept cases hasn't stopped a debate about whether reuse or recycling is the better option for used EV batteries. Companies like Redwood Materials—which was founded by former Tesla executive JB Straubel and has contracts with Toyota and a handful of other automakers—aim to strip raw materials out of used batteries as a more environmentally friendly alternative to mining and processing new materials for continued battery production.
However, the biggest hurdle for both approaches might be an insufficient supply of used batteries. EVs and hybrids still represent a minority share of new-car sales, leaving a relatively small supply of batteries in circulation. That's why, in a 2021 report, research firm Wood Mackenzie predicted that battery recycling wouldn't become a major business until 2030. And that was before anti-EV, anti-trade policies put in place by the Trump Administration that could curtail EV sales.
This story was originally reported by Autoblog on Aug 24, 2025, where it first appeared in the News section. Add Autoblog as a Preferred Source by clicking here.
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