A new lawsuit filed against Subaru and Toyota claims that the two automakers' jointly developed electric vehicles, the Solterra and bZ4X, suffers from an issue that causes the 12-volt battery used for accessories to repeatedly fail, with the plaintiff filing the suit claiming his vehicle has gone through multiple batteries in 5000 miles.

The class-action lawsuit, which was filed in the U.S. Eastern District Court of California, claims that Subaru and Toyota both knew about 12-volt battery problems before the the Bz4X or Solterra went on sale. Allegedly, these cars (from the 2023–2025 model years) drain and kill the 12-volt battery on a regular basis; despite that, the suit claims the two carmakers failed to warn customers or to fix the issues at hand.

The filing mainly focuses on this single owner's account. "The 12-volt battery equipped in Plaintiff Wade’s Class Vehicle has failed three times after only about 5000 miles of driving the vehicle. The 12-volt battery in Plaintiff Wade’s vehicle has been replaced twice since March 2023,"says the filing. The owner claims that the first failure happened within weeks of ownership; then the battery died again when it had around 2000 miles on it, and yet again around the 5000-mile mark.

Based on other accounts posted online, however, he's not alone when it comes to 12-volt battery issues. As one person with a 2024 example of the Solterra told the National Highway Transportation Safety Administration: "I have had the car since December of 2024, the car was a new lease. The battery has failed twice — once in January, and again last week. When I took it to the dealership, they said they replaced the battery, the new battery is now doing the same thing."

On Reddit, customers have been complaining about similar situations since early 2023. "At 6 months had the 12 volt battery replaced, now after 3 weeks getting low battery again," said one commenter. Another made a post in January alleging that since picking up the car in April of 2024, they've had a dead 12-volt battery three different times.

Interestingly, it doesn't appear as though the lawsuit in question defines what the central issue is between the 12-volt battery and the rest of the system. In other words, it doesn't define what the core defect, is aside from the 12-volt battery dying prematurely. Whether or not that factors into the suit's outcome is yet to be seen.

The electric Toyobaru siblings are hardly the only EVs to suffer from issues and allegations of problems with their 12-volt batteries in recent years. Back in 2021, Ford issued a service bulletin regarding a software problem that caused the Mustang Mach-E's 12-volt to drain while the car's propulsion battery was being charged, while earlier this year, an owner took to Reddit to claim that his 2021 Mach-E's 12-volt lost power and trapped his child in the vehicle. Meanwhile, back in 2023, Hyundai found owners of the Ioniq 5 complaining about unexpected 12-volt battery death, eventually pinning the problem down as one related to third-party applications pinging the car too frequently via Bluetooth.