Looking for others with 12V battery problems for class action lawsuit

Discussion in 'Gen 5 Prius Main Forum' started by Rick B., Jun 4, 2026 at 7:09 PM.

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  1. Rick B.

    Rick B. New Member

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    I owned a Prius from 2015 to 2025, then purchased the new 2025 Prius in May 2025 and originally loved it. But in Feb 2026, I went on a 2-week vacation and returned home to a dead car, due to 12V battery with no juice. I had it jumped and didn't think there was a problem. But in April, I was on another 2 weeek trip, and returned home to same problem -- car was dead. Took it to Toyota dealer who replaced the 12V battery under warranty. But they insisted I had to get someone to start the car at least every 2 weeks. No one told me this. The sales person who sold me the car never said this. As a prior Prius owner, I never had to do this. I travel a lot and do not have easy access to people who can come start my car and spend 30 minutes with it while I am gone. There is an entry in the manual on page 420, but if this is a true warning, it needs to be on page 1. This is not the car I thought I was purchasing. Anyone else have this problem? I am thinking of a class action lawsuit against Toyota, as this is a radical departure from past Prius models that was not revealed when purchasing the car.
     
    #1 Rick B., Jun 4, 2026 at 7:09 PM
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  2. Gokhan

    Gokhan Senior Member

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    This has been posted here many times.

    The problem occurs when the car sits at the dealer lot for too long before it is sold, or when it is not driven frequently. Once the 12-V battery SOC drops too low, the 12-V BMS will no longer fully charge the battery.

    The solution is simple. Get a Noco Genius battery maintainer and hook it up when you first buy the car, then again every few months. This will ensure the battery stays fully charged.
     
    #2 Gokhan, Jun 5, 2026 at 3:19 AM
  3. VelvetFoot

    VelvetFoot Senior Member

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    I was fooling around with the car yesterday. Removing the negative lead off the battery only causes loss of tank mpg, far as I can tell, on my LE. No big deal to open the rear door with the interior handle, fold down seat and reach in and put lead back on. I guess you could do this on a locked car, opening the door with the mechanical key.
     
    #3 VelvetFoot, Jun 5, 2026 at 7:02 AM
  4. TinyTim

    TinyTim Active Member

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    I am curious to how well a Gen 5 Prius would do with an AGM battery vs. the stock flooded 12v battery. Maybe it solves the problem? Otherwise it could be a Toyota software problem in the car. They can fix how the car interacts with the 12v battery while not being driven regularly.
     
    #4 TinyTim, Jun 5, 2026 at 7:58 AM
  5. BiomedO1

    BiomedO1 Senior Member

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    I believe that the 12V battery is classified as a wear-out item; like the tires and brakes - but I wish you Luck in this endeavor..........

    The easiest way to manage this issue is to connect the car to a RV battery tender, whenever your gone for more than a week. That should resolve your issue. There's also a TSB for the PHEV version that places their systems in "sleep mode" faster to prevent 12V battery discharge.

    Hope this helps.....
     
    #5 BiomedO1, Jun 5, 2026 at 10:50 AM
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