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did I toast the 12v battery?

Discussion in 'Gen 3 Prius Main Forum' started by trozei123, Sep 13, 2024 at 7:57 PM.

  1. trozei123

    trozei123 New Member

    Joined:
    Friday
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    Location:
    Olivehurst CA
    Vehicle:
    2010 Prius
    Model:
    Four
    My wife's 2010 Prius iv was completely dead this morning when she left for work. Lights were dim, dash would not light up at all. After several YouTube videos, I found that these signs point to the 12v battery being dead. I brought out a jump box to try and get the car to start, but had no luck.

    I removed the battery from the trunk area and brought it inside to put on my Viking automatic battery charger. I realized after about an hour on standard battery mode at 2 amps that I had screwed up. I had found out that these batteries are agm style. The charger showed that the battery had gone from a starting voltage of 9.8 up to 12.2. I took the battery out to the car to try it out. The car did turn on, but all the dash lights were lit up and the "ready" light didn't come on, nor did the engine start. I brought the battery back inside and set the charger to agm mode at 2 amps.

    I am worried that that original charge may have toasted the battery. It didn't feel warm when I discovered the mistake and took the charger off. Should I be worried about this and have to get a new battery? Or should it be ok to just try charging on agm mode at 2 amps for a few hours and see if that works?
     
  2. Brian1954

    Brian1954 Active Member

    Joined:
    Jan 31, 2021
    957
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    Location:
    South Central PA, USA
    Vehicle:
    2011 Prius
    Model:
    III
    You should be fine continuing the charge on the AGM setting. At a 2 amp charging current, you will need to charge the battery for about 12 hours or more for a full charge.

    How old is the 12v battery?
     
  3. AzusaPrius

    AzusaPrius Senior Member

    Joined:
    May 27, 2020
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    854
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    Location:
    California
    Vehicle:
    2010 Prius
    Model:
    IV
    Once you reconnect the 12v battery the car needs to reinitialize the ECU's by pushing the power button twice and waiting for the completion on the navigation screen.

    Then power off and start as normal.