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12V battery when replacing HV battery pack?

Discussion in 'Gen 2 Prius Main Forum' started by PriusOwner428, Mar 26, 2022.

  1. PriusOwner428

    PriusOwner428 Junior Member

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    I've seen a lot of information on the replacement of the HV battery pack, but have not seen any mention of what to do about the 12V battery during the process. Does anyone know if the 12V battery needs to be disconnected or can it remain connected during the removal and installation of the HV battery pack? Would rather not disconnect it but, if it's dangerous to me or the electronics need to know. Thanks.
     
    #1 PriusOwner428, Mar 26, 2022
  2. bisco

    bisco cookie crumbler

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    almost every service proceedure in the service manul starts with, 'disconnect the 12v battery'.

    but is it absolutely necessary, or lawyer induced?

    seeing that the hybrid battery is not connected to the 12v until you power on, and the first thing you do when removing the hybrid battery is remove the orange safety service plug, it probably isn't necessary, but i do not speak from experience.
     
    #2 bisco, Mar 26, 2022
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  3. dolj

    dolj Senior Member

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    As you will at some point disconnect the battery ECU, it is probably prudent. Will it cause a problem if you don't, maybe not but why take a chance.
     
    #3 dolj, Mar 27, 2022
  4. Another

    Another Senior Member

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    The question that occurred to me is why not disconnect the 12v?
     
    #4 Another, Mar 27, 2022
  5. bisco

    bisco cookie crumbler

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    loss of a few memory functions, not a huge deal, but some like to avoid it if possible
     
    #5 bisco, Mar 27, 2022
  6. PriusOwner428

    PriusOwner428 Junior Member

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    It's mainly the lose of the few memory functions like the histories and radio stations. But the more I think about it the more I think it's not necessary. The orange plug actually would not have anything to do with it. It's there just to split the pack into two separate smaller packs so that if you do touch the wrong points it will just be unpleasant but not lethal. the only 12V inputs to the battery case would be the ECU power and the cooling fan power. Both of which are disconnected ahead of time. That's 2 or 3 plugs. When the car is powered off I don't think there's any critical monitoring of the battery pack by the car's systems.
     
    #6 PriusOwner428, Mar 27, 2022
  7. bisco

    bisco cookie crumbler

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    it is completely disconnected thru relays
     
    #7 bisco, Mar 27, 2022
  8. PriusCamper

    PriusCamper Senior Member

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    Regardless of disconnecting or not... First step is making sure you have a healthy 12v with no issues before you start working on hybrid battery. If you skip this check, you might be chasing down problems that don't exist anywhere but in the 12v.
     
    #8 PriusCamper, Mar 27, 2022
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