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Interesting quirk with battery replacement

Discussion in 'Gen 3 Prius Technical Discussion' started by defrankond, Sep 1, 2016.

  1. defrankond

    defrankond Member

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    2010 Prius
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    IV
    today I replaced the stock OEM 12v battery in my Prius since it was producing hydrogen sulfide and getting weak. I replaced it with a yellow top optima like with all my pri. But this is the first time I experienced this particular issue and maybe someone can shed some insight on it.

    Battery was put in and everything went well, got in to start the car but instead of going into ready it went to accessory mode showing 6 bars on the hv battery gauge. I shut the car off and started it again and at this point it went into ready and all systems normal, but the odd part is the HV battery went down to two bars, the engine kicked on and charged it up to 4 then kicked off. Sat there for 15 min with it on and it didn't loose any bars so I'm assuming it did a recondition cycle?

    Another interesting thing is my fuel counter went from 416 miles till empty to 613.
     

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    #1 defrankond, Sep 1, 2016
  2. Mendel Leisk

    Mendel Leisk EGR Fanatic

    Joined:
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    Vehicle:
    2010 Prius
    Model:
    Touring
    Did you use some sort of "memory saver" when disconnecting the old battery, ie: connected some auxiliary 12 volt source during the swap, to maintain settings/memories? If not: for sure you last sentence would be due to the disconnect. And perhaps more?

    If you've got a jump pack with cigarette type outlet, one of these OBD connector cables is the rolls Royce way to go. They typically have indicator light(s) to confirm good connection.

    image.jpeg
     
    #2 Mendel Leisk, Sep 1, 2016
    Last edited: Sep 1, 2016
  3. defrankond

    defrankond Member

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    No I just disconnected and replaced. I know it doesn't hurt anything and probably will give the system a nice fresh start. I'm just gonna have to deal with it relearning everything now which isn't a issue. The system is functioning wonderfully though. My Mpg's have gone back up, engine cycles like it should and it seems to be quite happy with its new battery.
     
    #3 defrankond, Sep 1, 2016
    Mendel Leisk likes this.
  4. JC91006

    JC91006 Senior Member

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    Whenever you disconnect the 12v, it resets itself. On the battery SOC, it would assume the charge is in the middle somewhere......then after it detects the actual reading, it'll adjust itself.

    Same thing with the fuel gauge DTE, it's self adjusting after it redetects after a reset. There's probably a memory of how you drive and then it determines the DTE. Once it's reset, it loses your driving habits and pattern. But the DTE is never accurate so why bother
     
    #4 JC91006, Sep 1, 2016
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