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2008 Prius Bad Hyrid battery after water issue

Discussion in 'Gen 2 Prius Main Forum' started by jfs2010, Apr 24, 2024.

  1. jfs2010

    jfs2010 Junior Member

    Joined:
    May 29, 2010
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    Location:
    Westchester, NY
    Vehicle:
    2008 Prius
    Model:
    N/A
    Yesterday, I posted about trading in my 2008 prius with116K miles and a bad hybrid battery with dashboard lights displayed, but want to follow up with what led up to the issue as I'm perplexed that the hybrid battery went bad a month after the first issue began.

    Two month ago, the car was driving great, brought it in for the annual inspection and it passed with flying colors. So all was good.

    A week after the inspection, we had a terrible rain storm and the next day the red triangle of death showed up along with vsc and other warning lights. The car is not garaged. After searching youtube, I discovered that the 12v battery well may be filled with water so I checked and sure enough it was. I drained it, dried it out, sealed up all the areas that could be leaking water, and all the dashboard lights disappeared about an hour later.

    The car ran great for about a month, until the dashboard lights reappeared last week.

    I checked the 12v battery, and the voltage was low, noticed the car clock was off by several hours, so I brought it in to the mechanic to get it replaced. Unfortunately, the new 12v battery did not turn off the dashboard lights, so the mechanic ran tests and told me cell #2 and 3 of the hybrid battery were no good. I also did a test on Dr. Prius and it gave me battery code P3000, no engine codes and I can see the same issue with cell 2 and 3 which at times displayed a -14.4 voltage during the test to a +14.9 voltage.

    I road tested the car on the highway yesterday, and the acceleration was hesitant, jerky, almost felt like a transmission problem I had in my old ford, but once accelerated it ran nice, recharged the hybrid battery fully per the dashboard, and I got up to 41 mph. Just took a local drive around my neighorhood and it ran great. Wasn't accelerating so I didn't feel that issue.

    I'm perplexed about the hybrid battery issue as the car issues all seemed to have started when the 12v battery well filled up with water. Could the water have affected one of the hybrid battery connectors so that the car is not able to read cells 2 & 3? I saw some youtube videos that there is a metal box at the end of the hybrid battery that could possible have a short, and also another connector to the hybrid battery fan (above the 12v battery area) that shorts due to water leaking on it. I don't believe my mechanic looked at any connectors to see if an issue is there. Thanks again for any advice.
     
    #1 jfs2010, Apr 24, 2024
  2. TMR-JWAP

    TMR-JWAP Senior Member

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    Vehicle:
    2007 Prius
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    Touring
    This is an easy one. A module in your HV battery cannot have a "true" negative voltage. This only happens when there is a failure in the voltage sensor harness or there is corrosion on the pins in the ecu socket where that harness plugs into. that ecu is inside the HV battery case.
     
    #2 TMR-JWAP, Apr 24, 2024
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  3. Tombukt2

    Tombukt2 Senior Member

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    2009 Prius
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    Base
    The water you're getting in your battery well is because you need to feel around and the battery well and you'll see some rubber plugs You just need to push them out they'll fall into a well Don't worry about it You have no water passing through you have water coming in and standing standing is bad passing through is good over on the other side where the little tool compartment is there's some rubber plugs over there You should push them through. Remove the spare tire and right under where the hybrid battery goes but in the spare tire well there is a rubber plug You should push it through reach under the car grab it and throw it somewhere in the car maybe in that little tool compartment opposite where the battery is on the other side. You want water when it gets in the car to go through the car like the car's not there That's what these drain holes and whatnot are for If they're all plugged up then you get what standing water that's like what mosquitoes and bugs grow in probably don't want that in your car and the battery well for the 12 volt I even drill a couple little extra I don't know 5:30 second to quarter inch holes where if I pour water from a pitcher into that well where the water runs to and wants to stay I put a hole now water can't stand at that battery it'll freeze in the winter and ruin the 12 volt happens to Prius is on this list all the time every winter. So create the natural pass through for the water and the be no problems there's always going to be some moisture getting in some kind of way You can seal you and seal you and seal. But people still get water coming in so just make it pass through and you'll be okay so more than likely you've had the terrarium effect going on up in Westchester inside of your car and when you pull your battery and take the top cover off you're going to probably see some frosted nuts and corroded bus bars and things like that That's not conducive to good electricity flow and things like that and then of course you'll check your HVECU open it up look for the nastiness on the bus bars and the pins inside the ECU case clean that mess up It's probably fine. We've had to do this on almost every generation to we have purchased we have four.
     
    #3 Tombukt2, Apr 24, 2024
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  4. jfs2010

    jfs2010 Junior Member

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    Vehicle:
    2008 Prius
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    Fanscinating!! I will definitely look into this more and bring the issue back to my mechanic. Would this also affect the acceleration? It was a bit sluggish getting on the highway. Never had that happen before. Thanks.
     
    #4 jfs2010, Apr 24, 2024
  5. jfs2010

    jfs2010 Junior Member

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    N/A
    Yes, I was able to clean up and remove the plug and water from the wheel well, but couldn't reach the plug in the battery well. I used a turkey baster to remove the water there! LOL!! We've had a few more storms since and the battery well has stayed very dry but I will keep an eye on that as well.
     
    #5 jfs2010, Apr 24, 2024
  6. Brian1954

    Brian1954 Active Member

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    Model:
    III
    You have the same problem as the person from the UK in this thread: https://priuschat.com/index.php?posts/3437054
    There is a nice video in the thread showing the Dr Prius app with negative voltages on block #2 & 3. To fix your problem the voltage sensing wire harness and the battery ECU should be replaced.
     
    #6 Brian1954, Apr 24, 2024
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  7. bisco

    bisco cookie crumbler

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    yes, corrosion can affect performance
     
    #7 bisco, Apr 24, 2024
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  8. jfs2010

    jfs2010 Junior Member

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    Thank you so much!! I will look into this.
     
    #8 jfs2010, Apr 24, 2024
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