Rebuilt battery pack, red triangle

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by macman7500, Feb 24, 2026 at 5:23 PM.

  1. macman7500

    macman7500 New Member

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    I rebuilt the battery pack in a 2008 Prius and it's was fine for a week but later got the red triangle and #8 block has high voltage. Did I do something wrong when charging and discharging all the modules to refurbish them? I always dealt with low voltage modules but this is the first time it is too high. How can I prevent this error in the future?
     

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  2. JC91006

    JC91006 Senior Member

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    Is block 8 one that you replaced? There are probably multiple weak modules in the pack, so you might not have replaced them all. Also it's best to have the entire pack balanced afterwards, so all the voltages are the same/similar
     
  3. macman7500

    macman7500 New Member

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    I replaced around 10 modules and balanced all 28 of them. I had to do this job a few times because a few modules were leaking voltage on the bottom bolt so I put electrical tape
     
  4. JC91006

    JC91006 Senior Member

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    well the leaking voltage/fluid will be a major issue already. what is electrical tape suppose to do?

    This is a high voltage battery, and it requires quite a lot of skill to be able to successfully rebuild a bad battery. So be careful while doing what you're doing.
     
  5. macman7500

    macman7500 New Member

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  6. macman7500

    macman7500 New Member

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    Before I got a p0aa6 code and the car would not restart
     
  7. JC91006

    JC91006 Senior Member

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    The leak would definitely have caused the P0AA6. But what did you use electrical tape for?

    Remember the modules that you replaced, has to be replaced with KNOWN GOOD modules of similar capacity. Then after all that, you will need to balance them. Not sure your process to do all that, but it's not easy.
     
  8. Hayslayer

    Hayslayer Active Member

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    I've seen many modules that show voltage on the underside threaded insert that trigger the P0AA6. Sometimes these modules have been in excellent condition irt capacity and a person wants to save it. It can be reused merely by cleaning it very well, placing a layer or two of high quality electrical tape over the insert and then not installing that fastener screw when assembling. The tape insulates the insert from the case....thereby preventing the P0AA6 from triggering. Not high on my list of preferences, but it can work very well. I would consider it ok to do for a personal car, never for a customer.

    I've also seen batteries that have a layer of tape along the entire case, sandwiched between the case and module bottoms, with several fasteners missing. I would assume those modules are 'voltage leakers'.
     
  9. macman7500

    macman7500 New Member

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    This is exactly correct
     
  10. macman7500

    macman7500 New Member

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    I did balance them
     
  11. JC91006

    JC91006 Senior Member

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    I understand what you said you did, but since your battery failed, it was obviously not done right. It really is a very hard process to have a successful rebuild of a 2008, 18 year old battery. Swapping out 10 modules, leaves 18 modules behind that are 18 years old. And the 10 modules you used, all have to have similar capacities and are known GOOD. If if any of those 10 are bad, then you'll have even a bigger headache.
     
  12. JC91006

    JC91006 Senior Member

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    Well I don't consider using a band aid appropriate for a HV battery. You're just waiting for the next failure to come about.

    A better repair would be to spend $1000 on a used 2023 or new battery (off a rav4, sienna, whatever) and have all 28 modules the same age and capacity. That would be a long term reliable repair. Headache free for 10 years
     
  13. Hayslayer

    Hayslayer Active Member

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    I'm with you on that.
    Now, on the other hand, I understand not everyone is in the same financial situation. A single layer of Scotch 33 is rated for 600v. One or two (or even 5 or 10 underside fasteners spread out) being left out will have no significant impact on the integrity of the battery. The remaining fasteners are more than adequate for maintaining the pack inline.
    And guess what? From what I saw, the tape actually seals the bottom of the insert like a gasket, likely preventing any additional electrolyte seepage. Again, for personal use, if that's what the person wants, I'm ok with it. People have done far, far worse on HV battery rebuilds. Just look what people do when trying to work around a broken terminal stud on a module. Ever seen a busbar epoxied to a terminal stud?
     
  14. JC91006

    JC91006 Senior Member

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    The financial situation is definitely a game changer, have to use what you have in order to buy time. But most don't understand it costs way more long term to use a band aid than to do a proper repair. Imagine the costs of all the breakdowns and repeated repairs? Not to mention time wasted missing work or important events