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Can I use the car itself to rebalance battery blocks?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by PLVNET, Feb 20, 2024.

  1. PLVNET

    PLVNET Junior Member

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    Hybrid Battery Woes and questions…

    A little over a year ago, I inherited my grandma’s ‘07 Prius w/ 90k miles on it. It had been sitting for awhile and (of course) the traction battery was toast. I paid to have a refurbished one put in. It came with a one year warranty and the car has been great, in fact, I kinda love this car.

    But, just like clockwork, 13.5 months later, I’m getting the red triangle of death again. Scanning with Dr. Prius gives me the P3000 code and it’s only showing one block that is the culprit. From what I’ve read, there’s still hope to get a grid charger and rebalance the blocks at this point. I went ahead and ordered a grid charger this morning, but I’m curious : in a case such as this, where it’s only one offending block out of 22 and the rest seem okay, has anyone ever attempted to rebalance the blocks with the car itself?

    The Hybrid battery doesn’t charge in neutral, but as the car runs in neutral, it’s draining the battery. Can I put it in neutral and just let it run until the other blocks get low enough to be more equal to the bad one and then pop it back in P and let the car recharge all of them?

    I ran a little experiment trying just such a thing earlier and it seems like the good blocks will discharge at a faster rate than the bad one. I actually watched the bars get closer together, but at 25% overall charge, the car starts screaming so, I was afraid to let it go much further and risk it not starting.

    Is there any precedent to this theory being plausible? How far can the traction battery drain before it’s a non-starter?
     
  2. bisco

    bisco cookie crumbler

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    I’m not sure even a grid charger will work after getting the triangle
     
  3. dolj

    dolj Senior Member

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    You mean one block out of 14 (or one module out of 28).
    Some have tried it and had mixed results. It doesn't really work the way you are describing it. Good blocks will never "catch up" to a bad module (within a block), you have a good chance of reversing the bad module. Once you have reversed the module it is unrepairable and at that point, you will be forced to open up the battery to replace the module with the reversed cell.
    That is not right. The good blocks will always discharge at a slower rate. It is the bad module (within a block) that will discharge at a faster rate than the others.
    See above.
    I don't know the answer for sure but as long as you do not turn the car off in this depleted state and allow the battery to recharge to above 40% SoC you should be able to restart the car on the next start. However, there are reasons why this is a bad idea, one of which is that the current at which the car will charge is too high when the SoC is below 40% and it may well cause irreparable damage to the battery.

    Just wait for your grid charger to arrive. You also need a method of being able to discharge the battery to various voltages as well.
     
  4. mr_guy_mann

    mr_guy_mann Senior Member

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    I have found that Dr Prius will not always pull codes from the HV battery ecu. P3000 is the Hybrid Control ecu saying "hey, the HV battery ecu has codes, go look there".

    You need a more capable scantool to see codes in all systems. Here's a thread that reviews several apps and devices.

    That said, I would expect the HVb ecu has a P0A80 (replace HV battery) or a P30xx (P3011 to P3024) - battery block "xx" (1 to 14) becomes weak.

    Your symptoms match that of a failed module (will be 1.0 to 1.5V lower than others when discharging - accelerating).

    A failed module is dead, I have never heard of any one "reviving" it.
    https://priuschat.com/index.php?posts/3290690

    Posted via the PriusChat mobile app.
     
    Brian1954 likes this.