Is there a proper sequence to recharge individual hybrid-modules?

Discussion in 'Gen 2 Prius Main Forum' started by priuslyfe, Apr 22, 2026 at 8:58 PM.

  1. priuslyfe

    priuslyfe Member

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    I have the pack off the 2007 Prius and I'm using a Vector 12V (2/4/6amp) charger. I have it on 2amps charging and am checking each module after 30 minutes. The problem is charging one module affects the module next to it. I am using a 12V battery-tester and after charging it read "recharge-retest" on the healthy module and the module next to it loses voltage/battery health.

    I tried searching for how to charge them but am only finding methods for more advanced-charging machines.

    1. should I take each individual module off and charge it so as not to affect the module next to it? this causes the module to swell and is not encouraged as its best to keep the module in the pack while charging.

    2. If I leave it in the pack what is the sequence to charge the modules that are bad/low? There are 8 modules aka 4 blocks on the right-side of this picture below that are bad (8modules/blocks 1-4...reading blocks as right to left). The rest are reading at 7.4 and above.


    [​IMG]

    [​IMG]
     
    #1 priuslyfe, Apr 22, 2026 at 8:58 PM
  2. PriusCamper

    PriusCamper Senior Member

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    Each module (28) is 8 volts... Each block of two modules (14) is 16 volts. With a 12volt charge you'll either be overcharging a module or undercharging a block and it won't work. You can either buy a charger that charges up to 8 volt range or a charger that charges to a 16 volt range or a charger that charges to a 250v range.
     
    #2 PriusCamper, Apr 22, 2026 at 9:03 PM
  3. priuslyfe

    priuslyfe Member

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    It did work for charging up a module that was at 6.5 to 8.1 in the middle of the pack. the module next to it remained at 7.5
     
    #3 priuslyfe, Apr 22, 2026 at 9:34 PM
  4. mr_guy_mann

    mr_guy_mann Senior Member

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    What's the history of this pack? Usually if a module is 1.0 to 1.5V (or more) lower than the others, then it has a FAILED cell. It will not recover.

    Also, "just" replacing bad module(s) can work but maybe 90%(?) of the time it will throw more codes within months - weeks or days.

    There are MANY threads in the forums about replacing battery modules - or "refurbishing" your pack.

    Those who have had better results discharge - charge cycle all the modules. Some use a "grid charger" system that can cycle the entire pack at one time. Other use RC hobby chargers that cycle individual modules.

    Posted via the PriusChat mobile app.
     
    #4 mr_guy_mann, Apr 22, 2026 at 11:08 PM
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  5. priuslyfe

    priuslyfe Member

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    there does seem to be a see-saw effect when I try to charge a module.

    I get what you are saying though, If I'm gonna have to buy an expensive charger I'd rather just buy an entire refurbished pack.

    What about directly hooking it up to a 12v battery that isn't fully charged. I think I have a battery that has a lower reading maybe 9-10volts that is off the car.

    BTW: the rest of the modules block 5 through 14 all have 7.4-8v. I have also read some other priuschat threads regarding this issue. Most are using better more accurate chargers. I'm just trying to rig this battery pack to work.

    I have a feeling I'll have to buy 8 modules are roughly equal in voltage to the remaining blocks.
     
    #5 priuslyfe, Apr 22, 2026 at 11:12 PM
    Last edited: Apr 22, 2026 at 11:29 PM
  6. PriusCamper

    PriusCamper Senior Member

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    You could wire all the modules up in parallel rather than series and charge all modules up to 8v at same time. It won't balance the back very well, but could be enough to get car running again.
     
    #6 PriusCamper, Apr 23, 2026 at 3:17 PM
    Last edited: Apr 23, 2026 at 8:34 PM
  7. priuslyfe

    priuslyfe Member

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    how would I go about doing that?

    I have a feeling if I can get the 8 bad modules to be OK once I put it back in the car and drive it might equalize. Of course they'll still be the weaker modules overall but it might work.

    I only need to get this Prius to working condition so I can either use it as a spare or it will be saleable with mentioned conditions. It already has 350k miles so I'm not expecting much.
     
    #7 priuslyfe, Apr 23, 2026 at 3:33 PM
  8. PriusCamper

    PriusCamper Senior Member

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    There's videos on Youtube... You simply connect all the positive terminals together into one wire and all the negative terminals together into one wire. Then connect both wires to the charger. As in you're going to have to remove all the nuts and bus bars.
     
    #8 PriusCamper, Apr 23, 2026 at 3:45 PM
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  9. priuslyfe

    priuslyfe Member

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    thanks will look it up.
     
    #9 priuslyfe, Apr 23, 2026 at 3:57 PM
  10. Brian1954

    Brian1954 Senior Member

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    When you connect all the positive terminals together with one wire and then use a different wire to connect all the negative terminals together, that is called wiring all the modules in parallel.

    When the modules are installed in the car, they are all connected in series, and the voltage of the battery pack is 202v or higher.
     
    #10 Brian1954, Apr 23, 2026 at 5:50 PM
  11. priuslyfe

    priuslyfe Member

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    i take after this you can slow charge by 2amps? just hook up the charger to one end and let it balance out.

    it seems like after some work today on the modules, it seems only two of the modules are reading as BAD or replace, the rest are either good or average. Actually, I think all are recoverable modules. thinking about charging it in series and installing it in the Prius and hopefully drive it to get it healthier.
     
    #11 priuslyfe, Apr 23, 2026 at 6:31 PM
  12. Brian1954

    Brian1954 Senior Member

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    I was pointing out to PriusCamper that what he wrote in post #6 was not correct

    What PriusCamper should have wrote in post #6 is: You could wire all the modules up in parrallel rather than series and charge all modules up to 8v at same time.
     
    #12 Brian1954, Apr 23, 2026 at 8:01 PM
    Last edited: Apr 23, 2026 at 8:13 PM
  13. priuslyfe

    priuslyfe Member

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    sorry I'm really confused. I found videos on how to wire up 12V batteries but couldnt find one for prius modules...how exactly would I do this?

    would i have to take them out of the pack and line them up on a table?
    do i have to do all or can I do half or less at the same time as it seems like each block might be able to be charged with only 2 modules?
     
    #13 priuslyfe, Apr 23, 2026 at 8:21 PM
  14. Brian1954

    Brian1954 Senior Member

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    I would advise that you should not charge the 28 modules with the 12v charge when they are wired in parallel. I would not use the 12v charger to charge any of the modules. If you want to do it correctly, buy the proper RC hobby charger.
     
    #14 Brian1954, Apr 23, 2026 at 8:27 PM
  15. PriusCamper

    PriusCamper Senior Member

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    Oops... Thanks for pointing that out. Was writing too fast again while watching Youtube. I just fixed it!
     
    #15 PriusCamper, Apr 23, 2026 at 8:35 PM
  16. PriusCamper

    PriusCamper Senior Member

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    Yea... That was the first thing I said in the conversation but they insisted and decided maybe they're so broke or cheap they can't afford any other option so went along with helping as best I could. But to your point this method is a band aid, or maybe less than a bandaid and might only get the car back on the road briefly. People have used this method on here in the past when they didn't have any other option but it'd be better to do it the right way.
     
    #16 PriusCamper, Apr 23, 2026 at 8:38 PM
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