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Lower voltage modules - do you try to recondition these or just replace?

Discussion in 'Gen 2 Prius Technical Discussion' started by Rocinante, Feb 18, 2023.

  1. Rocinante

    Rocinante Junior Member

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    I'm about halfway through the process of reconditioning my battery pack. I have 4 modules that had voltage issues in Dr. Prius, and then again when I checked them manually. You can see in the screenshot.

    The one that is ~1.20v below the rest, I didn't bother trying.

    The other ones aren't that far off. I know there is more to it than just checking the voltage, but when you see modules like this, do you even bother charging/discharging them, or would you just replace them?

    I ordered 5 replacement modules for now.

    Thanks.
     

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  2. BrokenPipe

    BrokenPipe Junior Member

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    Might as well try to revive them by doing multiple discharge / charge cycles. Sometimes they might go back to useable but not likely. In theory discharging to a low voltage might help. So you can start with 6 volt minimum discharge voltage on a hobby charger. Then see the amp hours the module accepts during a charge to full. If no improvement, keep dropping the lower discharge voltages and check for any improvement in amp hour capacity. I reconditioned a pack and noted the worst 5 modules in terms of amperage capacity and replaced with other used modules that had higher amp capacity. Once the bad modules were replaced, then used internal resistance measurements to pair up the modules so each pair had approximately the same total internal resistance. Then did a balance charge for 24 hours.
     
    Rocinante likes this.
  3. priusrecon

    priusrecon Member

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    Second the above....
    You got nothing to lose by trying a few charge/discharge routines on modules showing lower capacities.
    If they test good, you can use them.....but don't skimp, either on the reconditioning or the testing.
    My modules have lasted over 6 years now.
    Do full top offs between each, with discharges between each down to 50% voltage, then down to 25%, then lastly to less than a volt.
    Finish off with a nice long topping off again. Then test the hell out of it. I did three complete repetitions of the above.
    Adding brand new full strength blades into a pack of weaker ones can bring in it's own problems.
    One note - the amount the thing accepts during the charging phase isn't as important as the amount it can discharge, focus on the latter.
     
  4. Rocinante

    Rocinante Junior Member

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    What charger/discharger do you use?
     
  5. BrokenPipe

    BrokenPipe Junior Member

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    I used a ProTek R/C "Prodigy 610 QUAD AC" LiHV/LiPo/LiFe/NiMH AC/DC Battery Charger. There's a lot of settings and options in the menu so you can customize it to your needs. It did a good job reconditioning the modules. It didn't come with the cables, so ended up buying the connectors I needed and building them with wires.
     
  6. sam spade 2

    sam spade 2 Senior Member

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    Not likely indeed.

    Trying to "recondition" worn out batteries is an exercise in futility, no matter what technique you use.

    Most everybody who tries it eventually comes to that conclusion.
     
    BiomedO1 likes this.
  7. BiomedO1

    BiomedO1 Senior Member

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    Some people think that getting the voltage of the battery back up - the battery is good. That's far from the truth. If the battery can't handle an electrical load, it's useless. It's the same as a 12 VDC car battery that reads 12 VDC on a meter but can't start a car. How does it help the other batteries in you pack drive the electric motors in your transmission?

    Just my 2 cents....
     
  8. BrokenPipe

    BrokenPipe Junior Member

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    Reconditioning is definitely worth it. If the Prius is being driven constantly, and not just sitting around for months on end without being started, then there will likely be only one bad module in the pack. The battery ECU will immediately detect the bad module which has a lower voltage than the rest. So, if that one bad module is quickly isolated and removed from the pack, the reconditioned pack will serve a long useful life. It just makes sense not to scrap a whole battery pack due to one bad module.
     
  9. sam spade 2

    sam spade 2 Senior Member

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    The experience of MANY users......and the opinion of actual battery experts......is in direct opposition to everything you just said.

    IF.....you wait until one of more cells is really BAD, it is too late for any useful "reconditioning".
     
  10. Rocinante

    Rocinante Junior Member

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    Well my 7.99v module did go from 1771mAh to 4634 after a few cycles. It was getting some whacky readings in Dr. Prius last time I had the battery in the car but I'm going to use it and see what happens.