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reconditioning discharge voltage

Discussion in 'Gen 2 Prius Main Forum' started by PriusOwner428, Apr 14, 2022.

  1. PriusOwner428

    PriusOwner428 Junior Member

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    Reconditioning battery pack one module at a time using a EV-Peak CQ3. Current question is to what voltage level should the modules be discharged? I've seen a kinds of numbers out there. Some saying not to go below 5V and others saying to go down to 3V. Interested in what others that have done this process think and why. I know the Prolong says to take them do to 3V:

    First Discharge: 134V / 28 = 4.8V
    Second Discharge: 101V / 28 = 3.6V
    Third Discharge: 84V / 28 = 3.0V
     
  2. PriusCamper

    PriusCamper Senior Member

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    I like to go down to at least 1 volt on the third round and when I first learned in 2018 Hybrid Automotive was saying you need to go down to 0.06v but that takes so long I use 12v 50w & 20w light bulbs to speed it up. It comes down to stress testing versus how many modules do you want to ruin before you put that pack back in... Thermal camera helps alot at finding bad cells too.
     
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  3. alftoy

    alftoy Senior Member

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    Which thermal camera are you using?
     
  4. PriusCamper

    PriusCamper Senior Member

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    Cheapest one with largest sensor...
     
  5. PriusOwner428

    PriusOwner428 Junior Member

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    Interesting. So Hybrid Auto/Prolong was saying 0.6V in 2018? I got that number from the Prolong website (Third Discharge: 84V / 28 = 3.0V). So in 4 years they drastically changed their recommendation. As far as ruining the modules, I assume if the modules were reasonably healthy they should be able to survive and improve from that deep plunge right? So what you're really doing is helping push those borderline "good" modules over the edge.
     
  6. PriusCamper

    PriusCamper Senior Member

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    Yeah... They raised that lowest number more than once. It's not easy selling a product like this to consumers who are going to yell at you if you kill their pack.

    The other aspect of this is that my buddy Joe in Oregon who has $30K in lab-grade battery rebuilding equipment with robust software never has to go below 6v in his three rounds of reconditioning and the reject modules he deems not good enough for the packs he rebuilds, but still good, are the ones I buy from him and they're always the strongest module in a pack I add them too.

    He thinks it's thoroughly amusing that he gets better results than us only going down to 6v and can't comprehend why we would waste so much time going so low and getting less favorable results.
     
  7. PriusOwner428

    PriusOwner428 Junior Member

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    Well that's easy to understand. We don't have 30K in equipment & years of experience. We're out here rubbing two sticks together.

    Since I've gotten module 2 to finally hit above 5000 on discharge & 8000 on the charge twice in a roll, you think module 2 has finally been recovered, or is still screwed? Doing discharge to 6V right now.
    upload_2022-4-15_21-22-17.png
     
  8. mr_guy_mann

    mr_guy_mann Senior Member

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    When I did my pack, if a module didn't have good capacity on a discharge after cycling down to 6.0V, there was nothing to lose (except time) by going down to 5.0V or 4.0V. Either a module improved to at least 5500mAh where the others are, or it's junk.

    Posted via the PriusChat mobile app.
     
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  9. TMR-JWAP

    TMR-JWAP Senior Member

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    You are misunderstanding how the prolong system works.
    You will NEVER see:

    First Discharge: 134V / 28 = 4.8V
    Second Discharge: 101V / 28 = 3.6V
    Third Discharge: 84V / 28 = 3.0V

    It will never happen because that's not how it works.
     
  10. PriusOwner428

    PriusOwner428 Junior Member

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    If I were using a Prolong to do the whole pack at once I would expect to be able to see:
    First Discharge: 134V
    Second Discharge: 101V
    Third Discharge: 84V

    Since I'm using the CQ3 & doing each module individually I would expect to be able to see:
    First Discharge: 4.8V
    Second Discharge: 3.6V
    Third Discharge: 3.0V

    What is wrong with my thinking?
     
  11. TMR-JWAP

    TMR-JWAP Senior Member

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  12. PriusOwner428

    PriusOwner428 Junior Member

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    OK thanks. That was interesting and informative. Ironically my best move when I first got this pack might have been to simply have installed it in the car to see if it triggered any codes. It might have been well balanced especially since all the individual modules were within .02V of each other. Now I might have improved all individual modules but also increased the delta between them.
     
  13. TMR-JWAP

    TMR-JWAP Senior Member

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    If the modules are "good", a bit of voltage difference between them won't cause a problem. They'll even out as the car is used. I have a thread in here somewhere in which I purposely repaired a battery by replacing a failed module with a module reading about 0.5 volts lower than the others. Worked just fine. The important thing is that it's a good module.
     
  14. alftoy

    alftoy Senior Member

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    Thanks, but I would have thought you would have sourced a reasonably priced one. Possibly one less than $300, maybe one you found on ebay. $300 is certainly a no go for just measuring cell temp. Which one are you using or is it just your buddy in Bend using one?

    Since the cameras are infrared, why not an infrared laser thermometer for $30.
     
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  15. PriusOwner428

    PriusOwner428 Junior Member

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    I guess that continues to be my problem. Figuring out what defines a good module. I thought a good module was one that when discharged would be at 5000mAh or higher & when charged could reach 7500 or better. Problem is even when I get those numbers, the next cycle could have them out of that range again. The whack-a-mole problem on an individual module level.
     
  16. alftoy

    alftoy Senior Member

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    Maybe load test each module to find good or bad module.

    Prolong Battery Module Load Tester User Guide | Hybrid Automotive

    Or make one yourself.
     

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    #16 alftoy, Apr 16, 2022
    Last edited: Apr 16, 2022
  17. TMR-JWAP

    TMR-JWAP Senior Member

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    If your measurements are that inconsistent, there is something wrong with your setup or the equipment you're using.
     
  18. PriusCamper

    PriusCamper Senior Member

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    Yea, I always try the cheapest solution first... Problem is there's 168 cells in a Prius pack and it was a total fail pulling the trigger on a cheap laser thermometer 168 times every time you want to check the whole pack compared to a quick glance at cheap thermal camera that color codes the hottest cells.

    The one I currently have is the cheapest Seek Thermal that plugs into your phone and is a bit over $100 because we bought it used on ebay... The flir works way better because it allows you to blend an image sensor with a thermal sensor. Here's a picture of what I'm talking about. These bad modules tested out fine by every other measure. But clearly they're about to fail due to heating up:

    Screenshot from 2022-04-16 16-10-01.png

    It's worth the money because there's lots of uses for these cameras if you're for example trying to make winter home heating more efficient, or sourcing an exhaust leak or optimizing cooling systems in your house, etc...
     
    #18 PriusCamper, Apr 16, 2022
    Last edited: Apr 16, 2022
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