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Reconditioning my Gen 2 battery and all cells have low capacity

Discussion in 'Gen 2 Prius Technical Discussion' started by bbellgrl, Jun 22, 2024.

  1. bbellgrl

    bbellgrl New Member

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    I am in the process of trying to recondition my 2008 Prius hybrid battery using a EV-Peak BGUAD CQ3 Multi Charger. I am new to this, and I have the charger set to do 5 discharge/charge cycles with discharge at 1 amp/6v and charge at 3 amps with capacity cutoff set to 7500 mAh.

    The results I'm getting are a bit weird. After running a minimum of five cycles on 12 cells, only 1 cell has reached a charge capacity of over 1000mAh, and none have reached a discharge capacity of over 1000mAh. They all test at least 7.8v, regardless of whether they have gone through the discharge/charge cycles yet.

    Here's an example of the first 5 discharge/charge cycles on 3 random cells:

    Cell 1: 694/627, 643/338, 337/160, 182/733, 676/460
    Cell 2: 647/121, 159/770, 748/832, 726/262, 289/122
    Cell 3: 665/231, 269/854, 790/854, 803/697, 682/804

    Is it weird that all my cells have such low capacities? Or is it common with an original battery pack on a 150k mile 2008? I am seeing improvement on many cells, but it's like from 550mAh to 685mAh. Never close to 1000mAh.

    Thanks for the help!
     
  2. dolj

    dolj Senior Member

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    What is your charging setup?
     
  3. ColoradoCrow

    ColoradoCrow Active Member

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    Age, Heat and time are all factors that reduce the life of the OEM NIMH batteries. 2024 is about correct timewise for an 2008 OEM battery to start dying.It sounds like you are doing everything correctly.Not sure what your rate of charge is but slow is key slow up and slow down. If you plan on keeping the car for 5 more years. I would side hustle with Amazon Flex or Grub Hub make $2,000 and buy a New Battery. This might not be an option for you. But those are low miles and a new battery will give you value both if you keep it or sell the car down the road.
     
    Danno5060 likes this.
  4. Tombukt2

    Tombukt2 Senior Member

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    Maybe now that you've seen a little bit about how this works and you're tearing into things and seeing more of how things work and get corroded and and so on and so forth is Prius really the car that you really need to make a big deal out of? You could be in the Yaris and get 5 mi to the gallon less gas mileage approximately that will take a long time to add up to the price of a battery the price of the coolant pumps and replacement parts that go on these cars so on and so forth. So unless you are packing on the miles making serious money doing Amazon flex and hauling old folks their food then maybe maybe and only a slight maybe is the Prius possibly right for your situation. Or you enjoy spending time rebuilding batteries and playing games and whack-a-mole and so on because you have plenty of time with the way work is going today you're not making your money off this kind of work it's just for enjoyment or I can't even imagine what. People with real jobs that have to go and have to perform generally wouldn't have time for Prius antics and games for the most part unless they making really good money at their job and they can just hand it to somebody and pay $3,000 back and have it handed back and they have a spare car when the Prius messes up so somebody who's sitting with an old Yaris and an old Prius they pretty much have it figured out and relatively cheaply too you can own an old Prius and an old Yaris for three payments of whatever you might be paying on or it is possible We do it here quite a bit.
     
  5. bbellgrl

    bbellgrl New Member

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    Thanks for the reply. This car belonged to my niece and when she bought a new car, the Prius sat outside in the AZ sun for almost 2 years without being used at all. We needed to replace the 12v, and then we got the car running briefly with the red triangle.

    I intent to get the car running and working without error and then sell it. I don't know what it's worth, and have considered just buying a refurbished hybrid pack to replace mine, but i don't know if that's even worth spending money on. If I can be relatively sure that the original pack can't be reconditioned, I guess I'll buy a refurbed one so at least the car has some value and can be sold, rather than be a piece of scrap.

    I guess I'm just trying to figure out if I'm doing something wrong, or if it's normal to have a full pack with all cells registering capacities under 900 ish.
     
  6. Tombukt2

    Tombukt2 Senior Member

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    You've got to be thinking to yourself or out loud a generation two or what have you Prius sitting 2 years unused out in the San Diego weather if that's the case what are you going to have after you recondition the battery and what might it be worth and there's always these things You can do a lot of things and still not have a lot of car left to sell just because of the age itself so there's always that people get to seeing dollar signs with an old car now because they're double what they used to cost so several years ago say 10 I used to buy these cars for $500 now people want 4,000 for them then again many don't get sold and I don't really know what happens to those nobody ever post what really happens they just say they want $6,000 and then they vanish many of these cars don't get sold or they get sold for less than half of what's asked or even less
     
  7. JON KIRKEGAARD

    JON KIRKEGAARD Junior Member

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    Screenshot 2024-06-22 115307.png

    I in the same boat with a 2008 currently and thinking about just doing the $1950.00 new batteries from Toyota at least they are new, and have a one warranty if I install 3yr if they do (I can't afford their labor rates).
     
    #7 JON KIRKEGAARD, Jun 23, 2024
    Last edited: Jun 23, 2024
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  8. Carall

    Carall Member

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    Apparently this is the case when the RC charger is useless. A grid charger is needed to restore the capacity in this battery, but this will most likely last for 2 years.
     
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  9. BrokenPipe

    BrokenPipe Junior Member

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  10. bbellgrl

    bbellgrl New Member

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    Thank you! This is precisely the information I was seeking. I will try these changes and see how things go, then report back here.
     
  11. TNToy

    TNToy Member

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    Hopefully the changes work. The issue is likely the length of time the vehicle sat with a fully depleted battery. Definitely use good 18 gauge cables and try cycling down to 5 volts with a 0.5A discharge and a slower 1 amp charge.

    The last battery I restored/rebuilt: 2005 with 207,000 miles. I bought it for $1,500 with a failed hybrid battery. Was not left to sit for any amount of time.

    3A charge to 7500mAh.
    2A discharge to 6.0 volts.

    Wound up replacing 3 modules with eBay units. (I chose to replace #7 in addition to the highlighted ones.)

    Prius Battery Restoration.jpg
     
  12. bbellgrl

    bbellgrl New Member

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    UPDATE: I ditched my cheap wires from Amazon and got ahold of some new banana plugs and alligator clips, then made my own 18awg wires. That did the trick, and now my numbers are much more normal. I'm hitting capacity (7500mAh on almost half of my cells, and the rest are in the 5500-6500 range.

    Weirdly, I'm not seeing any super weak cells, even though I see what looks like a pool of dried battery acid under the 5-6 cells on the far end on the metal frame.

    My results are shown here, but i'm not sure what to do about the cells that hit charge capacity in the first run with the discharge capacities in the 1500 - 2500mAH range. Do I need to keep cycling those until the discharge capacity gets closer to 5000mAH? Do you see any standout weak cells in my results?

    Is it recommended to clean up what I think is the acid from a leaked cell? Note that all my cells are testing well, so none looks to be weak enough to substantiate that leakage.

    IMG_1557.jpg Screen Shot 2024-07-01 at 12.59.06 PM.png
     
    #12 bbellgrl, Jul 1, 2024
    Last edited: Jul 1, 2024
  13. BrokenPipe

    BrokenPipe Junior Member

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    You can try to keep cycling, but it may or may not result in much improvement. How much time do you have to work on the pack? Personally I'd just ensure that every module was cycled atleast 3 times and then sort the modules from best to worst. Then obtain about 5 to10 used modules and test them yourself, ensuring they are better than any of the ones you will remove from the pack.
     
  14. bbellgrl

    bbellgrl New Member

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    Thanks for the reply. I kept cycling and ultimately got better numbers, and then posted a new thread here.

    Issue now is that essentially all modules except 2 were able to hit the 7500 discharge capacity (the other 2 made it to 7100, so still good). Problem is only 2 modules reached 5000 mAh on discharge. 24 are in the 4000 range (some low 4000s, some high 4000s), and 2 are at 3900. If I continue to run more cycles on these lower discharge modules, they always hit charge capacity at 7500 and then the cycle stops without ever seeing higher discharge numbers.