Gen 2 Battery Reconditioning Issues

Discussion in 'Gen 2 Prius Technical Discussion' started by stagermx317, Nov 4, 2021.

  1. stagermx317

    stagermx317 New Member

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    Hey everyone, I'm a prius DIY newbie, but a decent overall mechanic. I just recently returned from a 6 month deployment overseas and my 2006 prius had the red triangle come on for my wife about 2 months ago. I started watching the YouTube videos of how to recondition the battery with a hobby charger. The car has 275K on it, not sure if its the original HV battery, as we bought it used in 2017 with 189K on the clock.

    I ordered the bluetooth OBD2 sensor to hook up to the Dr. Prius App, but it didn't arrive before I pulled the battery, my voltmeter indicated that my cells were all in the 8.3-8.4 range with the exception of the cell #21 which was at 7.62. After reading further it seems that it would still be within spec, but regardless I purchased a new cell from Ebay.

    I pulled the battery and hooked up the cells to a hobby charger I purchased ( Lectron Pro ACDC Quad charger) and used the settings recommended by Gregg on his YouTube video
    (
    ):

    1. NiMh battery
    2. Discharge to Charge cycle
    3. 3-5 cycles
    4. Charge @ 3 Amps
    5. Discharge @ 1 Amp
    6. Capacity cut off @ 7500 MaH
    7. Safety timer cut off @ 720 min
    8. Temp cut off @ 176 degrees
    9. Wait time between charges 5 min

    My initial discharge on cycle one on all the cells ranged between 4800 and 5200 MaHs but after that, the charge and discharge cycles all dropped significantly, down to 1,000, 100s, or even 40 MaH. Having this happen to every cell has me wondering if I messed up one of the charger settings that were not covered in the video. Anybody have any experience with this or recommendations? Have I made my battery cells worse?
    Thanks for any help or suggestions!
     
  2. stagermx317

    stagermx317 New Member

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    Upon further review, i failed to edit one of the charger default settings. During the Discharge to Charge cycle, it discharged the batteries down to .1 volts. Reading some other posts it seems that this will damage the battery going below 6V, am I screwed or is there a way to bring them back to life?
     
  3. mr_guy_mann

    mr_guy_mann Senior Member

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    Don't know- might just try charging them at say 1A to 8000mAh and see what they look like afterwards with a 2 minute load test using a couple headlight bulbs. (Record voltage before, then at 120sec right before removing load)

    I assume that you have had all the battery modules clamped tight in the mounting frame and constantly cooled the whole time?
    Posted via the PriusChat mobile app.
     
    #3 mr_guy_mann, Nov 7, 2021
    Last edited: Nov 7, 2021
  4. stagermx317

    stagermx317 New Member

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    Yes I had the batteries clamped in the pack the whole time, I never noticed any of them bulging or getting hot. Im not an expert on internal battery composition, I have just heard that if they discharge below 6V that it is bad for them. I will try to the headlight test next, but when i put my charger on 1 amp, it only stays on for a few mins until it says the battery is fully charged with a few additional mAh added if any. I don't know how to set it to see what the total mAh reading is.
     
  5. mr_guy_mann

    mr_guy_mann Senior Member

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    Don't know about your charger, but I had to disable deltaV on mine, so that it would charge the "full" amount that I wanted. Could be that your modules are damaged already, but might well try.

    On some of my low capacity modules (that didn't show capacity increase at discharge to 6.5 to 6.0V) I went more aggressive on the discharge down to 5.0V (next cycle to 4.0V if needed) then 7500 to 8000mAh charge. Most modules improved but a few didn't and were replaced.

    Posted via the PriusChat mobile app.
     
    #5 mr_guy_mann, Nov 8, 2021
    Last edited: Nov 8, 2021
  6. stagermx317

    stagermx317 New Member

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    My charger manual says that the default delta-peak sensitivity is 7mv/cell. There is no off option, but I can change it from 5mv/cell to 20mv/ cell. How high of a setting do I know is safe to use?
     
  7. mr_guy_mann

    mr_guy_mann Senior Member

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    Well, my understanding of the process is that you are trying to "gently" overcharge the module- the cells that reach capacity first then convert power into heat while the others continue to charge. So I didn't want the charger to stop because it "thought" that the battery was full. Supposedly going completely full to completely empty helps "rearrange" the internal crystal structures or so such. Don't know what setting on your charger will let you accomplish that without kicking out.

    Lots of different opinions about charging rates and values, as well as discharge targets. Some say 1.5A charge, some say 0.5A. Generally slower is better for the battery but takes more time.

    Posted via the PriusChat mobile app.
     
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