Grid Charging HV Battery, voltage too high?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by '04Prius, Dec 20, 2020.

  1. '04Prius

    '04Prius Junior Member

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    Hey everyone,

    I just finished replacing some dead/weak modules in my traction battery pack. I tested all the modules with a H4 headlight bulb, and measured starting and ending voltage. I reassembled the car with used modules, and performed the battery reconditioning process with a Prolong grid charger and light bulb discharger. However, when the battery was supposedly in the “balance phase” it charged up to 249 volts, which is a decent bit higher than the 235-240 volts the website says the battery would have settled at. Any idea what would cause this? Is it a sign of other bad modules?

    Thanks
     
    #1 '04Prius, Dec 20, 2020
  2. SFO

    SFO Senior Member

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    The HA website voltage range is just for reference. You are fine at 249v.

    How many hours have you balanced this round?

    How many miles on the vehicle?
     
    #2 SFO, Dec 21, 2020
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  3. '04Prius

    '04Prius Junior Member

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    195,000 miles. I let it charge/balance for about 30 hours. After letting it rest for an hour, and trying to drive it, it’s pretty clear that there’s a failed module that I must have missed somehow. I guess it’s coming apart again tomorrow...
     
    #3 '04Prius, Dec 21, 2020
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  4. john1701a

    john1701a Prius Guru

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    My household voltage is 243 and that's what we've been charging the 2 plug-in Prius for years. So, I would also think your rebalancing at 249 would be fine.
     
    #4 john1701a, Dec 21, 2020
  5. vvillovv

    vvillovv Senior Member

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    Some other clues are voltage range at top SOC and bottom SOC in the car.
    After you let it rest for an hour what was the voltage?

    The voltage should drop fairly quickly from the top of the balancing phase or as some call it the "topping zone" or soak charge. Letting the pack rest after the balance phase and monitor the voltage drop until it slows.

    Also, don't be afraid to discharge the pack to it's nominal voltage, than monitor it's rebound voltage as it rises back up again, before installing it back in the car. It's just one other method you can try - because sometimes the car doesn't behave well if the pack voltage is too high and SOC gets too far out of spec.
     
    #5 vvillovv, Dec 21, 2020
  6. '04Prius

    '04Prius Junior Member

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    After resting for an hour the pack was at 233.5V. However the voltage of block 13 was a lot lower than the rest of them. I pulled the battery back out of the car, and it one of the modules (25 as I have it numbered, starting furthest from the computers) was at 7.3v, while the rest were all around 8.4. I pulled the battery from the car, and I’m going to re-load test all the modules. My guess is that one was weak, and the reconditioning process caused it to fail completely.
     
    #6 '04Prius, Dec 21, 2020
  7. vvillovv

    vvillovv Senior Member

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    My goal in replying to your thread is to encourage you with your pack reconditioning project.
    I have a few reservations beyond the low voltage #25 module of the #13 pair as stated above.
    Don't let my comments stop you from continuing your plan of action, as replacing #25 is a good plan in my opinion too.

    Since you are using Ely's Prolong grid charger, I'd give Hybrid Automotives tech support line a call and run your 249 volt - end of balance phase number by him and ask what he thinks. According to my Genesis One grid chargers Prius Gen 2 Profile shows absolute top end voltage for the packs 202 volt nominal voltage rating is 240 volts. Meaning at 240 volts the Genesis One will shut off completely.

    Another option if you think it might be helpful is to contact Jeff and Max Volts and inquire about one or a few of his reconditioned Prius modules for sale
    Used Toyota Prismatic Module– Maxx Volts
    and run the 249 volt pack top end by him for his take on the issue.

    iirc: I think it was Jeff during a chat in another forum that mentioned seeing much higher voltages getting pumped into some packs than the original final shut down voltages mentioned above - 240 volts..

    Believe you me - I know how steep the learning curve is with grid charging packs and how long it can take to untangle all the different takes on what is beneficial and what is non sense. - So I always try my best to let anyone I'm sharing my opinions with, that if I make any sense to you personally with my experiences and suggestions that is great, but if not that is also OK, as I don't know all the answers yet either.
     
    #7 vvillovv, Dec 21, 2020
    Last edited: Dec 21, 2020
  8. '04Prius

    '04Prius Junior Member

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    I ended up replacing module 25 today and reinstalling the pack in the car. I have it on the prolong charger now, and I’m going to let it charge/balance overnight. I load tested all the modules, and module 25, while it had a resting voltage of around 7.3V immediately dropped to less than 1V when a load was applied (could not even light the H4 headlight bulb) so it definitely needed replaced. I’m assuming that module had high impedance or something that raised the voltage of the entire pack (although I don’t really understand all the failure modes of NIMH cells). I found some mention on other threads in this forum about the voltage being high when a bad cell/module was installed in the pack. I’m hoping the new module solves the issue. I’m gonna keep an eye on the charger over the next few hours to see what voltage it stabilizes at. It’s currently at 233V. I plan to let it run overnight to balance the pack.
     
    #8 '04Prius, Dec 21, 2020
  9. '04Prius

    '04Prius Junior Member

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    So that apparently was not the case. The prolong charger reached 245 volts, and I shut it off, not wanting to potentially cause damage by charging the pack at too high a voltage. I charged the replacement module to a similar-ish level to the others with an RC car charger, and I’m going to let the car sit overnight and bleed off any heat that may have been generated. I’ll try driving it in the morning and monitor the voltage of the blocks using a scan tool.
     
    #9 '04Prius, Dec 21, 2020
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  10. '04Prius

    '04Prius Junior Member

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    vvillovv, I think I'm going to take your suggestion and reach out to prolong tomorrow. I don't understand enough about the way the charger works to narrow it down to an issue with my battery pack, or a potential issue with the charger.

    Just in case anyone is curious, here are the results of my load testing. I connected an H4 headlight bulb to each module for 120 seconds. The second reading was taken before switching off the load. There are some modules that are weaker than others, but nothing that stood out as needing immediate replacement. Module 1 is the module furthest from the ECUs. I did not try to rearrange the cells to match internal resistance. The one labeled "replace" is the used module that I replaced module 25 with. The lower starting voltage is due to a lower charge level than the rest of the cells already in the pack. I was a little hesitant to charge it not installed, since I had read about the modules swelling when charged outside the clamping force of the chassis.

    Module, Starting Voltage, Ending Voltage
    1 8.47 7.87
    2 8.46 7.92
    3 8.47 7.99
    4 8.39 7.96
    5 8.47 7.97
    6 8.45 7.96
    7 8.47 7.98
    8 8.45 7.96
    9 8.47 7.98
    10 8.38 7.95
    11 8.45 7.98
    12 8.48 7.92
    13 8.45 7.95
    14 8.41 7.88
    15 8.46 7.98
    16 8.45 7.93
    17 8.43 7.89
    18 8.45 7.91
    19 8.41 7.93
    20 8.45 7.96
    21 8.46 7.98
    22 8.47 7.9
    23 8.46 7.97
    24 8.46 7.96
    25 7.08
    26 8.39 7.79
    27 8.44 7.96
    28 8.44 7.97
    Replace 8.18 7.75
     
    #10 '04Prius, Dec 21, 2020
  11. dolj

    dolj Senior Member

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    Try this:


    Module Starting Voltage Ending Voltage Difference
    1 1 8.47 7.87 0.60
    2 2 8.46 7.92 0.54
    3 3 8.47 7.99 0.48
    4 4 8.39 7.96 0.43
    5 5 8.47 7.97 0.50
    6 6 8.45 7.96 0.49
    7 7 8.47 7.98 0.49
    8 8 8.45 7.96 0.49
    9 9 8.47 7.98 0.49
    10 10 8.38 7.95 0.43
    11 11 8.45 7.98 0.47
    12 12 8.48 7.92 0.56
    13 13 8.45 7.95 0.50
    14 14 8.41 7.88 0.53
    15 15 8.46 7.98 0.48
    16 16 8.45 7.93 0.52
    17 17 8.43 7.89 0.54
    18 18 8.45 7.91 0.54
    19 19 8.41 7.93 0.48
    20 20 8.45 7.96 0.49
    21 21 8.46 7.98 0.48
    22 22 8.47 7.90 0.57
    23 23 8.46 7.97 0.49
    24 24 8.46 7.96 0.50
    25 25 7.08
    26 26 8.39 7.79 0.60
    27 27 8.44 7.96 0.48
    28 28 8.44 7.97 0.47
    29 Replace 8.18 7.75 0.43
     
    #11 dolj, Dec 22, 2020
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  12. vvillovv

    vvillovv Senior Member

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    It’s currently at 233V. I plan to let it run overnight to balance the pack.
    #8' 04Prius, Yesterday at 9:20 PM

    The prolong charger reached 245 volts,
    #9' 04Prius, Yesterday at 10:22 PM

    If the timestamps of your posts indicate how long it took to charge the pack from 233V - 245V
    It should take several hours for the charger to raise the pack voltage that much.
    Important numbers to keep track of when charging are:
    Start Time
    Start Voltage
    End Time
    End Voltage
    Module Temps
    Important numbers to keep track of during Discharge
    Start Time
    Start Voltage
    End Time
    End Voltage
    Module Temps
    Voltage Reads - at any set interval you choose
    (the more often you check discharge voltage the better)

    I didn't want to post anything yesterday until you had a chance to test the pack with the replaced module while driving the car today and or talk with Hybrid Automotive.
     
    #12 vvillovv, Dec 22, 2020
  13. '04Prius

    '04Prius Junior Member

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    I believe that one of the replacement modules was bad, and I must have missed it with my load test. Monitoring the block voltages showed that it was still block 18 that was fluctuating. Since I need the car to be reliable, I decided to just replace the entire pack with the 2k1toasterpack. Hopefully should have that installed by tomorrow.
     
    #13 '04Prius, Jan 5, 2021
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  14. vvillovv

    vvillovv Senior Member

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    It's always nice to have a spare pack. I have 3 that fit my older (other) hybrid.
    One of these summers I'm going to have to break them apart and try matching modules. But, I've heard too many stories about the wack a mole syndrome to want to do it before I absolutely have to.
     
    #14 vvillovv, Jan 6, 2021
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