Load Testing and Balancing HV Battery Pack SKYRC iMAX B6AC V2

Discussion in 'Gen 2 Prius Main Forum' started by ElectricGreySquirrel, Apr 26, 2020.

  1. ElectricGreySquirrel

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    I'm in the process of repairing the HV battery on my 2007 Prius. I got the triangle of death a few weeks ago. This is the second time replacing bad modules in this pack, last time was two years ago. One module was bad this time, so it was replaced. When I hooked up the HV battery to the car everything was fine until I forced charged for ten seconds. After this time block 5 was overcharged and block 14 was undercharged (using torque app) throwing a P3015 code. I took out the battery and load tested each module for 30 seconds. Below are those results. from the furthest from the ECU to the nearest. Module 28 is suspicious. My question is, how do I bottom balance all of the modules to prevent P3*** codes from happening and my modules from overcharging. I am using a SKYRC iMAX B6AC V2 to charge and discharge. Which menu options and setup should I use to get an equal voltage across modules? What voltage should I charge to? I've tried charge cycling but the machine keeps turning off after the first charge cycle when I enter 3 charge cycles. Thank you for any expertise.

    1) 7.54--> 6.46
    2) 7.80 --> 6.63
    3) 7.73--> 6.57
    4) 7.79--> 6.61
    5) 7.80--> 6.60
    6) 7.82--> 6.62
    7) 7.66--> 6.48
    8) 7.82--> 6.60
    9) 7.80--> 6.58
    10) 7.80--> 6.58
    11) 7.83--> 6.62
    12) 7.77--> 6.56
    13) 7.79--> 6.58
    14) 7.77--> 6.56
    15) 7.81--> 6.60
    16) 7.63--> 6.44
    17) 7.81--> 6.60
    18) 7.80--> 6.59
    19) 7.77--> 6.58
    20) 7.88--> 6.79
    21) 7.82--> 6.61
    22) 7.81--> 6.57
    23) 7.78--> 6.60
    24) 7.80 --> 6.58
    25) 7.79 --> 6.60
    26) 7.82 --> 6.62
    27) 7.67--> 6.58
    28) 7.43--> 6.11
     
  2. PriusCamper

    PriusCamper Senior Member

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    Do you have the data from your previous work? It's really helpful to put all the data on the same spreadsheet so we can study all the details. Also doing the math and writing out the voltage loss for each module after load testing makes it easier for us to help with a quick glance. I do way too much of this math on my own packs and don't want to have to do it for yours too.

    But in general you're in that awkward stage where it's hard to tell exactly which modules are the worst with a low amp load test and way easier to tell when the pack is in the car under high amp loads and throwing codes. Dr. Prius can help with that if you can post screenshots...

    Also, discharging all modules down to deeper and deeper levels (5v, 3v, 1v) to recondition them to restore capacity from 50% to 96% will give you more data to find bad modules. Often the next module to fail will be one that discharges much faster than the other modules in the third round or earlier of discharging. What I do is set up 5 multi-testers, soon to be 7 multi-testers and race them against each other while discharging them with 12v lights and watch them side by side to find the weakest module.

    Also keep lots of fans blowing on everything, don't let anything get too hot, especially when recharging from the deepest discharge. And if you can get a thermal camera you can sometimes find cells that are running hotter than others so you know it's about to fail.

    Here's one of my spread sheets to give you sense of how I set them up:
     

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    #2 PriusCamper, Apr 26, 2020
    Last edited: Apr 26, 2020
  3. ElectricGreySquirrel

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    Thank you so much PriusCamper. I will post all the data once the battery is re-installed. I'm looking for answers on the best way to use the iMAX to level all the modules to an equal charge. Do you know the settings used on this device to do this and the procedure?
     
  4. dolj

    dolj Senior Member

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  5. TMR-JWAP

    TMR-JWAP Senior Member

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    So.....the car threw a P3015 code..."Block 5 becomes weak"...............but you don't suspect Block 5 to be a problem?

    Gen 2 module blocks start with Block 1 being the 2 modules furthest from the ECU. Block 14 being the 2 modules closest tot he ECU.

    Block 5 would be the 9th and 10th modules from the end.
     
  6. ElectricGreySquirrel

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    The modules were tested with a 100 amp battery load tester.

    I did suspect modules 9 and 10 to be bad based on the error code. This is why I tested them all again. The preliminary load testing showed those cells to be decent. I think it was the last module being low on charge that made modules 9 and 10 overcharge when I performed the force charge.

    I supplied these numbers because it's what I had and thought it might help. My question is not with the load testing of the batteries, but how to bottom charge them to the same state so they charge equally with the iMAX. I'm aware that based on the health of the module it will deplete at a different rate.
     
  7. PriusCamper

    PriusCamper Senior Member

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    Well, some people have wired the pack up in parallel, which means connecting all the positive terminals together and all the negative terminals together and then charging the pack the way you would normally charge a single module. But this is a huge amount of electrons you have to pump into the system in this configuration and the SKYRC chargers aren't designed to do that... But maybe if you charged it for long enough it'd work. But it will take a long time and you'll have to have lots of fans to keep everything cool.
     
  8. TMR-JWAP

    TMR-JWAP Senior Member

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    Charging 28 modules in parallel would be challenging. The 28 modules would divide the available current based on module internal resistance. In extreme cases, one module may get 50% of the current and another may get 1% or less. It's potentially a crazy situation.

    Just 2 or 3 in parallel can be a feat of frustration.
     
  9. TMR-JWAP

    TMR-JWAP Senior Member

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    So you put a 100 amp load for 30 seconds on each individual module? The voltages in your chart show the module voltage immediately prior to load application (7.6-7.8), and then on the right it shows module voltage immediately prior to removing the load, or immediately after removal of the load, or a few minutes after load removal once voltage recovers and steadies out?

    On another note, set your charger to discharge/charge mode. Discharge down to 5.8 volts at 1.5 amps (or 0.8 amps if a 5w model), have it wait about 20 minutes, then charge at 2 amps (or whatever you're comfortable with, I suppose) with a max charge of 8200mah. You should be able to just keep whatever default delta is in the setup for detecting when fully charged. When the charge cycle ends, you'll be able to see total mah discharged and total charged back in. If the module is healthy, the discharged number should rise each cycle up until max improvement.

    If that's a single channel charger, it's going to take about a month or so (at 24/7) to get through 3+ cycles of 28 modules. I suppose it could be faster if you drain them at 100 amps (or x amps) and then charge them at 5 amps with the charger, but that kind of defeats the purpose of obtaining discharge measurements so you can actually see true module capacities.
     
    #9 TMR-JWAP, Apr 27, 2020
    Last edited: Apr 27, 2020
  10. ElectricGreySquirrel

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