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Acceptable Capacity...

Discussion in 'Gen 3 Prius Technical Discussion' started by dirt657, May 15, 2019.

  1. dirt657

    dirt657 Member

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    I’ve been reconditioning GEN 2’s on Craigslist for a lot of people in my area, and this last week I got a GEN 3 (prius C). The last 5 GEN 2’s I’ve gotten, using my Hobby chargers (4 turnigy Reaktor singles and 6 Prophet Sport Quads so I can charge 14 modules on 2 different batteries at once) I’ve only gotten 1 dead cell each time and all other 27 modules have been restored to 5A capacity or higher. With this gen 3, I’ve had not one single module read below 7 (in my experience the indication of a dead module), but only a few modules restore to 5A capacity or better...am I missing something? Below is the load tests I’ve done on each followed by the capacity results after 3-6 cycles each. (Correct me if I’m wrong but the C uses gen 3 modules)

    Module cap test Prius C
    20 7.97 7.41 .56 restored to 4400 mah

    19 7.87 7.40 .47 restored to 5100mah

    18 7.86 7.39 .47 Restored to 3500mah

    17 7.86 7.38 .48 restored to 3500 mah

    16 7.86 7.37 .49 restored to 3800mah

    15 7.86 7.35 .51 restored to 3400mah

    14 7.86 7.35 .51 restored to 1300 mah (dead)

    13 7.87 7.36 .51 restored to 1200mah (dead)

    12 7.88 7.36 .52 restored to 1600 mah (dead)

    11 7.87 7.37 .52 restored to 2200 mah

    10 7.87 7.29 .58 restored to 2400 mah

    9 7.87 7.35 .52 restored to 2800 mah

    8 7.87 7.35 .52 restored to 2750 mah

    7 7.86 7.36 .53 restored to 2400 mah

    6 7.86 7.36 .56 restored to 2500mah

    5 7.87 7.36 .51 restored to 3300 mah

    4 7.85 7.38 .47 restored to 3900mah

    3 7.86 -7.38 .42 restored to 4000mah

    2 7.86 7.43 .43 restored to 4800 mah

    1 7.86 7.43 7.43 restored to 5200 mah

    My questions are

    1. Is this a bad pack? It seems very low to me as far sensitive capacity.
    2. I hear gen 3 modules rarely drop to the 6’s or below like the Gen 2’s do. Why is that?
    3. If I put something with say 3500 mah capacity back in the pack, how long is it gonna last? What about 4000, 4500 or even 3000 mah?

    Gen 2’s seem so much more simple. I haven’t even had to load test the last 5 batteries because they all restore and it’s easy to find the dead cells. If anything doesn’t get up to 5000 mah, I don’t even put it in the pack.
     
    #1 dirt657, May 15, 2019
  2. Grit

    Grit Senior Member

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    o_O
     
    #2 Grit, May 15, 2019
  3. TMR-JWAP

    TMR-JWAP Senior Member

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    There's effectively no difference between a Gen 2 and a Gen 3 module.
    A bad internal cell is still a bad internal cell, whether it's old or new and it will drop the module voltage by ~1.4 volts.

    In the big picture, max capacity isn't as important as being well balanced. Every one of those 20 modules would be considered scrap if it were mine.

    And why are you doing 14 at a time on 2 different batteries? Cycling every other module? Why not make a test bench with a base plate that has a OEM cooling fan and ductwork to provide OEM cooling to the pack. Then you can do one full pack at a time.
     
    #3 TMR-JWAP, May 15, 2019
    Last edited: May 15, 2019
  4. dirt657

    dirt657 Member

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    I’m not much of a craftsman. I’ve been considering doing that but I’m not sure which way is the best way to go.
     
    #4 dirt657, May 16, 2019
  5. dirt657

    dirt657 Member

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    Also, what qualifies a module to be good to go for you?
    Also w
     
    #5 dirt657, May 16, 2019
  6. dirt657

    dirt657 Member

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    Speaking of which, I do make sure everything is balanced properly before buttoning everything up and putting it back in the car :)
     
    #6 dirt657, May 16, 2019
  7. wnrsm

    wnrsm Member

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    Have you measured capacity of the same module using both Turnigy and Prophet?

    My Prophet quad charger is showing >6800mAh capacity for some modules, which is higher than original/new. The Turnigy reports much lower numbers, which must be more accurate.

    I contacted HorizonHobby and asked about this accuracy. I was told two things:
    1) It is safe to discharge NiMH to zero volts.
    2) All that really matters is battery voltage.

    Here's their reply, pasted verbatim. I can't make this up.

    "We certainly appreciate you reaching out to product support. What matters is the voltage in almost all situations. If the battery is getting to the proper charge voltage and or discharge storage values.
    NiMAH batteries as you may already know, can go as low as 0.0v and still accept a charge. Values like the 'Percentage' or the 'Mah" values may be slightly skewed. The numbers that truly matter are the voltages.
    The voltage at the start of the charge, and the end of the charge. "
     
    #7 wnrsm, May 16, 2019
  8. TMR-JWAP

    TMR-JWAP Senior Member

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    That makes as much sense as standing on your head to take a leak...........

    But, you have to remember, they're referencing everything to an RC vehicle battery, not a HV battery module. I would be hesitant to follow any advice they provide. Probably would work great for your toys, but not so much for your Prius...
     
    #8 TMR-JWAP, May 16, 2019
  9. wnrsm

    wnrsm Member

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    Aha! So I can replace my Prius modules with RC batteries and be able to deep cycle them? Think of the weight savings when all I have care about is voltage! Just string together 168 AAA-size cells to get enough volts. That's way cheaper. You fools are doing it all wrong (sarcasm)

    In reality, they gave me dangerous advice (recharging NiMH from zero volts) and addressed my question about accuracy by (incorrectly) stating that it doesn't really matter. The charger you linked was cheaper than mine too. It is the exact same cheap guts with only a different color case. Here I thought I was avoiding the trap by avoiding the cheapest I could find. :-/ The best they could do to support me is replace it with another one of the same manufacturing tolerances and quality.
     
    #9 wnrsm, May 16, 2019
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