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Battery Reconditioning Guidance

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Gino Veltri, Aug 8, 2022.

  1. Gino Veltri

    Gino Veltri Member

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    Ok so Ive been reconditioning my own packs and friends for a while now. And I know there is something key that Im not getting. About 1 out of every 10 packs I do, has a failed module within the first month.

    I charge the whole pack, one module at a time, at 2 amps until the charger decides that it is full, sometime reaching 8.6 volts. Let it sit for 20 min. Then discharge (at 2 amps, the max i can) to 6 volts or sometimes less if i think the module needs it. Let it sit 20 min. Rinse and repeat 2-3 times. My 3rd round of discharging doesn't always show improved numbers like the 2nd round does (red flag #1). I call these discharge readings "capacity", not sure how correct that is.

    I "load test" full modules by connecting 2 headlight bulbs and counting how long it takes to reach 7.5 volts. comparing the modules to each other tells me which are shot, sometimes.

    Im by no means a professional but Id love to learn what it is i dont know. Is my 2 amp charge rate to aggressive?
     
  2. edthefox5

    edthefox5 Senior Member

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    There all extremely old battery’s. How many battery’s have you seen last 15 years fail then you can do a couple of discharges and still work?

    Its just temporary at best. Those that last the longest are the ones driven the most the battery’s stay energized. Leta rebuilt pack sit all the time it’s going to fail fastest.
     
  3. Gino Veltri

    Gino Veltri Member

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    Fairly good point. 3 of my packs are donors that sat for years....I remember once seeing one of you nerds had taken it upon yourself to manufacture brand new NiMi modules. Cant seem to find it anymore tho.
     
  4. TMR-JWAP

    TMR-JWAP Senior Member

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    The first sentence is a problem. You're charging the modules prior to letting them tell you where a problem is located. Let the modules help you. Always do a discharge first, so you can see how much energy (mah) remains in the module when it's in the 'as removed from the car' state. Even better if it's been removed for a while, as you can more easily see if a module has a high self discharge rate. It's very easy to see modules that have low capacity when you do a discharge first. For example....If you end up with 25 modules that discharge 3000-3400 mah, one that discharges 700 mah, 1 that discharges 1200 mah and 1 that discharges 1700 mah, you already know which ones are more likely going to be problems, and which ones are still pretty well balanced. Sometimes they will recover very well after being cycled, sometimes not. Sometimes you may want to just toss those three and replace them with ones that you know are good from previous testing.

    If the first thing you do is charge them, you lose that data and can never get it back. Charging first can hide a lot of problems. Even after I cycle a pack, I let the modules sit for at least a month before using them, just to be sure there are no self discharge problems. My battery packs are bullet proof.

    A 2 amp charge rate is NOT too aggressive. It's exactly what I use. I mount 28 modules on a Gen 2 base (mounted and clamped just like OEM) and have an OEM cooling fan and ductwork connected to the bottom plenum for air flow. I have a Prolong kit set up on the bench just to run the fan. I have (10) 4 channel charger/dischargers available, so I can do all 28 modules at the same time.
     
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  5. alftoy

    alftoy Senior Member

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    Even if the pack has been sitting for 18-24 months, still discharge first?
     
  6. Gino Veltri

    Gino Veltri Member

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    Agreed letting them sit for an extended period really pinpoints the problem modules. But i usually dont work on a battery just pulled from a car. Wouldnt a headlight "load test" help pinpoint problems too? Of course "weak modules" are not the only problem a pack can have.

    For instance, working with the limited number of chargers i have, it is hard to get all the modules at the same voltage at the same time. By the time ive finished half the pack (discharging to 7.whatever) , the other half of the pack has rebounded above the other. Thus I have to let them sit for a long time to approximate equal, then fine tune the voltages to make the prius brain happy. What do you do? Or do you have the ability to do all modules at the same time?

    Also what are you using to clamp them during charging? Ive tried everything, but nothing prevents ballooning like the actual compression bars from the pack.
     
  7. Gino Veltri

    Gino Veltri Member

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    Also any tried and true level for delta sensitivity?
     
  8. TMR-JWAP

    TMR-JWAP Senior Member

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    When I get an HV battery, I disassemble all the support systems from it and install the clamped modules onto my test base. I do not remove the modules from the OEM clamp. The very first step I perform is to record all serial numbers and current voltage of each module. Then I connect all the test cables to the terminals. All my chargers are setup to do discharge/charge cycles. I ALWAYS do a discharge first. I've had battery packs that sat on a salvage yard shelf for 6 years. Discharge first. Discharge setpoint is 5.8 volts and 1.5 amps. It may immediately trigger the 5.8 setpoint, no big deal. Then it waits 20 minutes and starts the charge portion of the cycle. All my equipment uses the same program. I have a routine and I stick with it. Every module gets the same setup.
     
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  9. TMR-JWAP

    TMR-JWAP Senior Member

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    Pretty sure mine are set to 20. Eliminates just about all false triggers.
     
  10. JohnPrius3005

    JohnPrius3005 Active Member

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    Hi TMR-JWAP, Sounds good. Having a well thought out and standardized procedure, as well as sufficient equipment, seems like the way to the most likely success and avoidance of having to redo things.

    Would you mind sharing what chargers and dischargers you use? And are they capable of outputting data to graph results? I'm trying to learn as much as I possibly can and minimize the time spent on trial and error. Thanks in advance.

    Aloha. John
     
  11. Gino Veltri

    Gino Veltri Member

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    Normally Im all about trial and error learning. But how do you get the voltages close to each other? Also , how come .2 voltages apart doesnt set off the red triangle for me? Still i know they should be as close as possible and i dont think connecting all the positives and all the negatives together does much good for this.
     
  12. alftoy

    alftoy Senior Member

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    Hybrid battery balancing | Page 3 | PriusChat
    Cycling battery modules - do these results make sense? | PriusChat
    Cell Module health and rehabilitation | PriusChat
     
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  13. JohnPrius3005

    JohnPrius3005 Active Member

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    Thanx Alf!! Aloha.John
     
  14. tungm

    tungm Junior Member

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    Hello TMR-JWAP, thank you for sharing your wealth of knowledge. I have a 2014 Toyota Aqua (Prius C). It recently started throwing the hybrid battery error, each time I reset with Dr Prius app it runs normally for a week or so. But when I happen to have a prolonged EV event it's as if the ECU forgets to start ICE until battery SOC goes too low. Delta SOC and Delta V is never suspect until this even happens. Battery health is around 51% as per Hybrid assistant.
    -Could this be a symptom of something that's not the HV battery?
    -I just recently got a CQ3 4 channel charger and was wondering if it's possible to charge two modules per channel( the number of supported cells(15) got me thinking if I can speed up the process this way but have not seen anyone suggesting this procedure on the forum)?

    Thank you in advance.
     
  15. TMR-JWAP

    TMR-JWAP Senior Member

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    The charger can handle doing two series connected modules on each channel. It will save some time, but only on the charge side of the cycle. The charger will still be limited by it's 10 watt heat dissipation capacity on discharging. You could do this and use the capacity information to narrow down which module set(s) is weak and then do single modules if needed to determine the exact module that is weak.
     
  16. tungm

    tungm Junior Member

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    Thank you for the reply, and for confirming that detail.