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NiMH Sensitivity D-Peak?

Discussion in 'Gen 2 Prius Technical Discussion' started by Houston Hybrids, Apr 17, 2014.

  1. Houston Hybrids

    Houston Hybrids Junior Member

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    If you use a Thunder T6 Multi, is there a suggested D. Peak value in mV? I have heard different theories, and I am ready for a good experiment :) This is for balancing a Gen II pack only btw.

    Jessica
     
  2. KhaPhoRa

    KhaPhoRa Member

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    Well I guess I have something new to test :) I've had mine set at 20mv, but of course I'm trying to really stretch out the balancing. Basically too low and you won't balance much (or at all) and too high and you could over charge if you're charge rate is too high. From my reading the general consensus is 6mv is a fair number. When I was doing the 400ma test charge delta peak never kicked in, but that could have been because I ran out of time on such a slow charge. I think I'll do another run and just leave it on for a day.. I get too antsy though.. I need strength!



    the Seahawks training facility ?
     
  3. Houston Hybrids

    Houston Hybrids Junior Member

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    Be strong my brother! I think the default is 7mV correct? What do you think about 20 mV with a charge rate of 3.5 mAh? My capacity cutoff is 7500mAh. Also, this 3.5mAh stuff is slower than molasses (or my Prius). I really want to push it back to 5.o, but I don't want to push my babies too hard. What do you think?

    One more thing. What do you think about having half of the batteries discharging while the other half are charging? This should reduce the amount of wattage for everything to run at onece, correct? I have had to run new lines to each battery because I noticed that they values were dropping each time I added a new battery to the line.... duh. It took me forever to figure out that the power company was pulling our electricity back by 10% during the day and effing up my end rates too. The batteries that charged at night looked great though, lol. Now we have a 20A line for each power supply and that seems to help...

    Jessica
     
  4. KhaPhoRa

    KhaPhoRa Member

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    Sounds good to me. Experiment with your setup. With the first charge I might drop that cutoff depending on what kind of numbers you're seeing on the initial discharge. I think you're doing great as is though, but there's always room for improvement :)

    If you have the means I would do a two stage charge, 5a then slow it down. while I still feel 3.5a is too fast for a safe balance charge I'm less worried after opening up one of theses modules. The individual cells seem very robust. Thick plates thick separators. Just keep an eye on heat. Btw have you ever put your ear to one after an aggressive charge? It sounds like rice crispies in milk for a long time after charging stops. It's eerie.

    depends on the charger. Some chargers can discharge back into a dc power source. Most of the hobby chargers including the thunders just discharge by sending the current through a resistive load generating heat (hence the 5 watt limit on the smaller ones) so that energy is "lost."
    I think it would be okay to do it that way, a 700mah discharge won't generate any heat you would have to worry about. It'll definitely be an efficient method time wise; I say go for it.
    I hope I get to see your setup!





    [​IMG]here is a view inside one cell.


    facility using
     
  5. Houston Hybrids

    Houston Hybrids Junior Member

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    Sweet- I will tinker around with things and let you know of the results asap. Awesome picture!
    Jessica
     
  6. KhaPhoRa

    KhaPhoRa Member

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    It would be painfully easy to drill a small hole and add some electrolyte (blue Gatorade?).. I have no idea if it'll help recover moderate cells or not.. Guess what? Testing time.
    Anyone know for sure if these cells use potassium hydroxide?



    the Seahawks training facility ?
     
  7. Houston Hybrids

    Houston Hybrids Junior Member

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    Now you sound like a mad scientist! Don't blow your self up dude.

    Jessica
     
  8. nh7o

    nh7o Off grid since 1980

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    Yes, according to Toyota:
    ESQ - Nickel Metal Hydride (NiMH)

    Keeps us posted. I think the idea of adding some electrolyte has merit. Is that rice crispy in milk sound due to bubbles rising?
     
  9. KhaPhoRa

    KhaPhoRa Member

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    I'll definitely let everyone know. I charged the cut open module tonight. This was a poor module with a capacity around 2000mah. With access to the individual cells I was able to watch individual voltages. The middle two cells peaked fairly quickly which makes sense seeing as they would be in the middle of the pack where heat will build up and therefore have lower potential capacity due to damage. As far as the popping it is likely oxygen / hydrogen recombination. As long as the charge rate is slow enough this can happen without pressure buildup. The cells aren't wet enough to support bubbling in the traditional sense.


    the Seahawks training facility ?
     
  10. Houston Hybrids

    Houston Hybrids Junior Member

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    I set a single module to 20mv for D-peak and everything went fine....then I tried a whole pack set at 20mv. That lasted about an hour until all the modules started blinking "NIMH FULL" over and over. Not sure what is going on here, but I put the d-peak back to default for now. Any ideas?

    Jessica
     
  11. KhaPhoRa

    KhaPhoRa Member

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    Sounds like D-peak did it's thing and shut down the charge.. With lower d-peak values it doesn't shut down like that? Did you also bump back up to 5a charge rate?


    the Seahawks training facility ?
     
  12. Houston Hybrids

    Houston Hybrids Junior Member

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    Ya, I bumped the charge rate back to 5a and set the d-peak to default. I guess it did the opposite of what I thought it would!
    Jessica
     
  13. Scott Caputo

    Scott Caputo Junior Member

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    I know this is a basic question, but I have been trying to seek and find the info myself to no avail.

    I picked up an 06 Prius and am going to attempt to recondition the battery pack. I already had a Thunder T6 charger that I used to charge drone batteries. I would like to find an AC power supply, as It only came with a fixed power supply cable for DC charging with alligator clips. I don’t think trying to charge these Prius cells from a car battery is the way to go, but I also couldn’t find much Info on that. Any advice on which power supply to get would be appreciated. Thanks
     
  14. R-P

    R-P Active Member

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    Any way you can use a carbattery with a carbattery-charger attached to it?

    My (fake) Imax B6 chargers car run of off a 20V max charger, so I can use a 19V laptop power supply. But yours seems to have a more limited range: It needs a 11-15V and >200W powersupply (according to quick search).

    But the 200W demand also depends on what you're doing with it. If you use the charger at the max of its ability, you need that 200W. But if you only charge two modules in series and with 1 ampere, then you only need (14V x 1A times 4 chargers = 56W, plus some extra for headroom and for the charger itself, so say) 70W.