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Re-hydrating the battery modules.

Discussion in 'Gen 2 Prius Technical Discussion' started by Britprius, May 6, 2015.

  1. Shaked4040

    Shaked4040 New Member

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    image.jpeg Hello everyone, thank you for the helpfull information youre uploading here
    I have a 2007 genII prius i bught last november with 248Kkm in a not so good condition for an almost fair price, maybe i will write more about it in another thread
    After seeing probably much less than avarage performence from the battery the red triangle lit up about a month ago with high voltage on module 7, i kept resetting and driving for about a wek or two till i thought thats enough
    Took the battery out and measured the modules, 5 were in lower voltage than the avarage (~7.6x vs 7.8x) and module 13 was 6.5, probably toasted with an inverted cell...
    Ive started a very slow process of balancing, with 1a/1a current 6v min, one at a time since i only have 1 imax charger (another 12 are on the way from china) giving more attention to the weaker modules (some discharged less than 1k) highest module discharged so far was about 4k
    Israel is a very hot country and i suspect that most if not all of them had seen 10 too much hot summers

    Figuring i dont have much to lose, im going for the rehydration
    My thoughts after reading all of the threads here:

    10% Naoh solution as hot as possible (this is what i have avialable)
    +
    1 weak capacity module

    About the process, im thinking of keeping the batteries in the pack

    Hole for each cell
    Instead of drilling a hole im gonna try and puncture with a needle, the same needle will inject the stuff into each cell
    The amount injected to each cell will vary according to its fullness state.

    Im going to attach the needle and one of the terminals to a voltmeter in conductivity/dcV mode and stop when solution level reaches the end the needle
    The needle is 20 mm total so ive installed a device which makes it shorter, about 15mm, which should be about 3 mm above plates

    Then im gonna cycle it to see changes
    Later seal it, probably
    What do you like/dislike about this methood?
    Both in leak preventing wise,
    Charging tips,
    Other stuff i should take into consideration,
    Your thoghts about life, love and other stuff...
    :)

    Shaked
     
  2. Britprius

    Britprius Senior Member

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    Hi Shaked.
    I think you will have trouble trying to make holes with a needle. The plastic tops are quite tough and thick. Why not use a drill the same size as the needle.

    Injecting hot solution will achieve very little as the amount of liquid needed is very small and the mass of metal inside the cells is high. I found that charging continuously at about 5 amps after filling will heat the cells once charged without damaging them. Charging without sealing the cells will prevent pressure build up.

    Good luck with this, but you have nothing to loose. I have had good results with many modules, but some will inevitably fail.

    I no longer have a Prius, but now have a Lexus GS450H with the same modules as the Prius, but 40 of them in the battery instead of 28.

    John
     
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  3. bisco

    bisco cookie crumbler

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    we miss you john, all the best with the lexus!(y)
     
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  4. Britprius

    Britprius Senior Member

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    Thanks Bisco.
    I do from time to time drop in, and see whats happening here adding what I can to the subjects.

    The Lexus although not as frugal as the Prius seems to be as reliable, and is returning the low 40's mpg UK gallons. Not bad for 3.5 Ltrs 296 HP, and 186 HP from the electric motor. The performance is something else with zero to 62 mph in 5.2 seconds in a car that weighs 2 tons.

    All the best to all my friends on PC, and I will continue to drop in when I can.

    P_20170316_155334.jpg P_20170316_155355.jpg P_20170316_161643.jpg

    John (Britprius)
     
    #284 Britprius, May 12, 2017
    Last edited: May 12, 2017
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  5. Shaked4040

    Shaked4040 New Member

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    Beautyfull car
    Rhank you for your assitance
    I have a question
    How low car i dischargre a module?
    In all threads in prius chat i see that minimum is 6.0, somtimes 5.7
    Just in this therad i see people write its possible to go down to 3V!?
    I what conditions and circumstances should i go so low?
     
  6. Britprius

    Britprius Senior Member

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    If you discharge the modules slowly once you get below about 5 volts you can take them down to zero at say 100 ma. Then charge slowly at around 2 amps. This can have a beneficial effect as it helps break up large crystals that have formed in the cells bringing them back into use. Discharging the modules quickly down below 5 volts will almost certainly destroy cells with a low state of charge by reverse charging them.
    If you have rehydrated the modules charge with them unsealed. If you charge with them sealed you must have them in compression.

    NiMh cells can withstand over charging, and reverse charging as long as the current is kept low. In the case of over charging all the overcharge energy is given off as heat. It is heat that does the damage in this scenario. Warm is fine, hot is not.

    John
     
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  7. Shaked4040

    Shaked4040 New Member

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    I just tried using pressure to open values - first cell go up to 180PSI, no opening, thats when i stopped.
    second cell 160 PSI, nothing opened, all pressurised air came back from the same hole it came in
    any ideas?
    Battery is still in the pack thou im throwing anymore time on sealed modules and rehydrating them all and seal at the end

    Im charging at 4-5 amps to get them bubbeling and 1amp cycles to balance, can this cause them any heat damage at this current? (No adjucent modules are treated at the same time)

    So below 6 at 0.7A
    Below 5 0.3
    And below 3 (not sure if im gonna get there 0.1?

    After charging to full+ should i discharge a bit before moving on or is it unhealthy in any way to leave them like that?
     
  8. Britprius

    Britprius Senior Member

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    Charging at 4 to 5 amps will do no harm providing you monitor them for temperature. In use they will see up to 80 amps charge for short periods.
    Do not worry about leaving them fully charged for periods of a few weeks it will do no harm.

    John
     
  9. Shaked4040

    Shaked4040 New Member

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    Does heating them up while charging break the same crystals? If same results can be achived without risking batt reversal on low voltage sounds better to me
     
  10. Britprius

    Britprius Senior Member

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    Heating the cells helps dissolve dried out KOH/NOH chemicals back into solution it does not break down large crystalline structures. Taking the cell voltages to zero is not a requirement, but it can be beneficial.

    John.
     
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  11. Shaked4040

    Shaked4040 New Member

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    any ideas about the stuck vents?
    took some of them up to 200-220 PSI, only 1 out of 10 i tried opened, it was not stuck as it opened around 80-100 PSI
     
  12. Britprius

    Britprius Senior Member

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    The only way I know is to take the pressure up, but do this with the module inside a container or a sack. If doing it on an assembled battery cover the top of the battery with sacking. Warming the area around the safety valve with a heat gun or hair dryer before pressuring may help.
    The amount of energy released if one explodes is small, but you do not want to be hit by plastic shrapnel or the caustic solution.

    John
     
  13. MTL_hihy

    MTL_hihy Active Member

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    Nice car John, I don't have a Prius either but definitely keep coming back due to my interest in the subject.........at least you stayed in the Toyota hybrid family! Looking for my second HiHy now (my wife stole the other one back because it's running so well), hoping to find a newer one with higher miles again that would benefit from a battery refresh.

    Totally agree, it's not so much the shrapnel as it is the alkaline solution which sill go everywhere and can possibly burn or blind you if exploded. I would keep it under an polypropylene tarp of some kind when doing this as PP is quite resistant to acids/bases.
     
  14. Britprius

    Britprius Senior Member

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    Good to hear from you again MTL. Although I do not participate as much as I did here on PC I still do drop in to see what is happening, and catching up with old friends.

    I now appear on the UK "Lexus Owners Club" forum, but still under the name of "Britprius". Much of the information on the Prius still relates to the Lexus hybrids in particular the Lexus CT.

    John (Britprius)
     
  15. Shaked4040

    Shaked4040 New Member

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    Amazing progress im happy to report
    All of the batteries except for dead one are passing the 5K mark and about half also passed 6K already

    As i overfilled my batteries with the solution i took some of it out and collexted it into a plastic jar (300-400ml went out after more than 1.5L was initially added)
    In the solution i took out i see like a dark gui blur bit more sinking than floating, will i need it? Just verifing if I understood correctly, the NAOH is the electrolyte and thats the only thing in the solution, i added about 15% solution btw
     
  16. Britprius

    Britprius Senior Member

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    I am happy to hear of your good progress. The "solution" is a mixture of NOAH, and KOH, but that is not critical. I do not understand your qiestion.
    , but anything that came out in the liquid can be discarded.
    Keep me informed of further progress.

    John
     
  17. Gorhamax

    Gorhamax Junior Member

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    I'm interested in rehydrating modules for a long term repair, but am skeptical that the proposed KOH to water solution would evaporate out very quickly, possibly within 6 months? If this happens, it may dilute the original gel electrolyte and cause it to evaporate out, as well. (Pure speculation of course) I'm wondering if anyone has tried to more closely replicate the OEM gel-like mixture to reduce evaporation rate and ensure a long term cure. Possibly using a small amount of PVA or similar?

    Are the rehydrated modules still going? Has any one checked to see if their solution evaporated out? A gel electrolyte would likely be safer and longer lasting.
     
  18. terramir

    terramir Member

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    I h8 to revive an old thread, but posting a new one does not make sense if this thread is so full of information until I have actually started the experiments I have planned.
    But I got some ideas I would like to bounce off the OP and some of the other active participants.

    #1 the holes need to be completely sealed after thinking use the drill shavings plus some shavings off a shorted out donor module to melt the holes closed.
    #2 use just enough of a drill to get the syringe in like a #76 for a 23 ga. needle.
    #3 since the guy got 20k miles out of that prius gen1 with 5ml per cell I'm thinking he re-hydrated the gel.
    #4 if I am correct the holes between cells are on the very top in the middle can someone tell me the distance to the top and the diameter of the hole.?
    #5 I'm think9ing 20%KoH should be sufficient but has anyone experimented with more I know people have used less?
    terramir
     
  19. Britprius

    Britprius Senior Member

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    I found trying to seal the holes by melting in more material a bit hit and miss. The finer the hole you drill the easier it is to seal the hole with steel fine threaded screws.
    Watch or clock screws can be bought in very small sizes and can be self tapped into the holes making an excellent seal particularly if the area round the hole is warmed to soften the plastic before fitting the screws. This also has the advantage of being able to add or remove electrolyte.

    John
     
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  20. David Weber

    David Weber New Member

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    Thanks so much for this article, I am currently testing rehydrating cells from my 2004 Prius that sat for two years. I refilled one and it took the full 60 mL. I’m using a 1.5 mm drill and I have stainless steel screws that are 2 mm. These are Panhead screws with sheet-metal threads, I’m hoping that they will seal effectively without having to tap plastic. Any thoughts on this?