Re-hydrating the battery modules.

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

  1. royfrontenac

    royfrontenac Member

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    Good thinking - The steel syringe needle could go too deep and cause a problem.I have edited my post to include your suggestion.
    Alex - did you find any other posts as interesting as this one is? I am going to re-hydrate modules (that are located out of the battery on a bench) with the testing procedure recommended by John later in the week and I will report the results to John. I have enough spare gen 2 batteries to do other tests that may be recommended.

    Roy

    Thanks Brad - excellent post :)

    Roy
     
    #81 royfrontenac, May 11, 2015
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  2. a_triant

    a_triant Member

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    Maybe even easier and faster will be if you cut the needle and make it length 10mm, so it will never touch the plates and you will not have to look at mark all the time :) with that way also you don't have to look how much is water you injecting, you can fill it too much and then take the water back to syringe since your needle will reach only 3.5mm above of plates

    10mm is just example i don't have idea how much is better to cover with water the plates, i think John can you tell better :)

    I'm also going to re-hydrate 40 modules battery pack(from Lexus) i'll start soon as will receive everything that i bought from eBay, in my modules i will use M1.6x5mm steel grade 12.9 screws, i wanted M1.4x5 but did not found them with machine thread and non stainless steel as John said in post #48 that stainless steel that contains nickel may can be react with electrolyte, also got 480 grams of KOH this i think will be enough at least to do half of my pack, after i will get more.

    Alex.
    Thanks.
     
    #82 a_triant, May 11, 2015
    Last edited: May 11, 2015
  3. The Electric Me

    The Electric Me Go Speed Go!

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    Fascinating....but dangerous.

    Having hung around Prius Chat for so many years, I realize that there are a percentage of Prius Owners that are far more involved and focused on the specifics of their Prius as machines than a lot of people are with either their Prius or any vehicle.

    But where do you draw the line?
    From Toyota's perspective the hybrid battery is pretty much presented as being a non-user maintenance item. This doesn't stop some Prius owners from a wide variety of rebuilding, rebalancing, recharging....and now re-hydrating.

    I'm NOT against this. Well not exactly.....

    But I think there is a danger, in presenting some actions, that are very technical, nearly if not fully experimental- in a public forum. This has already in this thread been referred to as a new step in battery maintenance. The way the batteries are built? I think to perceive of this procedure as anything like common approved battery maintenance is a dangerous approach.

    My fear is for the young kid, or person just not really experienced or qualified who may read "portions" of this thread and be enticed to try to do something that if done wrong can create a very dangerous situation.

    I think for the vast majority of Prius Owners, myself included, attempting to re-hydrate the batteries on any level is simply NOT a good idea. There is a reason Toyota as an automaker and builder presents the Hybrid Battery as a non-user maintenance item. Outside of perhaps keeping the Hybrid Battery fan clean...Toyota would like you to simply use your battery....until if fails, then let them handle it.

    I don't mean to upset those interested in this procedure. The attempt, the knowledge, is fascinating. But I do think it should be underlined, that this ISN'T a good idea for 99.9% of the Prius owning public. It's a very dangerous procedure, and I think one that should be avoided.
     
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  4. Britprius

    Britprius Senior Member

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    Sliding a plastic tube over the needle cut to the correct length, and taped to the non pointed end will stop the needle at the same point each time. The ink tube from a ballpoint pen (washed out) is perfect for this.
    Roy be careful in your choice of stainless screws as some stainless is eaten by both KOH and NaOH. This is why I said mix the chemicals in a steel or plastic container. Carbon steel is not attacked by the chemicals, and does not rust when exposed to the chemicals. KOH and NaOH can be used for de-rusting and protecting carbon steel. Also be careful of using plated screws including chrome.

    John
     
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  5. strawbrad

    strawbrad http://minnesotahybridbatteries.com

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    DSC00063.JPG Here is another link, this is for the patent on the re-hydrating process.

    Patent US6936371 - Method for recycling battery pack - Google Patents

    The patent refers to the batteries as "electrolyte starved". It also mentions a weight loss of 9 grams and that amount of electrolyte should be divided among the six cells. That is a very different amount than the 22ml per cell being proposed here. It is also claimed that pulling a vacuum on the module will help pull the electrolyte deep into the cell plates. I do not understand why this would be so. I just weighed 20 Gen I modules. One set of ten have a capacity of 4000 to 5000 mAh. They weighed from 1012 grams to 1048 grams for a total of 10,307 grams. The strongest modules are also the lightest. The second set of ten are real duds with 400 to 500 mAh capacity. They weighed from 1033 to 1055 grams with a total of 10,439. That shows a small negative correlation between weight loss and capacity loss. 22 ml per cell would add 132 grams of weight. 22ml per cell will also use 2/3 of the free air space in the module. That should increase the pressure build up by a factor of three.

    Lots of testing needs to be done. Proceed with caution.

    Brad
     
  6. ChapmanF

    ChapmanF Senior Member

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    Micro or milli?

    If the community NHW11 PID database is to be believed, the values read from the ECU represent milliohms.

    -Chap
     
  7. Britprius

    Britprius Senior Member

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    The pressure in a module is not governed by it's free air space. With less air space the pressure will build more quickly, but will only reach the same maximum pressure at which point the pressure relief valve will open.This does not mean the pressure in the module falls to zero. The valve opens slowly only releasing any pressure over the 80 psi level and then closing.
    Further a module that is full or near full would burst with a lot less energy release than an empty module.
    Over pressurizing can only be caused by two things. A stuck safety relief valve or a blockage to the entrance or exit of the safety valve. The fact that the original specification may or may not have used the so called starved system makes no difference.
    Looking at your pictures I would say there are one or two scenarios why the module burst. One would be a stuck safety release valve causing overload of the clamping system which then failed. After the clamp fails all pressurized cells "even if not over pressure" will burst.
    The second is failure of the clamping on it's own possibly due to incorrect torque on the tension rods or incorrect assembly putting uneven forces on the rods, and end cases. The module side wall pressure or force pushing outward at 80psi in both directions is 1.7 imperial tons making the proper clamping vital.
    The electrolyte in a NiMH cell has no significant chemical reaction when the cell is being charged or discharged it is primarily used as an electrical conductor. This is to say it does not change strength or composition during the charge/discharge cycle, and cannot be used as with lead acid batteries to determine the state of charge.
    As stated near the beginning of these posts it has been found that the safety valves do stick. In the modules I tested they required an over pressure of 50% to get them to open. This would increase the side forces to 2.6 imperial tons. Further this can cause them to burst even in a module that has not been changed in any way as in Roy's case. It would be prudent as suggested by ChapmanF to check the safety valves on any modules about to be re-hydrated discarding those that the valve does not open on.
    A test I would like to carry out is to clamp a module and pressurize it with the relief valve sealed to see at what pressure the module case bursts.
    In Roys case the module top edge burst suggesting even more strongly that the pressure valve did not open. The clamping system remained intact, and the car and module continued to work as normal.

    John
     
    #87 Britprius, May 11, 2015
    Last edited: May 11, 2015
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  8. royfrontenac

    royfrontenac Member

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    Thanks Chap - I should have said my cars readings were usually 18 ot 19 milliohms (not micro). that would make each module around 8.5 to 9 milliohms( .0085 ohms to .0090 ohms ).

    Roy

    Roy from Canada here ---

    Many people on this site have very little electrical knowledge yet the site is filled with public posts about removing the battery and its modules and testing them electrically - an inexperienced person can get killed by using information from these posts. Public information about re-hydrating the cells is no more or less dangerous.

    Your post should be taken to heart by anyone who has doubts as to their ability to safely do this procedure but excluding the posts from being public would (in my opinion) not be a good idea. Working around a car (even changing a tire can be dangerous) and is avoided by most of the general population anyway.

    Roy

    The article did not make much sense to me, it really did not say how to re-hydrate the battery in layman's terms I could understand.

    I suppose the term "electrolyte starved" means a battery that has little to no free fluid in its makeup. Examples would be the AA and AAA alkaline batteries we use everyday to power toys, clocks etc. If one of these is cut open it appears dry or electrolyte starved. The cells that most of us are talking about re-hydrating are truly starved because they are very dry when opened up but the original design was wet ( fluid leaked from the Gen 1 cells and a messy sealing process was completed by Toyota ) so they seem to be a wet battery that is completely sealed.

    That being said --- the fact that all these older batteries are actually still working and probably all of them are dried out (after a few years ) qualifies them as "electrolyte starved" .

    A lead acid wet cell battery will not work for long when dried out, so manufacturers installed water caps to re-hydrate the cells as they were meant to work in a wet solution..I see our attempt to re-hydrate the cells in a safe manner as being a logical move to correct the loss of moisture and thus give a longer life to the cells. From a disposal point of view this would cut down on thousands of batteries g being destroyed.
    If the manufacturers could come up with a way to manufacture them with a cap or valve on each cell to allow re-hydration it could give the battery( the same life as the car).
     
    #88 royfrontenac, May 11, 2015
    Last edited: May 12, 2015
  9. ChapmanF

    ChapmanF Senior Member

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    Ok, I guess I could have looked at p. 52 myself, which does spell them out:
    Kind of overwhelming, how much materials engineering goes into all the stuff I look at and call "plastic".

    Hmm, everything I can find about any of these resins says they're thermoplastic ... which I'm guessing is what you meant, since the reports of successful remelting would be odd if they were thermoset. Do you remember if any reports included the temperature for successful remelting?

    -Chap
     
  10. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Glue a short piece of very thin tube (vacuum tube, or?) over the needle, so that just enough of the needle protrudes. Easier?

    Yup. I keep thinking that: little caps with O-rings. And that's about all I can think, lol. Just happy to read this discussion.

    OTOH: Caps might not be practical, or only marginally practical, or too expensive, or (bad thought): they purposely omit them, engineering obsolescence.
     
    #90 Mendel Leisk, May 12, 2015
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  11. royfrontenac

    royfrontenac Member

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    John I have bad news about the amount of water to fill the cells, I was using measuing spoons and must have not filled the spoons to the top each time thus giving me overstated readings. I purchased a syringe to day that is used that dispenses the water very accurately and I trust the readings.

    The new readings are ( taken as a average over the 6 cells) is

    1) 7.5 ml fills the cell to a point where the fluid just starts to cover the top of the battery.
    2) 3 ml more puts water up to the 9.50 mm level (the top of my cut).

    I am going to go back and change my original post.

    Roy
     
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  12. Britprius

    Britprius Senior Member

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    Roy did you refill with the syringe dry cells or cells that had already been whetted and drained? The reason I ask is because in my original post I used 60 ml of fluid for 6 cells (10 ml per cell) with the modules horizontal before fluid appeared at the drain hole. This was done purely on calculation. I must admit I could not see where I had possibly gone wrong to such a large degree.
    After reading your post saying at least double this quantity was required I tried drawing off fluid above the top of the plates and found non there. So I assumed you were correct with quantities.
    So it is possible my level is just at the top of the plates, and only possibly 1 or 2 ml more fluid is required. It would also account for why the modules have full capacity electrically. Just raising the filling edge 1/4 of an inch on the final fill would take care of this, and after conformation from you I will edit my post accordingly.
    In your pictures there are what appear to be red pads on the top of the cells (possibly catalysts). Can you measure the depth of these pads because I may be trying to remove fluid from the top of these. Through the tiny holes I am using I cannot see.

    John.
     
    #92 Britprius, May 12, 2015
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  13. nh7o

    nh7o Off grid since 1980

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    I would not be concerned about using real 316 stainless screws for sealing purposes. That material is used as the plates in KOH based electrolysers with no problem. It may not be possible to know what grade of stainless screws one finds on the peg board at the hardware store, however.

    In the U.S. KOH in small quantities can be had from suppliers of soap making materials. The smallest bottles can be mailed without problem, even to Hawaii. Larger amounts are more trouble due to the oxidizer hazard.

    Also, it should be possible to check the fill level with just one insulated wire, cut off flush at the end, and a DVM. One DVM lead goes to the wire and the other goes to either terminal of the module. As soon as the end of the wire hits the electrolyte there will be a sudden jump in voltage seen at the meter. A high resistance, say 1 Meg across the leads would make a more definite reading.

    I have been helping a neighbor recharge his genII battery, and swapping cells. There are some rejects to play with, so I will try this out soon. Just the sort of game that retired EE's can play.
     
    #93 nh7o, May 12, 2015
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  14. Britprius

    Britprius Senior Member

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    After drilling one hole and clamping the module pressurize the module to check the safety release valve. On the modules I had they were stuck and did not open till 120 psi (should be 80 psi) I tested the modules to 160 psi but did not go higher for fear of it bursting.
    I used one of those 12 volt mini tyre compressors to do this.
    Please let me know the results.

    John
     
  15. nh7o

    nh7o Off grid since 1980

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    What are you using to clamp the module?
     
  16. royfrontenac

    royfrontenac Member

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    Hi John - I will measure the pads tomorrow and report.

    I had drained all the fluid out of the one cell I used to give my original ml readings - the module then sat open to the air for a few days.
    My second set of ml readings were taken using all 6 cells - all were very close to each other except the fill over the cells was a little different because when I cut the top off the battery it left some cells with a higher wall to fill the water up to the top (crooked cut).Since I emptied the water out immediately after the measurements there was very little time for absorbtion (maybe 10 minutes) . I did not have distilled water to put in the cell so I used tap water so I did not want to leave it in the cell.

    Roy
     
    #96 royfrontenac, May 12, 2015
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  17. strawbrad

    strawbrad http://minnesotahybridbatteries.com

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    View attachment 79505
    John, have you tested the normal maximum operating pressure of a non re-hydrated module? We know that modules rarely vent. So it would follow that the pressure stays below the 80 psi limit of the valve. Let's assume a normal unadulterated module has a maximum pressure of 40 psi. This is just a guess that should be confirmed with testing. Such a module would swell under pressure but not vent. Now take the same module and fill 2/3 of the free air space with electrolyte. The amount of gas that can be produced from overcharge will not change. But the gas now has 1/3 of the space to fill. You are correct that the pressure will now build quicker. But now there is a potential for 120 psi to build. Maybe the vent will work. Maybe the module will break. Maybe the module will hold.

    Much testing to be done. Be careful.

    Brad
     
  18. hybridbatt

    hybridbatt Junior Member

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    It was a Gen 1 John
     
  19. Britprius

    Britprius Senior Member

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    Brad.
    I think in general we are reading to much into the venting of the battery. It is not some catastrophic event rather a gentle release of excess gas. This is of course dependent on the relief valve doing it's job.
    We do not know the modules rarely vent. This is just an assumption, but if this is the case would also prove the amount of gas produced by the modules is very small. The relief valve outlet is only 1.5 mm in diameter, and this is to vent 6 cells assuming they all gas in a module at the same time.
    To put it in perspective it is probably the equivalent of a mouse breathing out in volume terms when the valve opens. As soon as the pressure reaches the valve limit the gasses start leaking out, and as soon as the pressure drops "which will be almost immediately because of the small volume above the plates" the valve closes.
    If we over fill the module to the point it is full there would be a small amount of liquid pushed out of the valve, but no one is suggesting we do this.
    If we overfill so that the gas area above the liquid is half of it's intended volume the same amount of gas will still be produced, but will start venting a little earlier. The module will still dry out over a period as with the module when it was new. However if it now contains more liquid than originally it will take longer to dry out till the point the module begins to fail again.
    If you are concerned about overfilling fill to the level as in my 1st post as this is just level or slightly below the top of the plates.
    I have already tested modules to 160 psi and that is double the release limit. I am not saying this is a safe limit either, but a limit I have taken 2 modules. This is why I have already stated I would like to test a module to destruction to see at what pressure it bursts.
    The smaller the volume of gas under pressure in a pressure vessel (the module) the less the amount of energy released if the vessel bursts. This is why pressure vessels are tested while full of water.
    So if we have a module burst inside the battery cover in use. Toyota must have allowed for this for safety reasons. The cover is designed to withstand that event. If the We have the same module burst, and it is over full the burst will be at a lower energy level so the cover will have no problem containing it.

    John
     
    #99 Britprius, May 13, 2015
    Last edited: May 13, 2015
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  20. hybridbatt

    hybridbatt Junior Member

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    Hi John, here is a bit of usefull info the stuff in this link Thaumaturgy Clear A Drain 1L | Travis Perkins is a mixture of 10-30% KOH and 10-30% NaOH making a maximum of 60% right? So typical me I wanna know what the other 40% is so i rang the manufacturer basically it is water but not distilled or demin, the advantage of it if it could be used is its liquid?? what do you think??
     
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