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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    Thanks Brad -

    Roy

    That is a good picture

    Thanks

    Roy

    Yes thanks John for the info.

    Brad - I used a self tapping 1/2 inch # 6 sheet metal zinc plated screw that had a cutting end to tap the holes , one screw did all 238 holes very quickly.
    I then filled the holes with distilled water and then installed 238 stainless steel 1/2 inch # 8 sheet metal screws. The threads per inch is very low on the sheet metal screws and would not provide as good a seal as John's high thread machine screw. I am considering a sealant may be required under the heads of the self tapping sheet metal screws as they are screwed in - it would have to be a sealant that bonds metal to PVC to be effective. Since I am doing 238 screws an easy to apply sealant would be needed, I used a battery operated screw gun on a very low torque setting to drill and tap and install the screws so the work time was only a few hours.

    The location of two of the screws that go near the vent and temperature well is critical as the screw will block the vent between the cells if not placed properly.
     
    #141 royfrontenac, May 25, 2015
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  2. strawbrad

    strawbrad http://minnesotahybridbatteries.com

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    For glue I am going to ty JB Weld Plastic Bonder Syringe. It claims to bond polypropylene. Do not confuse it with JB Weld Plasticweld Syringe, it does not bond polypropylene. You could use a #8 machine screw with a fine thread. On my latest two hole attempt I used a 7/64" drill and then #6 stainless machine screws. They sealed without glue.

    Brad
     
  3. royfrontenac

    royfrontenac Member

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    I will look for plastic Bonder syringe it sounds like it could be injected under each screw head as the screw was entered into the hole making it a quick application for 238 screws.

    Thanks

    Roy
     
  4. a_triant

    a_triant Member

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    About module blown off this reminded me i seen same happened on Russian Lexus forum, finally found that message again, the guy showing his module blown off, looks like that after rebalancing because numbers written there, i think this probably happened because maybe a big differences in capacity between modules maybe he not made the pairs equally, and the result was probably that the module overcharged and blown off?

    i will ask him for details, maybe the detail will give us useful info :)

    e76a7aad.jpg

    update: he answered, he just inverted the modules, from side to middle, without even measuring the capacity!

    But as we can see on the photo the modules are not inverted, we can see a temperature sensor and it at side of battery pack, also we see the blown off module #26 between #40 #34, according to my capacity this will be like 1.6Ah between 5Ah and 2.5Ah :eek:

    Alex.
     
    #145 a_triant, May 26, 2015
    Last edited: Jun 7, 2015
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  5. Delemi

    Delemi Junior Member

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    I'd be tempted to try it in my first gen battery and provide results. I have the Chargers to do it module by module. It's an 03 so the cells are about 14 years. Let me see if I can get my hands on the chemicals needed.
     
  6. Britprius

    Britprius Senior Member

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    Thanks. The more information, and points of reference the better our understanding.

    John
     
  7. strawbrad

    strawbrad http://minnesotahybridbatteries.com

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    I have results from adding just 9ml per module of distilled water. The first module had a capacity of 3043 mAh before and 6280 mAh after re-hydrating. The second module went from 4649 mAh to 6334. For the capacity tests I let the modules sit overnight between charge and discharge, The capacity test was run at 20 amp load to 5.4 volts per module. I used two holes similar to what John did to fill the modules full. After 1 hour soak I inverted the modules to let the excess water drain out. The water took some KOH out with it. It had a soapy fell. The modules retained 9 grams of water.

    This method is too messy. Next I am going to try adding 9 ml with just one hole. I think I have a way to distribute the water evenly. I will be off line for a couple of days before my next test.

    Brad
     
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  8. Britprius

    Britprius Senior Member

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    The results still look good with close to original capacities. Did you check the internal resistances?
    I am intrigued as to how you are going to fill evenly with only one hole. I came up with a couple of ideas on this. One by inverting the module completely, but there was no way I could guarantee all the cells would reach the same level, or even all take fluid.
    The soapy feel to the water is indeed the KOH taking oils out of your skin.

    John.
     
  9. Delemi

    Delemi Junior Member

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    I found I can order KOH in either flake or liquid. Liquid has a bunch of fees because of it being corrosive. Flake is about 11$ US per 2lbs plus shipping. Liquid is 26.55$ per liter plus shipping and fees. Should I have a preference? I won't be able to start this project until after my vacation. Riding the motorcycle from MI to Myrtle Beach, SC for 9 days. I am planning to do the whole pack at once. Take initial readings and resistance of each module and again after they have soaked and been recharged. Would flipping the pack upside down after filling allow the fluids to distribute? I know there is a gap; very minute at the top. Here is one that exploded on a battery I rebuilt last year. Notice the round vents going across the top of the cells.
     

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  10. Britprius

    Britprius Senior Member

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    The flake is the way to go because you can adjust the concentration to suit the application. Your paying extra to transport water. When mixing add the flake to water. Do not add water to the flakes!!!!!!!
    You can work out how much you need from my first post.
    Turning the modules upside down causes air locks so the fluid does not move from cell to cell. With a hole at each end and the module laid on it's side you avoid this, and all the cells fill to the same height providing you keep the drain hole on the center line of the module.

    John
     
    #150 Britprius, May 26, 2015
    Last edited: May 26, 2015
  11. nh7o

    nh7o Off grid since 1980

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    These pictures showing blown modules would appear to make the procedure of checking the relief valve a worthwhile effort.
     
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  12. Britprius

    Britprius Senior Member

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    I think it is quite possible that because the battery internal pressure rises so gently when on charge a sticking relief valve possibly releases at higher pressures than seen using a compressor with the attendant high flow, and pressure rise times.
    I agree this really should be part of any battery refurbish process even just balance charging.
    Some sort of cover over even single module while on charge would also seem prudent if the relief valve has not been test. Something like a canvas bag would stop pieces of sharp plastic flying across the work space.

    John

    Brad perhaps I am missing something here. In your post #147 you say you added 9 ml of water to a module then drained it and then module retained 9 grams of water. Since a gram and a ml are the same for water you drained nothing out. ??

    John.
     
    #152 Britprius, May 27, 2015
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  13. a_triant

    a_triant Member

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    I'm also confused, after re-reading later noticed that he says "I used two holes similar to what John did to fill the modules full." :)

    Alex.
     
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  14. strawbrad

    strawbrad http://minnesotahybridbatteries.com

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    Here is some clarification with pictures of my last test. Two 7/64" holes were drilled in the module top. My syringe has a 1/8" needle which makes a tight fit in the slightly smaller hole. After the holes were drilled the module was charged at a 6.5 amp rate just to heat the module up. Near boiling water was pored into syringe which was inserted in one of holes. The module was completely filled with water. DSC00120.JPG

    The water flows out of the second hole when full.
    DSC00121.JPG

    After letting the module soak for one and one half hours it was inverted to let the fluid drain out. After draining the module was 9 grams heavier than it was before re-hydrating. The fluid that drained out had a soapy feel. Some unknown amount of KOH was removed from the module.


    DSC00124.JPG

    The holes were sealed with #6 machine screws. Bubble soap was used while charging and discharging the re-hydrated modules. No leaks were detected.

    DSC00125.JPG

    I will not try this method again. It can not help performance to remove KOH from the module. It is also a mess. I have now tested three modules for the amount of water the plates can retain. They each retained 9 grams of water. The patent also mentioned adding 9 grams of water. For now I will continue tests of adding 9 ml of distilled water.

    I think I can evenly distribute 9 ml of water with just one hole. The hole would be in the side of the module in to the dead air space above the plates. The module will be 3/4 inverted and perfectly level. I plan to build a jig to level and rotate the module around terminals. John has mention airlocks as a problem with just one hole. One easy solution to airlocks is a second hole. I think that having the module 3/4 inverted and slowly adding water will prevent airlocks. Pictures and more tests to follow.

    I have another theory that there is no need to evenly re-hydrate each cell. On charge and discharge oxygen and hydrogen gas are produced. This gas is freely available to each cell as needed. The gassing and recombining will evenly distribute the water. I have no plans to test this theory.

    Brad

    Roy,
    With the pressure gauge I was trying to determine the normal operating pressure of a non re-hydrated module. This is certainly not something to do to every module. The module pressure tested had nearly zero capacity and suffered from self discharge so it was not an ideal candidate to determine "normal" operating conditions. I can say that at 65 psi it was very swollen. At 80 psi it was scary. My guess and concern is that the modules normally stay below 50 psi and never vent. A module that looses 2/3 of it's air space to re-hydrating will then have the potential to generate 150 psi. Of course the safety vent should open at 80 psi. The point is that overfilling a module could take venting from almost never to almost always.

    Brad
     
    #154 strawbrad, May 27, 2015
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  15. a_triant

    a_triant Member

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    Interesting info Brad
    But 9ml per module (1.5ml per cell), that very small amount and it will just wet the plates, then maybe it will dry again very quickly?

    Alex.
     
    #155 a_triant, May 28, 2015
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  16. strawbrad

    strawbrad http://minnesotahybridbatteries.com

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    Hi Alex,

    Maybe the small amount of water will dry out quickly. We do not know until we try. John determined that there was not liquid sloshing around in the modules when they were new. The electrolyte is a gel. We have one old report from John K that he got two years and 20,000 miles of service from adding 5 ml per cell. His test was ended from the car being totaled in an accident. The battery could have lasted much longer. It takes about 10 years for most modules to lose capacity and electrolyte. Is this because oxygen and hydrogen gas are simply hard to contain for that long a period? Or, has the seal on the module been degraded over time? From reading your earlier posts about reconditioning your battery I think yours is a good candidate for re-hydrating. At this point you do not have much to lose trying.

    Here is a picture of the inside of a Gen I module top. DSC00129.JPG

    The same top with 9 ml of water. The water just fills the recesses of the inter cell passages. DSC00130.JPG
    DSC00131.JPG

    Brad
     
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  17. a_triant

    a_triant Member

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    Yeah i'm almost ready :), now waiting only for mini electric drill and a plug tap 1.6mm tool to cut a thread for 1.6mm screw
    Got about 470grams of KOH purity 90.4%, screws m1.6x5mm, and drill bits 1.2mm

    I planing also to weight all the modules before injection and after, since i have modules from 5Ah to 1Ah would be interesting to see how much will take every module, i can't decide now how much to inject, i think i will go with John's method to inject about 11ml to every cell

    This time i will charge at 3A and like before will input charge up to 9200mAh :) only the discharge will take too long.

    IMG_1224.jpg


    Alex.
     
    #157 a_triant, May 28, 2015
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  18. Britprius

    Britprius Senior Member

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    Brad my honest thoughts on on this is that adding 1.5ml per cell does not take into consideration how wet or dry that cell is. Something you were obviously trying to find with your filling experiment. However I fully support all your input to this thread, and in no way am I trying to discourage your efforts.
    Adding some water to a dried out cell or module must make an improvement to it's operation, but feel the optimum level is probably somewhere between your 1.5ml and my level of 11ml. Apart from reducing the expansion space I see no downside to topping up the cells to the top of the plates with the addition of some KOH. The amount I am suggesting requires something in the order 75% water loss"or about 8ml" before the solution becomes saturated at 20C. At that point dry powder may begin to form on the plastic case "no big deal".
    There is much hypothesis among manufacturers as to where the water goes. With prismatic plastic case modules it is believe much water is lost through osmosis through the plastic walls, some is lost as gasses through the vent, and some is lost as hydrogen absorbed into the negative plates.
    The flow of liquid along the inverted top is fine while air can flow freely,but with only one hole filling evenly will depend on how slowly you can inject the water. Slightly to fast and you will end up with an air lock, and at that point you loose all control of levels.
    Please keep adding to these post your findings good or bad. We are all on a learning curve, but I am sure we can say re-hydration does work on undamaged, but dried out modules. I hate to think of how many such modules have been disposed of.

    John
     
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  19. a_triant

    a_triant Member

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    I thought today about what Brad told that if to inject to much then there will be less space and the valve will open quicker, then if it will open quicker what that will cause? maybe only that the water will dry quicker right? then with time when some water will dry out it will reach by itself the ideal level of water where will be much more space so the valve will not open so quickly :)

    Alex.
     
    #159 a_triant, May 29, 2015
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  20. strawbrad

    strawbrad http://minnesotahybridbatteries.com

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    This is a good summary of John's method. If or when a re-hydrated module vents some KOH will likely escape also.

    The last two Gen I modules each weighed 1112 grams when full of water. The first was 1045 dry and I forgot to weigh the second one dry. The first weighed 1054 g and the second 1049 g after the excess liquid was removed. So 67 ml filled the first module 100 % full. The lightest module I weighed dry earlier was 1012 g. It is interesting that the last victims, I mean test modules, each weighed 1112 g when filled fully. This might be coincidence or it might be a constant that would allow a determination of how dry a module is. This is worth testing on a half dozen or so real junkers.

    Alex, I suggest trying 5 ml per cell on your worst modules. You can always go back and add more latter. Other than the holes drilled in the modules, most of what we are doing is reversible. I can start with a little water and add allot of KOH latter. You can fill a module and drain some out latter. Before you open your bag of KOH, Google KOH first aid. Safety glasses and an immediate supply of clean water are a must!

    Brad
     
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