Re-hydrating the battery modules.

I read it the same way. what im not clear on that is, is it tested against the same NiMH build as panasonics?
also, a passage that just adding distilled water is good enough. and a passage that says adding oxygen is also good. but im unclear on the context if thats doable with us DIYselfers.
This is just one paper tho. and i doubt they did every possible thing. I hope more comes up...

People have been adding KOH and/or Distilled H2O with some success so its still better than the alternative (bad battery).

 

I have tried plastic welding the original pp material from dead modules back in to the holes, it tends to crust over after a while and, I guess "wick" koh back through the repair leaving behind a risk of hv leak, and its messy

I had success hydrating modules and restored capacity to some point however sealing the hole properly any way I tried was a bust for me

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I got the impression the layer of crud had to be physically removed, which would be difficult with the plastic housing surrounding the cell plates. A machine could probably be designed to connect to an opened module (with the lid removed) and with high pressure water and some sort of blast medium, circulate it at high pressure to try and take off the material. But I can't imagine anyone doing this without a very expensive custom setup.

Taking the lid off and putting it back on looks challenging. The factory looks like they melted the plastics together. Guessing an expensive machine did that step. Probably some mold that comes down on top of it and applies heat for the right amount of time. It may be within the realm of possiblities for the DIY person, but very challenging.

I think the only way we could rework these would be to have some chemical based method of stripping off the crud, and use a method similar to this thread where two holes are drilled and liquid injected (maybe larger holes so there could be a flow of the 'solvent' back out of the module).

 

Hi Derek,
I agree, doing all that sounds like a big job that requires lots of investment in time and treasure. might be cheaper to buy a new pack.
In my case, i just wanted to learn what i can do to prolong the life of the batteries at the lowest cost possible and extending the life of the car i like so much. learning what to do and what not to do helps me with that goal.
cheers!

 

How much to fill each cell is important I think. I started off with 9mL but I think the best approach might be to test the cell, however best you can (load, capacity etc) and add in a mL or 2, then retest. I think having too much electrolyte is a serious issue. It was brought up how more fluid inside the cell will displace the air inside and leave less room for the air/gasses to expand. I think its very important not to overfill cells. Without any way to really see inside and tell how dry the cells have become, the only approach I can think of is to in a way titrate, that is keep adding fluid until load testing or capacity starts to see diminishing returns. Also if a cell doesn't respond to more fluid, its probably not dry but formed the crud on the surface of the plates as described in that study posted earlier. After doing this rehydration, I can say with certainty that rehydrating cells only helps some of them. As the prius regeneratively brakes or other high amp events, I'm thinking the cells that are weak take the brunt of that and are being overcharged. The higher capacity better condition cells are able to take the amps, but the weak ones seem to become even weaker quickly. I'd also guess that when some cells are getting worse than others, the bad ones take some of the charging load off the better cells. It would be interesting to test a huge amount of cells and see how many of these weakened cells have just dried out vs forming that crud. Or if its a little of both.

 

Sealing the module, so it never leaks after rehydrating, is the tricky part. Here is a tutorial on doing this process, that is fast and easy.

Perfect module resealing tutorial, for the rehydrating process. | PriusChat

 

Goes without saying to clean around the drilled hole before resealing with the screw. Also cleaning with isopropyl alcohol will also slightly soften the PP, gives the super glue some tooth to grab better.

 

This is brilliant I started investigating and testing why these modules fail a few days ago and found at least 2 cells in each module are bone dry on 15 year old modules with over 150k miles from a gen2
Cut the top off one module and aded only distilled water and it works great
From 4.3a to 6.2a capacity

 

Very encouraging post, so I experimented with the 2010 hybrid battery. The method is to drill 6 holes in each cell, add 10ml tap water, charge 3a, and discharge 6a. The experimental results did not increase the capacity. It may be a battery difference. Previously, it was successful to add water to the Honda Civic 2004 battery. The reason is still being explored. I suspect that the grid of the single cell may be damaged. Is it possible for the single cell to be in the reverse state during high current discharge, whether the temperature has a history of excessively high, whether these factors can cause irreversible damage to the cell, or whether the cell has different materials or structures, resulting in a difference in lifespan. It is testing whether deep low current discharge can reverse the cell.
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One should NOT use "tap water" because the contaminants are unknown and may do more damage than good.
Then, maybe the problem was NOT because of drying out to begin with.

 

Yes, there are impurities in the tap water, which may affect the life span, internal resistance, capacity and self-discharge rate. It is difficult for me to find distilled water here, so I first open a few modules and test it. I think the damage will not happen in a short time.
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Think whatever you want but the damage can be immediate.
Bottled "drinking water" would be better than what comes right out of the tap.......probably.

 

Tap water is full of calcium carbonate, chlorine derivatives (to disinfect it), and most likely iron ions and tiny bits of rust. In a bad scenario possibly even some lead. None of that belongs inside a NiMH battery. A gallon of distilled water at the supermarket is only $1 or so, hardly a prohibitive cost since that should be enough for what, ten, modules?

I would guess that supermarket distilled water doesn't have any of those ions, but it might have some plasticizers in it which have leached out of the jug. Chemistry being what it is, those might not be so great inside a battery either. Probably the battery manufacturers make their distilled water on site (it isn't difficult) and keep it in tightly sealed glass containers until it is used, to prevent contamination, including from CO2 dissolving into it from the air.

The amount of "stuff" in water changes its resistivity, see

Resistivity - Aquaread

I have seen water very close to "pure" in research labs, but I'm not sure where one would obtain water that clean outside of that environment.

 

You really should read the original post a bit more carefully.

 

There used to be a Honda Civic 2004 model. The battery light of that car was on (ima). The inspection found that the battery capacity was too low. Later, I bought the old 2006 Civic car battery, which was not ideal. Later, someone added water to the forum and tried it. As I tried, I added water to the 2006 battery, but the capacity did not increase. After adding water to the 2004 battery, there was a huge improvement before and after water addition. The discharging and charging of the two batteries are slightly different. The 2006 battery seems to have a higher voltage during discharge, but the charging cut-off voltage is not high, and it will generate heat after recharging. It can be understood that the charging and discharging voltage range of the 2006 battery is smaller. The 2004 model can be charged to 9v, which is not very hot, and the voltage during discharging can also keep a steady drop around 7v, unlike the 2006 model, which drops rapidly when it is discharged to 7.2v. So I suspect that there are subtle differences in structure and components between these two batteries. From the point of view of internal resistance, the internal resistance of 2006 is lower than that of 2004. So I think the same situation will happen to Toyota batteries. I think the failure rate of the third-generation battery seems to be very high. I did not succeed in adding water. Is this similar to Honda batteries, or that the quality of the old batteries is better? What do you think? .
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I think you are talking about an ENTIRELY different kind of battery.
12 V batteries with caps are intended to have water added.

 

It is also hybrid, Honda civic Hybrid, its battery is cylindrical, the drill hole needs to be very careful in position and depth, it is easy to damage the internal electrode film.
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That does NOTHING to clarify which battery you are talking about.
Is it the "standard" 12 V accessory battery.........or the high voltage hybrid battery ??

Not that I really care, because you should NOT be adding anything to any battery that was not designed for that.

 

Thank you for your reply. Sorry for not expressing clearly. My writing level is very average. Please forgive me.
What I want to express is about hybrid batteries. The owner of this post and many friends have introduced the method of repairing the hybrid battery. I am a newcomer. I am thinking why there are fewer and fewer people paying attention to this method. Is it because this method has limited effect?
In addition, I bought 15 pcs hybrid batteries today, and I want to test whether there is a repair difference between the second-generation and third-generation batteries.
Attach the code of the newly purchased battery and the obd test result, which is the voltage data of the battery in the car during high current charging and discharging.

 

Yes.
And sometimes more damage is done than good.