Re-hydrating the battery modules.

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

 

we miss you john, all the best with the lexus!

 

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?

 

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?

 

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

 

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

 

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.

 

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

 

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.

 

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

 

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?