Re-hydrating the battery modules.

My bad/dry blades came in at around 1030gm, good ones are about 1080gms. What have you seen for blade weight?

 

Does anyone have a photo of the recombiners? The ones in AGM lesd acid batteries don't require pressure but do create heat when actually doing the recombining, I can't see that being a good thing inside each module that already suffers from heat issues ....

T1 Terry

 

GOOD NEWS EVERYONE;oP

Here is the mystery of the valve, a rubber plug/cylinder!

The black object under and behind the cup is a piece of wire to hold the cup up
so I could photo through. Just 3 pieces to the valve assembly.

The plug is snug in the cup.
Bottom of the cup is flat and the plug seals the hole.
Over pressure compresses the plug(in theory) pushing it up.
Gas flows through the eight channels in the cup and exits through the cross/hole in the top.

Perhaps the rubber is losing it's compressibility or drying out over time...

 

Now I just need to find some Gen 4 modules so I can chop one up and compare!

 

mine opened at 90 psi, there was zero visible change in the case at 90 psi, swelling and gassing are independent of each other and not related.

 

Still confused, a drawing might help. This is what I think you said (in semi patent speak):

A battery pressure release valve mechanism comprising:

1. A solid black rubber plug with a cross embossed on one end. (Both ends? Why is that cross there - why not a completely flat end?)
2. A plastic cup. Said cup is a cylinder fully open on top and closed on the bottom, other than a single small hole in the center. The bottom of said partially closed end is flat on both surfaces. Said cup has 8 small half cylinders molded into its inside wall, with the approximate center of each half cylinder flush with the cup inside wall, said half cylinders extending the full height of the internal wall. Said cup is a shape which may be produced in a standard top/bottom injection mold.
3. Said black rubber plug is fitted into the plastic cup such that the plug covers and seals the small hole on the closed end of the cup, and is flush with the open end of said cup, and is retained in said cup solely by pressure from the compressed rubber and friction between the rubber and inside of said cup.
4. A battery case containing a hole in which to mount said cup. (Unknowns: the cut is retained in the hole by glue, pressure, melting???)
5. Said cup is installed in said battery hole such that the nearly closed end of said cup is exposed to the interior of said battery.
6. Said valve is normally closed due to said plug covering the small hole in the partially closed end of said cup. Said valve remains closed when exposed to pressures below a critical limit.
7. Said valve opens when the pressure through said small hole in said cup compresses said plug in the direction away from said small hole, so that said plug's bottom face is displaced upward, creating a channel across the bottom of said cup, through which gas and/or liquid travels to reach and travel through the vertical channels around the outside of said plug which are created by said half cylinders, until said gas and/or liquid exits the valve.
8. Said valve closes after an over pressure event when the battery internal pressure falls below the critical limit, allowing said plug to expand to its original shape and once again close said small hole.

OK, if that is more or less correct...

That suggests why these valves fail shut. After they vent residual dried electrolyte fills the channels and/or glues the bottom of the plug to the bottom of the cup.

Given this information it should be possible to open this valve for service by pulling out just the center plug. This would provide a relatively large hole to put water in. Presumably that is not so easy, it must be in there pretty firmly. I bet though that if a hole was carefully drilled down the center for, let's guess, half its length, and then a threaded bolt twisted in, it might then be possible to pull the plug out using the head of the bolt for leverage. Or maybe a special tool, like an 8 sided pair of tweezers could get in between the rubber and the cup, compressing the rubber in on all sides, releasing the friction grip on the 8 half cylinders, and it would just come out. I'm thinking something like this cork puller, but 8 fold symmetric (picture won't post, this is the URL
https://images-na.ssl-images-amazon.com/images/I/31cePxlveHL.__AC_SX300_SY300_QL70_FMwebp_.jpg


Then a replacement plug (getting that will be the rub) can be tapped into place. That would reseal the battery.

My guess though is that this isn't quite how the valve was made originally. I bet they pressed the rubber plug into the cup before installing that part of the valve into the case. That way they could easily test each valve before installing it. So tapping in the plug far enough to seal, but not so far that it presses too hard, and won't open at the right pressure, might be tricky.

Another possible issue, the force to tap in/pull out the plug might be too much for whatever is holding the cup into the case, and might break it loose. The 8 sided puller idea would still work I think (since it decreases the force needed to remove the plug). Conceivably it could also be used to put a plug in, and then push down on the plug through the hole in the center of the puller while it is carefully withdrawn from the cup.

 

just drill the battery, tap it, plug it with a plastic or nickel plug, mine survived 90 psi no issues.

get a rod of compatible plastic rod, thread the outside, cut it into 1/4 inch wafers, slot the tops, instant plug

 

I have a question, maybe someone has tried it and let us know.

A 25G x 5/8" (0.5 x 16mm) needle is thin enough to enter the vent, and just about long enough to pierce the rubber thats inside the vent to inject the liquid wether its water or KOH or NaOH.

I wonder if this is a quicker way to re-hydrate each module without drilling nor plastic welding.

The hole made by the needle should be small enough so it is immediately "forgotten" or "disappears" once the thin needle has come out of the rubber.
Maybe this tiny hole will no longer be there and does not affect the pressure at which the vent valve opens...

Anybody tried this?

 

Probably work, issue will be getting the fluid to travel through the gas channels connecting the cells.
Might have a vapour lock, rigorous vibrations may do it.
Also try ~3ml/cell first, 10ml/cell made a lot of pressure(bad).
Forced it's way past the M2 nylon screws and JBweld plastic-bond caps covering the heads.

 

this fellow has good content and can use more subscribers.

 

If distilled water is not available, can demineralized water be used? On the bottle it says suitable for batteries.

 

Use demineralized water in batteries? Depends. Distilled water should be completely free of minerals and other contaminants. Demineralized water can be that clean, but as far as I know there is no guarantee that a bottle of store bought "demineralized water" is. Many research labs need water that is super clean, which is determined by measuring its electrical resistance, and they usually achieve this by putting tap water through a series of resin filters (like the one you might find under a sink) with the end result being indistinguishable from distilled water. This is faster and cheaper (energy wise) than distilling it. That type of "demineralized water" would be fine in a battery. Is the bottle of demineralized water at the grocery store that clean? Who knows? The batteries referred to in the label are lead acid batteries, and they are probably less picky about contamination than a NiMH battery.

You could measure the demineralized water's resistivity yourself to see how pure it is. This describes in general terms what you need to do:

https://www.labmanager.com/resistivity-conductivity-measurement-of-purified-water-19691

The main problem is that the resistivity of pure water is very high at around 18 MOhm/cm^2, so with a pair of 1 cm^2 plates 18 MOhm resistance. Typical multimeters cannot measure that, they top out around 2 MOhm (usually written as 2000k). You could make up a test cell though using much larger plates to get the resistance down into a region more easily measured. A pair of plates 3cm x 6cm in size which are separated by a water filled gap of 1 cm would read around 1 MOhm with pure water, which you should be able to measure. The plates themselves and the container they are in must be very clean before the test or even the purest water will read as somewhat contaminated.

Probably easier to just buy some distilled water. Or how much do you need? Make some. Place some of the deionized water in a clean pan, get it boiling, prop up the lid at a slight angle and tilt and collect the condensate in a suitably clean container. Discard the first couple of collections as it will have picked up soap, sweat, and other contaminants from the lid. Note, I don't have anything around my house that I would consider to be "suitably clean" for this application.

 

I have a multimeter topping at 20 MOhm.
I used the tip of 2 thee spoons trying to keep only 1 square cm submerged and at the distance of 1 cm from each other.

Tap water measured 0.20 MOhm.

Demineralized water measured more or less 10 MOhm.

So, that's not so pure...
I distilled some water, but it measured 0.10 MOhm, I think the pan or the bottle were not clean.
Next time will definely buy distilled water.

The thing is I have already rehydrated 2 modules 2 days ago, and currently commuting to work. So far I have measured a slight IR decrease. I haven't measured the capacity yet, but here some pictures before and after rehydration, the block #5 is the one.

the voltage is higher compared to other blocks during charging and discharging.

I didn't have time yet to do a good balancing of the whole battery , that will come this weekend.

 

I found a scale of resistivity / water purity level and added additional screenshots of before and after re-hydration.
10MOhm CM is considered between pure and ultra pure.
IR is decreased 10% compared to adjacent modules at 60% charge.

 

Getting water to the point it is like a chemical reagent (water with no impurities) is a pretty involved process. It probably doesn't need to be that pure to go into a NiMH battery for rehydration, but we don't really know how pure is pure enough, and we certainly don't know which contaminants are a problem in tiny concentrations and which aren't. Store bought distilled water is pretty clean but it isn't reagent grade either. That said, I think the largest concentrations of what contaminants there are in store bought distilled water are likely to be mostly plasticizers which have leaked out of the plastic storage bottle (especially if it was ever left in a hot place), rather than ions of potassium, sodium, or chlorine which have sneaked past the distillation process. My gut feeling is that plasticizers would mostly stay in solution in the electrolyte and not interfere with the chemical reactions going on at the two battery electrodes, but that is just a guess. There is already potassium in the battery (used in the electrolyte as KOH), so if a little potassium snuck past the distillation process it is likely at a much lower concentration than what is already present and won't hurt. Na+ or Cl- ions might be a problem though, as I don't think there is much if any of those in a NiMH cell normally.

 

Where did you find that weight, 1080 grams?
I weighed about 300 modules and the heaviest was 1043 grams from 2008 prius with 97k miles.
Primearth modules are even lighter than Panasonic ones. There is no fresh Panasonic modules available any more.
If your modules weigh around 1030 grams they are dried out and about to go.

 

Primearth and Panasonic modules are the same thing in reality, except that Primearth modules will be newer.

The company started life in December 1996 as Panasonic EV Energy Co., Ltd (and I believe this company was a joint venture between Panasonic and Toyota, but don't quote me on that).

In June 2010 Toyota sold its share in the company to Panasonic and the corporate name was changed to Primearth EV Energy Co., Ltd.

The history of prismatic battery modules began in May 2000 with the development and mass production of prismatic NiMH batteries (resin case) for hybrid vehicles (NP1.0). In July 2003 development and mass production of the improved prismatic NiMH battery (resin case) for hybrid vehicles (NP2.0) began. Finally, in February 2005 development and mass production of the metal case prismatic NiMH battery for hybrid cars (NP2.5) began. These NP2.5 battery modules continue to be manufactured under the Primearth brand.

Lithium Ion prismatic battery module production began in September 2009. Start mass production of prismatic lithium-ion batteries for hybrid vehicles (Li1.0). These were updated in July 2015 and mass production of next-generation prismatic lithium-ion batteries for hybrid vehicles (Li2.0) began.