Re-hydrating the battery modules.

thanks heaps John, will get to work over the next coupe weeks and post results once done.

Matt

 

The Gen I case tops are much thicker than the Gen II . I have not had good luck with screws on Gen II modules. Even fine and small screws get just a couple of threads in a Gen II module. Use bubble soap to test for leaks.

Please do good before and after capacity testing and share your results.

Brad

 

Hi Brad thanks for the heads up, have you found a reliable way to seal the gen2 modules?

before & afters, yup will do ..

 

The next thing I would try would be plastic welding.

Brad

 

Ok I could plastic weld using scrap from dead modules as suggested earlier, then either silicone / polyurethane or maybe epoxy resin a small plastic patch neatly over the top of the weld just for good measure, if the patch was say 8x8x2mm it should help the weld under pressure.

Interesting now I cant decide! not sure which way to go, I will try each method then decide for myself which I like the most, I don't think accessing the holes a second time would ever be needed, then again

thanks guys will keep you posted

Matt

 

Hi Matt
Roy from canada here to try to help.

I rehydrated 38 modules for a replacement battery for a 2001 prius.

I drilled holes in every module, and added water.

I sealed the holes with stainless steel self taping screws and covered the screw heads with liquid electrical tape.

Some of my sealed holes leaked as the pressure and heat built up in the modules causing the car to give a code indicating an electrical leak from the modules to ground. A proper sealing process must be found as my method is not very good - you will be pulling the battery in and out of the car many times because of the leaks. I have been running the hydrated battery for a few months now and it works well now the leaks have stopped. I had to recoat the modules all over again with the liquid electrical tape and the leaks finally stopped. The problem is the top of the module where you drill the holes is very thin (on gen 2 modules) - I suspect no matter what screw you use to seal the hole will leak under the heat and pressure that exists in the modules when under heavy current loads and the liguid electrical tape is a poor seal.
In conclusion I do not think I will attempt another rehydration project.

A little history.

Toyota had leak problems with leaks at the electrical terminal seals of the 2001-03 batteries. They had a recall that coated all the terminals with a thick gummy glue and even then some of them still leaked. If you ever take apart one of these old batteries you will see the gunk they put on the terminals andthe little pads they installed below the terminals to stop the leaks from dripping down to the metal box.

The Gen 2 terminals have a better seal and do not leak.

 

Hi Roy, thanks for your advise re leaking screws, self tappers are reasonably course threaded yet the screws John uses are fine thread machine screws so im just not sure about using screws! another thing to consider I believe gen1 cars don't demand quite as much from the modules as gen2 (and gen2 not as demanding as gen3, so on...) this means the problem will be amplified in gen2 cars..

I will attempt to plastic weld the holes plus glue patches over the top of the repairs for good measure, wont have a chance to get started for a couple weeks but once I do I will post results!

Anyone have thoughts on best glue to adhere to modules? not so much seal as I think plastic weld will seal but best method to adhere patches, im thinking epoxy resin

thanks again.

Matt

 

Thanks John I will test pop each valve, plastic weld + epoxy a patch over the top to help support the pressure. Will keep you updated
cheers ..Matt

 

Also if you guys are sealing holes with machine screws you want the smallest holes possible to seal well (ideally you have 1.5 x diameter of engaged threads or more to hold). So if the material is thin that means the hole needs to be very small. Also you want the finest threads you can find for the screws because the more threads engaged the better (don't use self tapping screws, no good for sealing.....think small electronics screws) . The plastic material is relatively soft so as long as the holes were close no tapping would be required.

Plastic welding is a good idea but also very dangerous as some areas may become weaker near the edge of the weld so I would be very careful doing this on all your modules before you've perfected the process. I don't know how well epoxy resin will attach to the plastic (HDPE? PP?) so again test before doing them all like this. My preference would still be to use a syringe and very fine/small screws because you then have the opportunity to add more later if need be.

 

John:
I am new to this particular thread but learning and adapting rapidly. Great work that you and others have done. I am working with 6 bad modules. 3 I got from Todd Thompson at TampaHybrids, and 3 I removed from my granddaughter's GenII Prius Battery with 177.5K last week. (which I am now balancing in my garage after replacing 3 bad modules), using a Hitec x 4 charger).
One of the bad modules was a Gen1 , and I cut it open to see the internal structure. BTW, all 3 modules I removed from the 177.5K battery had yellow/white deposits at the terminals, which leads me to believe that the electrolyte was forced out there, and that in turn probably due to a stuck pressure vent valve.
As an experiment, I drilled 1.5 mm holes and filled one of the modules with 70 ml of distilled water. No sign of fluid coming out of the lower hole. I will condition that module per your discharge/charge recommendations. However I am puzzled about how you got the ball inflator into a hole drilled for a 1.5 mm screw. (to check/blow the safety valve). Seems to be not even close !!
I have also constructed a Sodium Hydroxide "distillery" from web based information that I will use to make NaHO and then use that to create a (20% solution) to experiment with the additional 4 bad modules. I will report the results as they become available......RH

 

You can also just use an air gun like this, set your regulator pressure and hold it over the hole to test the valve.



Totally agree with John, be very careful because if one lets go you could be badly burned, I would drape a crappy towel on top of it all just for extra protection in case you do get anything released during the test.

 

Feedback: The one bad module I hydrated with 70 ml of just distilled water was put through John's suggested cycle, although the HiTec chargers cannot discharge at more than about 1 amp. The last cycle was disch to 6V, charge @ 5A to full. Results were not good: The last discharge/charge cycle was 2066 MAhr/4714MAhr, lower numbers than cycle #2

Although as John points out, modules in this configuration do not have to be clamped because of the open "fill" holes, the fill holes blew plenty of electrolyte out both holes during the charge cycle. Maybe I overfilled it. I was caught somewhat by surprise, and the spray bubbles (over 5 hours) hit the bottom of the battery casing and seemed to have etched it. If you do this, I recommend placing the module in a tray, and folding several layers of paper towel loosely over the top of the module, then clean the resulting mess after the process is complete.

I will try the suggested alternatives to pressurizing the module to unseat the check valve tomorrow. Thank you both....RH

 

I would have added a saturated KOH solution not just straight distilled water because you may have diluted the electrolyte and that was why the tests showed worse than before. I would try again with a different mixture and make sure you are able to keep the pressure inside the module since it will expand (gas created) significantly if not contained.

 

Yes, but remember that this is part of a several (6) module experiment. One got filled with just distilled water. I just filled another one with a 20% solution of NaOH, and it has just started it's discharge/charge cycle this afternoon. At least I hope it was a 20% solution, I cannot get any litmus test strips locally to test up to a Ph of 14.. Enclosing a pic of my NaOH "still" happily bubbling away . I am still struggling with testing the pressure relief valves but I'm sure I'll get to that eventually...RH

 

Being a new member, and stuck in the house for a week or so due to foot surgery, I want to thank everyone who contributed to this thread. It's made an awesome 2 hours of reading, reviewing and learning. I have (2) 2005 Prii, both with over 260k miles. Both have had failed batteries, one at the 235k mark and the other at the 255k mark. The first one was temporarily repaired by replacing one bad module, while searching for a good deal on a newer wrecked car. I found a good deal on (2) 2013 Prius C batteries (20 modules each) and used them to build a complete battery with a 2008 housing I acquired. The repaired battery had about 10k miles on it when I installed the replacement that had the 2008 hardware and 2013 modules. That now has over 20k miles on it. About 8 months later I bought the second 2005 that had 255k on it with a failed battery. I took the original battery from the first car straight off the garage floor and installed it. It's still going strong 10k miles later. I bought a complete 2012 battery to have in standby to rebuild it when I have an opportunity. I have 31 years exp in electricity, electronics and mechanics. I have a firm grasp on electrical and mechanical safety, so do not fear for me.

Enough about me. This thread interests me because after I swap in the 2012 modules, I may try this rehydration experiment with the 2005 modules if they test out less than 4000.

I have a couple questions.
(#1) I saw some discussions about rehydrating cells that have 5000+ mah capacity. Why? Aren't these considered totally acceptable capacities?
(#2) I have (3) Hitec X4 AC plus chargers that I've been using for another project. I also have a 2015 battery pack from a 14k mile wrecked prius. I plan to use the 2015 modules to get baseline info for what numbers to expect charge/discharge for a fresh OEM module. I figure I can use this info to compare with older cell cycling info. I saw some discussion about using a 9000mah charge limit. Is this common accepted practice?
(#3) I also saw to expect about 70% charge efficiency ( which would be ~9300mah for a perfect 6500 discharge). Does this efficiency vary greatly with charge rate? I plan to limit all my charging to 1 amp and discharge to 0.7 amp. I've found that the Hitecs start acting weird when using all 4 channels together at higher rates, especially channel 2.

I've cycled 2 groups of 38 modules from Gen 1 factory replacement packs that have modules with 2011 manufacturing dates. I used 8k for charge limit and they seemed to max out between 5300-6000 mah on the discharge, with the great majority around 5600-5700 ( 4 cycles, but the last 3 are typically pretty close) which falls dead on that 70% number. (5650/8000=70.6%) I had started cycling using 7000 limit and bumped it up 200 at a time until 8000. I was reluctant to go higher, but if 9000 or 9300 is the number, i'd give it a try.

 

Hi all, just wanted to post my results from hydrating just one module, so far my efforts have been a flop I think my modules are deplete rather than dry!

*test module original capacity 3800ma @ 20A to 6.4v (before hydration)
* added around 30ml (water only) cycled 5 times charged to peak then discharged at 20A rate to 6.4v after 5 cycles the module still hovering around 3800, no cigar.

May try a couple more modules that are 4000mA+ @ 20A if I ever get time, not a priority! but will post results when/if it ever happens.

Thanks to everyone for the info, will keep an eye on the thread ..good luck with it.

Matt

 

A bit of an update on the 2015 Prius, 14,000 mile modules. All the modules have an October 4, 2014 date code. I just finally got around to checking these modules and thought the readings may be of use to anyone who is cycling their modules. My main goal for this was to see what a typical result would be for a new module, for comparison purposes when cycling older modules using the same exact setup. I do quite a bit of refurbishing of motors and niche automotive items. I plan to provide good used modules on ebay. I plan to provide all information with each module to help ensure buyers know exactly what they are purchasing. If you guys have any input, feel free to provide it. Constructive feedback is appreciated, other feedback is not.....I don't need anyone selling mega-dollar equipment to tell me how f'ed up I am because I'm doing this without his equipment.

I used three Hitec AC4+ chargers. NiMH mode. The charge rate was set for 1.5 amps, no time limit, 9900 max mah and default values for delta V to end the charge. Discharge settings were for 1.0 amp to 5.8v (at the Hitec) which provides 6.0v at the module terminals. Actual discharge rate varied based on real time voltage of the module and was typically 0.6 to 0.8 amps). 2 cycles were performed. (discharge, charge, discharge, charge). I also have a TENMA model 72-7680 programmable electronic load that can handle up to a 60amp discharge for final testing, if desired.

All 28 modules remained in the OEM clamp assembly exactly as it was removed from the hybrid battery pack.
The modules were cycled in groups of 12, 12 and then 4

The module that had been closest to the computer was designated as #1 and the furthest was #28.
Although charge rate was relatively low, I wanted to ensure heat wouldn't be a problem. I built a 1" tall wood frame that matched the outer measurements of the clamped modules, with a funnel at the end (at #28 module) where I mounted a BOXER fan model WS2107FL to force air under the pack, into the 1" air space, where it was forced up between all the modules. I also had a small floor fan to provide extra ventilation to the area where the 3 chargers were mounted (on the pegboard backing of the workbench). This worked great, as no temperature increase was noted on any cell during the entire cycle procedure. (using a Fluke model 62MAX+ temperature gun)

The first group of 12 was 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22 and 24
The second group of 12 was 27, 25, 23, 21, 19, 17, 15, 13, 11, 9, 7 and 5
The last group of 4 was 1, 3, 26 and 28
This ensured no 2 adjacent modules were charged at the same time.

The initial discharge values varied between 4015 and 4826 (battery has been sitting in shop since august)
The first charge stopped at 9900mah for every module except #3, which stopped at 9545mah.
The second discharge varied from 6673 to 6942mah. Higher than the 6500 rating, but not totally unexpected with the low discharge rate. 6 modules were in the 67xx range, 18 in the 68xx range, 4 in the 69xx range.
The second charge cycle went to 9900 mah on every cell. Even at this level, there was no heat generation and no swelling.