Re-hydrating the battery modules.

I use a bar clamp and a couple of small boards, along with a rubber mallet.

 

Thank you! I finally used the same techinque. At first I was afraid of damaging the modules. I will finalize the installation today and hope to see results.

 

I started of with P0A7F hybrid battery pack deterioraton trouble code and then rehydrated and charged all the modules. Now I have reassembled the battery pack more times I can count, but it is still not working properly.

Atfter first reassembling I was struggling with some leaks, but they are fixed now.

All the modules have gotten much better individually and have correct electrolyte level, but code P0A80 replace hybrid battery pack keeps coming up. I have reconditioned and done some additional charging to weaker modules(according to the live data).

None of the modules have reversed. All can be charged up to 9 volts with no problems.

My questions are:
1) What can be still done to get the pack working?
2) Can the problem be somewhere else with the same code?
3) How are the modules counted? If live data shows that the weakest module pair is 5th, then were I start counting? Right now I have counted from both sides and then reconditioned both.
4) What is the optimal voltage for module pairs while driving/charging?

 

X2

The discharge portion of testing is key to finding weak modules.......many overlook this critical step.

 

By reconditioning I mean I have rehydrated and cycled all modules individiually and some repeated the cycles on the weaker modules.

I have discharge tested all the modules. Before last assembly I used resitor, voltmeter and charger to charge/discharge all the modules to the same voltage to have the whole pack as even as possible.

If I am logging the results, the weaker modules keep changing and there is none that stand out from the rest.

If there is no trouble code, the car is behaving normally and I would say better than others that I have owned. By that I mean that I can drive longer on pure electric mode.

 

Steve,

In hot climates (like AZ) you should expect that many modules suffer early degradation. In milder climes (like here in CT), It is common that only one or two modules need replacing (due to cell reversal) when HV battery alarms go off. The rest seem to recover to reasonable capacity when rebalanced.

JeffD

 

JeffD,

My point exactly. Even in mild climates, modules still need to be replaced. I do not believe he replaced ANY modules. My "experience" includes data from others in milder climates.

Thanks,

Steve

 

You need to put a decent load (200w+) on each of the modules for 2-3 minutes and check the before and after voltage to find the voltage drop for each. Any outliers need to be replaced because those are the modules with weak cells that are causing your hybrid battery ECM to set off the CEL. All you did was re-hydrate the cells and then balance the voltages but this does not help you find which modules are the weak ones.

 

I am using about 90-100w resistor to check do help the discharge, since my charger goes only up to 1A discharge. Of course this I used only up to 5,4V. From there I discharged at 0.3A to 3V. Later I charged the modules with 3A.

I got capacity increase on all the modules from 2000-3000mah to 8000-9000mah. If the module did not get significally better on the first cycle I did 2-3 more cycles and then it got better. Later I have individually done some cycles on weaker cells(based on logging while driving).

For rehydrating I used 20% KOH micture and added about 60ml to each module.

Basically I did everything as described in the first post in this thread.

Chargers I am using:

If I have gotten very nice capacity increase on all the modules then should I still change some of them? Or is there a metod how to properly balance the whole battery pack without special charger?

 

Imax chargers I have are actually original. Amazon link was just the best example I found quickly.

After taking the pack part again and reassembling it and still without a result I have grown tired of this and will replace the bad modules. Where do you reccommend to buy them? Is it possible to get new modules?

 

ok. I am very sceptical of buying used modules from ebay. Not that the ones from Ali Baba would be more trustworthy...

I logged the accelerations and regeneration with diagnostics to identyfy which module pairs are weaker according to this and the when the pack was off the car I took these pairs appart and applied load to them and measured the voltage drop.

 

Both a load test at reasonably high current and watching the self discharge rate (after a few days) are useful in identifying weak modules. If you can find a salvaged, low mileage, Gen3 battery from a recent wreck, the modules should be useful. I would test and re-balance all 28 modules and use them in my old HV battery shell. Then I would fully re-balance and test all my old modules for resale and be a reliable source on eBay as I did a few years ago when my battery failed (only one bad module) at 195k miles.

JeffD

 

X2

Still seems like balancing and then load testing are the issue in finding which ones are bad in the pack.

 

Thank you for your answers!

I found 8 bad modules. It is Lexus GS 450h battery pack so total number of cells is 40pcs. Since modules are the same as Prius, the methods are same.

I will try to find some good replacements for my bad modules.

 

Great thread. My opinion as a chemical engineer working somewhat in electrochemistry:-
Distilled water or better RO water should be used rather than KOH. The original electrolyte is still in there, only water has been lost due to electrolysis. If you use pure water, you can dissolve precipitates that may have formed.

Silicon is not a good sealant for this as it is often acid cure. It is generally resistant once cured but may not cure effectively. I would use polyeurethane instead. The best option is probably polyethylene weld (case material is PE?), or possibly one of the PE compatible glue sticks.

Note that fine threads are generally also shorter (in height) than coarse threads which means they are particularly susceptible to over tightening. A better option may be very small stainless or PE sealed rivets but future holes would need to be in a different place.

 

You can solvent weld PP/PPE. Mostly with very dangerous chemicals (chlorinated aromatics, think paint stripper). I have links but cannot post them here due to restrictions.

I prefer heat except PVC, Epoxies, PS, or Acrylic. It is very difficult to get good PP/PE (or even acrylic) products as a consumer due to safety and competence issues. Note nylon is very easy to heat join but quite difficult to solvent join.

 

In your expert opinion. Would hot air welding using scrape module cases for filler be a viable method for sealing holes?

Thanks, Brad

 

Hi Brad, I would trim down a 3mm PPE welding rod so that it fit in the hole, and heat weld it so that it formed a mushroom cap.

 

hi guys sorry to bump an old (great) thread, considering trying rehydration and cycling over the next couple weeks on a complete pack in a high mileage 08 gen2 with severely decreased capacity, wondered if there has been any further progression with a few things before I get started..
1) fine thread machine screws vs filling the holes with PPE rods
2) the ongoing debate about straight demineralised water vs KOH h2o mix
3) boiled water vs cold
4) last but not least, do we still think a drain hole is needed or is the fill hole perhaps all that's required now testing has established that 60ml is generally the desired amount.

.. cheers
.. .. Matt