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HCH 2009 IMA reconditioning in progress

23K views 172 replies 13 participants last post by  HonkingAntelope 
#1 · (Edited)
Hello everyone,

I am reconditioning my IMA battery pack. Or at least that is what I hope I am doing.

For those who are interested, I am sharing my google drive folder with the following information:

- Pictures from my IMA pack dismantling and setup for reconditioning.
- A document with a RAW collection of information from my research. There you will find all relevant information IMO about the subject. Many pieces of posts from this forum as well.
- A report of my progress which is a living document for now.
- An excel where I collect my data of my cells and modules (pairs of sticks)

Link: https://drive.google.com/drive/folders/0B4RNujDTR9UCYlJZVlRIMm16UG8?usp=sharing
 
#154 ·
@Paddow thank you for these posts. I have built an Arduino-based stick conditioner that pierces the wrapper so that I can selectively discharge individual cells. I just saw this thread for the first time, and your posts confirm things I'm seeing in my early tests of charging and discharging.

Thank you so much for communicating what you have learned. It is helping me refine my own pack rebuilding process. Your new car sounds great, and I wish we had a forum for it here, so that we could hear about what interesting project you might wrap around it.

Best!
 
#156 ·
Update. My friend who got my HCH2 got an IMA light. It has been 9 months since the last reconditioning.
I am sure that the problem was that they went on summer holiday for 5 weeks. The car stood still for 5 weeks.
So, tomorrow she's bringing it to me. I will do another reconditioning for them. Hopefully it will be good until their next summer holidays. LOL.
Setting up the battle station!
 
#157 · (Edited)
New reconditioning. I pulled the pack, took it apart and measured the RV of the subpacks. And then I measured again after 24h.
The RV variation after 24h is 0,18V from max to min. The self discharge of the subpacks is between 0,2 and 0,25V after 24h. So, not so bad. I see no outliers so I will not go to the cell level this time.
My plan is: Charge per subpack at 1A to full. Discharge to 1V/cell, so 12V per subpack at 1A. I choose to do the first cycle at low current to be gentle. Then I will do 2 more cycles at 3A. I will record the capacity of every charge and discharge.
I will not do a deep discharge this time.
Maybe next year, I might do a deep discharge, but for now the subpacks look quite good.
Deep discharge I only do at the cell level. If I do a deep discharge on a whole subpack, the cells do not discharge at the same rate when you go under 1V/cell. Some will inevitably reverse and some will never go under 0,7 or 0,8V.

By the way, when I was disassembling the pack, one screw on one of the sticks was loose. That is a bit worrisome. I hope this will not happen again....
 
#158 · (Edited)
Reconditioning is done and the IMA works as it should. Still... the cell level work with a deep discharge gives better results.
During the test drive I did, the car did 1 positive recalibration, which is not strange. But every time I did proper cell level reconditioning in the past it never recalibrated after installation.
 
#159 ·
Happy New Year Everyone!

The last reconditioning I did was about 3 months ago.
My friend brought the car back with the IMA light back on. And she tells me... you know.. it came on about 2 weeks after the reconditioning! But she did not call me earlier.
Oooops. 2 weeks..
We all know what that means. Right? Yes we do.
There is a dead cell or two in there.
In the coming days I pull the pack to check it. I still have some spare cells for replacements. I hope I can find 1 or 2 good ones.
That's gonna be fun.. NOT.
 
#163 · (Edited)
I need to gather my thoughts and make a good plan here.
First I will start with the modules containing sick cells. And parallel I will recondition the spare cells I have for potential replacements. At the end I can compare them and find matches.
I will do a deep discharge on the cell level and then cycles per module. Then I will let them rest for 3 days and check self discharge, while I go on reconditioning the healthy modules.
If necessary I can do a 2nd deep discharge of only the sick cells and extra cycles. Let's see. This is going to take some time.

For the first discharge step to 1V I group healthy cells.
Sick cells I do individually.
The deep discharge will be on the cell level.
Then I will do 1 cycle per module.
Then 3 cycles for every sick cell individually.
Then 1 more cycle the whole module.
3 days rest and check self discharge of cells.
 
#166 ·
Rectangle Font Parallel Pattern Number


This is the capacity discharged below the 1V level.
In combination with the previous table we see that most of the sick cells were still holding quite some amount of charge. Plus now after this step all the cells are perfectly balanced.
So, I would say that the number of suspects is now down to 4. Perhaps 3. I have done now extra cycles the 4 suspects individually and an extra deep discharge down to 0,1V.
I am curious about cell 9.10. It was completely empty. The cell that worries me the most is 7.10. It was holding very little charge and had an RV of 1,2V. That one is the most suspicious.
I am now cycling the other subpacks. In a couple of days I will have results about the self discharge of the suspects.
 
#167 · (Edited)
Font Pattern Number Parallel Screenshot

It is now 2 days after the final charge following the reconditioning. This is the RV of the cells. Cell 10 in all 3 subpacks show a slightly higher self discharge.
I would say that it is not dramatic. There is no dead cell, or the difference would be higher.
I think I can cycle those cells 1 more time and it should be ok. I am very happy that most likely I will not have to replace any cell.
 
#168 ·
The reconditioning is done. As good as can be.
Honestly I have no idea how long those suspect cells will last. We will see. If my friend gets an IMA light in the short term, at least I know which cells need to be replaced.

Note to self:
Prime suspects: 1.10, 7.10, 9.10
Secondary suspects: 1.1, 7.5
 
#169 ·
The pack is back. 7 months later.
The same suspects from last time are the problem cells now too. Not good.
I doubt reconditioning will fix them.. but I will try.
This pack has had a good and long life. Replacing those bad cells is very hard and it might give it another year before some other cells start to give.
Perhaps it's time too look for completely new subpacks (when it throws the next IMA light.)
 
#170 · (Edited)
I have been wondering if dendrites are the cause and if they only break during discharge, thus only requiring a small amount of new growth to restore them. I wonder if a carefully thought out high energy discharge could be crafted to prefer the low impedance path and make it harder for the dendrite to reform without causing collateral damage.

Of course, replacing the problem stick with one that was charged and left sitting for four months to surface a hidden high self-discharge cell would be better?
 
#171 ·
To my knowledge, chemical deposits (perhaps dendrites) and/or corrosion kind of damage inside the cell (mainly on the poles) can be reversed by deep discharge and cycling.
Permanent damage happens when the separator inside the cell is damaged. That is some kind of polymer membrane..? Not sure. This kind of damage can not be fixed.

I am not talking about replacing a stick. I am talking about replacing individual cells with used cells that I know are good.

I will do a more meticulous reconditioning on those cells now and if by Christmas the pack comes back with again the same sick cells... then I know they can not be saved.
 
#173 ·
I guess when those packs were being designed, there was a good bit of magical thinking going on that the technology was going to get better and bring the costs down low enough that swapping a worn out pack with a new one wasn't going to cost any more than doing the timing belt and water pump would on engines with one did.

That didn't exactly happen. Still beats the newer EV designs with the battery being a structural part of the body and weighing half a ton or more
 
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