PM from "dl3a83" new member (cell imbalance in C-zero)

[kiev]

PM from @dl3a83

I had some bad cells (still LEV50) in 09/2012 C-zero, which were replaced.
I can't charge the car above 75%, the replacement cells are lagging behind when charging by 0.05mV.
I have Diagbox how can I adjust the balance of the cells there?
Unfortunately I cannot find it in the menu.
I did a maintenance where it discharged and charged the car in stage 1, but stage 2 was just a click, which did not lead to any result.
Thank you.

T.

 

[dl3a83]

Today I drove the car, I got the following faults p1a2f p1a4b, yellow car with exclamation mark.

 

[kiev]

Those codes are being thrown because of the imbalance of some cells in your pack. The 50mV difference likely gets even larger as the car is driven and the energy of the pack drops. The DTC is thrown when the difference is over 200mV:

• When the information that the difference is more than 0.2 V between the lowest battery cell voltage and the highest battery cell voltage is received for more than 5 seconds.

The replacement cells must be very closely matched to the rest of the pack before commissioning, e.g. within 5mV.

The balancing function has a very small range for correction since the current is only 100mA at the most and it is not a continuous current.

You would likely have more success and it would be quicker to open the pack and manually charge/adjust the modules. But it is not a trivial task. The individual cells would need to be charged to the same voltage value, then connected together in parallel to equalize, then reassembled in series modules. It might be possible to do the parallel balance at the module level but would require close monitoring to ensure that individual cells were all matching.

 

[MickeyS70]

PM from @dl3a83

I had some bad cells (still LEV50) in 09/2012 C-zero, which were replaced.
I can't charge the car above 75%, the replacement cells are lagging behind when charging by 0.05mV.
I have Diagbox how can I adjust the balance of the cells there?
Unfortunately I cannot find it in the menu.
I did a maintenance where it discharged and charged the car in stage 1, but stage 2 was just a click, which did not lead to any result.

There is no cell balancing option in Diagbox.

There are various reasons your car only charges to 75% e.g
- cell imbalance, i.e some of your old cells hit 4.1V well before the rest of them thus stopping the charge
- outdated battery calibration

Step 2 of the maintenance (after the click) is to fully charge the battery with the ‘granny charger’, once completed reconnect Diagbox to check new capacity value…

 

[dl3a83]

I filled the cells with the lower value to the value of the cells next to it. Average 3,946V.
I put the car back together and charged it. There were 0.020-0.025V differences between the cells when charging.
I was able to charge to 93%.
Today I drove the car, the V value as I drained the "tank" started to creep up.
At about 50% and after driving 53 km the turtle appeared. 1 of the replaced cells dropped to 2.8V.
So I managed to get a 1,000V difference.
I can see another cell that is close to the fallen cell at rest.
Has anyone done cell balancing with HobDrive?

 

[MickeyS70]

… cells dropping 1V under load cannot be fixed with balancing, they need to be replaced I’m afraid…

 

[dl3a83]

My colleagues and I are putting together a cell immerser and I will be able to test the cells with it.
On another topic, maybe someone can help.
A friend of mine did a battery pack conversion, the car works but after 140km the turtle appears, with the new battery pack the drive would be 240km.
Anyone know the brains of the car? How to tell the car has a battery pack with more range under it?

 

[MickeyS70]

My colleagues and I are putting together a cell immerser and I will be able to test the cells with it.
On another topic, maybe someone can help.
A friend of mine did a battery pack conversion, the car works but after 140km the turtle appears, with the new battery pack the drive would be 240km.
Anyone know the brains of the car? How to tell the car has a battery pack with more range under it?

Not elegant, but a quick fix would be to disconnect/reconnect the 12V battery to reset the BMU. repeat when tortoise re-appears.

Have a look below for a better way:

https://www.forums.aeva.asn.au/viewtopic.php?t=5515&start=825

 

[MickeyS70]

My colleagues and I are putting together a cell immerser and I will be able to test the cells with it.
On another topic, maybe someone can help.
A friend of mine did a battery pack conversion, the car works but after 140km the turtle appears, with the new battery pack the drive would be 240km.
Anyone know the brains of the car? How to tell the car has a battery pack with more range under it?

Not elegant, but a quick fix would be to disconnect/reconnect the 12V battery to reset the BMU. repeat when tortoise re-appears.

Have a look below for a long term solution:
https://www.forums.aeva.asn.au/viewtopic.php?t=5515&start=825

 

[dl3a83]

I seem to have found a faulty CMU card in the package. I found Lev50 cells for sale, seller says they are 80%.
What do you suggest to put 80% cells in the 70% battery pack instead of the bad cells?
I bought a tool to test the cells.
Will it cause any problems?

 

[kiev]

Sounds like a good plan. The weak cells can be replaced with better ones and maybe keep it out of the turtle mode.

The cells need to be very closely balanced externally before installation; the balancing function in the car is too weak and slow to make any significantly large correction. It works to maintain balanced cells within 5 - 10 mV or better

 

[dl3a83]

Over the weekend I took measurements on 4 cells.
Cells 1, 2, 3, are old (50% of the pack).
4 cells from a current car, 70% charged.
Results.
All cells charged to 4,1V, loaded with 15A, discharged to 2,8V:
1: 62,1Wh 16910mAh time 1:07:24
2: 38,7Wh 10754mAh time 0:43:01
3: 47,3Wh 12800mAh time 0:51:12
4: 97,3Wh 25731mAh time 1:43:41
I then lowered the A value to 10A, then 5A and 3A to see how much I could get out of the cells (but that's just for experience).
1: 82Wh 23179mAh
2: 58Wh 16697mAh
3: 55.2Wh 15426mAh
4: 109.2Wh 29515mAh

What do you think about it? I wonder if I am right?

 

[MickeyS70]

Hi there
You need to significantly up the current to simulate driving conditions: at full throttle up to 150A are going trough each cell, even moderate eco driving will still be around 50A (1C).

From experience of others replacing a few bad cells will only bring a short term gain, ideally you would need to replace the complete pack, however decent OEMs are impossible to get, a more promising approach is to change them all out with NMC cells, various projects on the go currently…

 

[dl3a83]

I found a broken car, a 2015 C-zero.
I have a Miev, 2012, but it has a bad battery pack.
I would like some advice.
If I want to save the Miev, can I put the new LEV50N type cells in the car?
I know I am missing 8 cells. I would buy those to replace them.
Will it be ok for the car to have Lev50N instead of Lev50?
Will it be handled by software?
I'm thinking of rebuilding the OBC into the other car as well.

 

[MickeyS70]

I found a broken car, a 2015 C-zero.
I have a Miev, 2012, but it has a bad battery pack.
I would like some advice.
If I want to save the Miev, can I put the new LEV50N type cells in the car?
I know I am missing 8 cells. I would buy those to replace them.
Will it be ok for the car to have Lev50N instead of Lev50?
Will it be handled by software?
I'm thinking of rebuilding the OBC into the other car as well.

Not ideal, but it seems OK to replace a LEV50 pack with LEV50Ns, might be difficult to find additional cells that have the same (or higher) capacity than your C-Zero as the weakest cell determines the pack performance.

Also important ist to make sure the added cells have the same voltage as the rest before you install them..