Not charging - 1 cell shows 96V instead of 3,75V

[elsteff1385]

Hello all,

Thank you for this forum with all its information. It is very helpfull so far.

Can you please share your thoughts about whether i am on the right track to fix a 2012 Citroen Z-Zero 16kW (identical to i-MiEV)?. VIN VF71NZKZZBU903312

The car starts and goes into Ready. I can drive it forward and backward.

The car won't charge. Upon pluging in the charger, the fan starts, the charge LED lights up, but few seconds later charging stops.

I have checked and found out that CMU 09 cell D reads 96,83V instead of 3,75V.
If i think about this, it makes sense that the charging is intentionally precautiously stopped, because of the high voltage reading.

Would swapping out LTC6802-G2 on the related specific CMU be an easy fix? Or am i missing something. Any thoughts are much appreciated.

Thank you sincerely!

Leon (Netherlands)

 

[kiev]

Can you read out any DTCs with the scan tool?

Normally i would say that your OBC has blown something on the AC Input section to exhibit symptoms such as you describe. But the CMU voltage is a new wrinkle to the puzzle.

i would guess that one of the resistors in the voltage divider network on the CMU board is out of spec giving the false voltage reading.
Or as one member found,

Anyway it turned out to be a single blown smd fuse between cells with faulty reading.

To access the CMU boards requires dropping the battery pack and opening the lid, pulling the module, etc.

If you are electronic and software expert then you could install a CAN bridge on the BMU to intercept the CMU signal and correct the reading before the BMU sees it. But that is a lot of work of a different nature than nuts and bolts of the pack disassembly.

CMU Board thread:
https://myimiev.com/threads/cmu-board-notes-eprom-cell-re-numbering-can-messages.4302/post-39002

CMU-BMU CAN Buss details found in this thread:
https://myimiev.com/threads/main-traction-battery-upgrade-i-miev.5458/post-47689

 

[MickeyS70]

I have replaced the LTC chip myself as no phone shop would touch it, might have better luck with a laptop repair store. Anyway I got a hot air solder station and managed just fine.

But Kiev is right it may be just a blown SMD fuse.

Tip: do a bit of practice with some obsolete smd boards first to get a feel for the process

 

[elsteff1385]

hi Kiev and MickeyS70. Thank you for your replies.

I will check with the iCarsoft interface again to see if there are any DTCs stored and in what module. Will get back to you asap.

To be sure: can you point out to me where i can find the voltage divider network on a CMU board? I don't know where to locate them.

I do know where to find and how to check the SMD fuses. I will make sure to test them.

I indeed am unable to go via the CAN/BMU intercept route. I need to go for the nuts and bolts fix

 

[MickeyS70]

hi Kiev and MickeyS70. Thank you for your replies.

I will check with the iCarsoft interface again to see if there are any DTCs stored and in what module. Will get back to you asap.

To be sure: can you point out to me where i can find the voltage divider network on a CMU board? I don't know where to locate them.

I do know where to find and how to check the SMD fuses. I will make sure to test them.

I indeed am unable to go via the CAN/BMU intercept route. I need to go for the nuts and bolts fix

Check out below for some pointers

https://myimiev.com/threads/cmu-board-notes-eprom-cell-re-numbering-can-messages.4302/

 

[kiev]

Zoom in on this to see the path for Cell D voltage on your CMU 9 board. The resistors are marked with value; the items labelled A-H are diodes (probably zener diodes).

This picture is from a 4-cell module, CMU 6 or 12, but i drew the green lines for how an 8-cell module is connected.

The balancing resistors are 82 Ohms in parallel, and there is a 100 Ohm between the fuse and pin 16 on the LTC chip. Unfortunately there are no reference designators on the board to help identify components.

 

[elsteff1385]

Bit of a twist...

On my diagnosis device, i used the Citroen C-Zero option to diagnose the car. For cross reference, i thought i'd also use the Mitsubishi i-MiEV option. I did not think of that before.

Turns out the 96V Cell 9D issue does not pup up via the i-MiEV diagnosis! So that is an error in the Citroen area of my diagnosis device, i figure...

In the i-MiEV diagnosis, the BMU does not throw any DTCs.

The EVM does though. It stores P1A12 (common issue), P1AF4 and P0562.

I have charged the 12V battery overnight. Will see what DTCs remain.

I will also first study the P1A12 issue to get up to speed with the info that already is available on the forum.

 

[kiev]

Please share with us which scan tool device you are using.

 

[elsteff1385]

Please share with us which scan tool device you are using.

An iCarsoft CR Pro : https://www.icarsoft.com/Product/s-370-iCarsoft_CR_pro.html
Using latest databases and updates

 

[elsteff1385]

Based on the above new info regarding code P1A12, i went on and unmounted the OBC to have a look inside.

Background info: before i started diagnosing the car, the car has been to a service center for repair. They mentioned they have unmounted the OBC and have sent it to a specialised electronics repair center. The images attached are what i just encountered when opening up the OBC. I have not done any attempts for repair yet.

What i find disturbing:
- little bits and pieces of solder laying around on the PCB.
- solderpads of pin 15 and 16 are clearly missing. Maybe not connecting correctly at the moment.
- "something" is going on at pin 25 and 26. in between the PCB and the waffle there seems to be some additional wiring. I do not trust that at all...
- pin 24 seems to have been bridged. Don't know why.
- both caps have been replaced by 102 versions. the relay is replaced, and one resistor has been replaced. insulation removal porely done, not refitted at all.
- no thermal paste has been renewed. the waffle is bone dry.
- no liquid gasket has been applied when the OBC was closed and nutted back together again.

I'm kinda puzzled on what to do next. My best guess is to start desoldering the waffle to see what's underneeth it.

What a mess!

 

[elsteff1385]

2 additional pictures

 

[MickeyS70]

I'm kinda puzzled on what to do next. My best guess is to start desoldering the waffle to see what's underneeth it.

What a mess!

I would bring the car back to the service Center and get them to clean up this mess..

 

[elsteff1385]

I would bring the car back to the service Center and get them to clean up this mess..

I know... Let's just say that ship has sailed. The car has been with a Citroen dealer from 1st of Nov 23 to 30th of Nov 23. They do not know anything about electronics. Too high tech, according to them...

We picked the car up at the Citroen dealer and took it to the service center, where we bought the car as an occasion. The service center is a Bosch Car Service. The car has been there for the past 3 months. In this time, they unmounted the OBC and sent it to the specialized electronics repair center.

After they got the OBC back from the electronics repair center, they installed it again.

I suspect the car has either never been fixed, since the OBC came back from the repair center, OR the car has only for a short time been fixed/charging, but the waffle has gotten too hot and has caused further damage, since there was no thermal paste reapplied.

We've had insurance company look over this. We've spent €1700 on repairs (which was downgraded from €2300 to €1700 because of the insurance company).

We picked the car up last week, and i (electronics engineer), a friend of the owner's family, have started my research. I hope to be able to fix something.

 

[kiev]

Based upon DTCs changing and moving about, i would have recommended to check the age and condition of the 12V battery to ensure that it is good and strong, since an old, weak or worn out battery can cause a multitude of DTCs.

But someone has been messing with the OBC. It doesn't look like the relay or ceramic resistor has been changed to me.

 

[MickeyS70]

I know... Let's just say that ship has sailed. The car has been with a Citroen dealer from 1st of Nov 23 to 30th of Nov 23. They do not know anything about electronics. Too high tech, according to them...

We picked the car up at the Citroen dealer and took it to the service center, where we bought the car as an occasion. The service center is a Bosch Car Service. The car has been there for the past 3 months. In this time, they unmounted the OBC and sent it to the specialized electronics repair center.

After they got the OBC back from the electronics repair center, they installed it again.

I suspect the car has either never been fixed, since the OBC came back from the repair center, OR the car has only for a short time been fixed/charging, but the waffle has gotten too hot and has caused further damage, since there was no thermal paste reapplied.

We've had insurance company look over this. We've spent €1700 on repairs (which was downgraded from €2300 to €1700 because of the insurance company).

We picked the car up last week, and i (electronics engineer), a friend of the owner's family, have started my research. I hope to be able to fix something.

Sorry I’m confused, the owner paid €1700 for a repair that clearly wasn’t done correctly and instead of bringing it back to Bosch has tasked you to fix it? Maybe talk to the insurance company again, they seem to have more leverage than an ordinary customer?

I would keep quiet about what you found when opening the OBC, otherwise you may be blamed for causing the damage.

 

[elsteff1385]

Sorry I’m confused, the owner paid €1700 for a repair that clearly wasn’t done correctly and instead of bringing it back to Bosch has tasked you to fix it? Maybe talk to the insurance company again, they seem to have more leverage than an ordinary customer?

I would keep quiet about what you found when opening the OBC, otherwise you may be blamed for causing the damage.

Correct. Because of the insurance company in between, the customer settled for a bill of €1700,- instead of €2300.

But: that was communication between customer and the Bosch service directly.

What i find out now, is that the PCB is badly repaired, by another company. So that is a business to business relationship, that the customer himself has nothing to do with.

I am on speaking terms with the Bosch service. They will inform me what specialised electronics company they hired to do the fix on the PCB. I will contact the specialised electronics company and then ask further to see what i can find out. I hope to talk to the repairguy himself. Maybe there is a story behind the PCB that i do not know of, though my opinion is that i should have already (or the owner should have already) know by now from the Bosch service.

I have made tons of pictures of what i found when i opened the OBC. If we have more need for the insurance company, i hope those pictures will be enough. If not, at least i tried.

 

[elsteff1385]

Based upon DTCs changing and moving about, i would have recommended to check the age and condition of the 12V battery to ensure that it is good and strong, since an old, weak or worn out battery can cause a multitude of DTCs.

But someone has been messing with the OBC. It doesn't look like the relay or ceramic resistor has been changed to me.

I did this.

I hooked up a starter booster parallel to the battery to make sure it would not read flat or low voltage. I then diagnosed via the Mitsubishi interface. That all seems to work correctly.

The behaviour in charging did not change at all. Upon plugging in, charging LED lights up for about 10 seconds, while the fans in the back can be heard. As 10 seconds pass, the charge LED disappears and the fans stop.

From what i can tell, in the space between the PCB and the waffle, the ceramic power resistor has 100% sure been changed. I can see the pins heavily bent (very professional, yet again) and then soldered. I can also tell by looking at the bottom of the top PCB. it has small burn/scorch marks.

The relay is also 100% replaced. I can see big blobs of solder on the relay pins.

I'll try to study the existing info on the forum further to find out more.

 

[kiev]

Okay you have eyes on it to know for sure.

The lack of thermal paste: the housing is machined to a mirror finish, but the waffle plate is not. The best heat transfer is metal to metal, but any air gaps are not good, hence the addition of paste. But it should be a very thin layer just to fill microscopic air gaps as excess defeats the purpose; paste is better than air but still not great compared to metal.

i have no idea what they were trying to do with the little jumper wires under the power board.

Finding a used OBC might be a wise investment.