not charging my iON, cell or CMU or BMU problems

[doanabogdan]

http://myimiev.com/forum/viewtopic.php?f=23&t=3897

 

[tinoale]

Tinoale, glad the problem has gone away (at least, for the time being).

Very disconcerting about the dramatic loss in range - especially with the heater OFF. More confusing is the slow drop on the evening return trip. And, they average out to normal for the round trip?

From my perspective, your video did not demonstrate an unusual situation, as the the bars hop around as the car discharges and is no longer sitting at 100%SoC. I would be tempted to simply plug the car in and let it fully fully charge up and go through the balancing cycle, perhaps a couple of times.

At this point in time, there could be many sources of the problem and your speculations are but some of the ideas. I would simply continue using the car normally until it starts to repeatedly demonstrate something - for this, CaniOn is invaluable.

Sorry, I can't offer any concrete suggestions.

Did you watch the video carefully ?
happens at 00:04, 00:10 and 00:22 : cell #77 voltage drops just for an instant.

Definetely unusual and not normal at all. It is like for an instant, the reported voltage of one cell (and always that one 77) is completely off by some large amount.

In the morning the gauge would drop very very quickly. The BMU sees one cell with a low reported voltage but just seconds at a time. I don't know how it computes that information exactly, but it does lowers it's estimate of the whole pack SOC accordingly.

In the evening, the issue is gone but at the same time, there are probably safeguard in the BMU programming to prevent showing increasing SOC without power input (from charging or from regen). So the SOC would just stay there while driving until the actual SOC would really go down.

When I got back home in the evening the SOC was as usual, and I have all reasons to believe that the SOC issue only existed in the morning and the evening drive just compensated for it...

Another cold wave is coming our way, maybe it will start acting up again, this time I will try to isolate the issue to temperature only if I have enough time.

 

[tinoale]

Update,

Again the issue appeared after a sub-zero °C night and a full battery.

Did not have the chance to test a cold night and a partially discharged battery. Thus I can't determine if the temperature is the sole factor or if it is a combination of the cold AND a full SOC that creates the issue.

But the behavior was consistent with what I have seen previously. At least it is consistent and repeatable. And always on the same cell #77.

 

[tinoale]

Update again.

So after my last message in march 2018 the problem simply disappeared and I did not get a single glitch in months.
Until temperature dropped again around 5°C a few weeks back.

With Canion this time I noticed more than one cell was acting up. Dropping from around 4+ volts down to 3.870V and back up. I noticed 3 cells doing this, although one was doing it way more than the others. BTW I noticed I mistakenly talked about cell 77 previously in fact it was cell #71. Cells 73 and 74 also acted up, they are all within the same module.

My conclusions at this point was :
- problem is temperature related, 100% sure
- problem seems confined within module CMU10
- problem probably within the analog section of the CMU10 board (cracked solder joints, or analog-to-digital component LTC6802 failing)

Temperature went back up, battery continued to show the behavior until temp went above 10°C when it stopped again. So, there is some kind of hysteresis behavior related to temperature.

That was until today.

Again, temps went down as low as sub 5°C. When trying to drive, after a very short while, battery SOC went straight down to 0 (no bar at all) along with the exclamation mark.

Pulled Canion, reset the car, this is when things changed from the previously described behavior :
- during the brief time the car is showing a SOC and exclamation mark not on, I read normal cells voltages. NO drop as seen before.
- after a short while (maybe 10-15 sec) the SOC drops to 0 and exclamation mark turns on : I instantly lose Canion readings


Turning the car off then on reset the SOC to the previous number of bars minus 1 bar. Needless to say, I didn't take long to reach 0 bars. And the car won't charge in that state (which is a non issue by itself considering the actual SOC is in fact nearly full).

Now I'm having a hard time interpreting this new behavior ! Until now I was assuming the LTC6802 was the culpit, that or a cracked capacitor or cracked solder joints. Basically anything that could produce false voltage readings on cells and trump the BMU which would lower the SOC reading.

Loosing the SOC entirely with no anomaly on the cells voltage readings makes me think something else (something more ?) is faulty.

What if it was the CMU master component (the one that stores the VIN and communicates with the BMU ) that was failing since the beginning ? could it explain both the previous behavior as well as the new one ?

Kinda lost here !! I've got one big paper weight now

 

[kiev]

...Loosing the SOC entirely with no anomaly on the cells voltage readings makes me think something else (something more ?) is faulty.

What if it was the CMU master component (the one that stores the VIN and communicates with the BMU ) that was failing since the beginning ? could it explain both the previous behavior as well as the new one ?

The CMU master is the BMU located under the rear seat. It could be the culprit, but why would it only show as affecting CMU10 and not all the modules?

What is the age and condition of your 12V Aux battery? An old, weak or worn out aux battery can cause a multitude of problems across various systems on these cars.

i tend to agree with your assessment that there is a temperature-related element to this issue, and a bad solder joint is a prime possibility. Maybe you could park in a warm garage and use a space heater to heat up the pack to see if something changes. And maybe remove the rear seat and heat up the BMU if you think the issue is there.

 

[tinoale]

Hi !

I forgot to mention that in order to rule out a bad 12V battery, I have hooked up a new 12V battery in parallel to the original one.
Resting voltage was nearly 13V as it is brand new and well charged.

That didn't make any difference (I sure wish it did!)

I'm going to need to check how to access the BMU under the read seats.

Until the recent behaviors everything was consistent with a defect on the CMU10 board but with the latest behavior, I am not sure really what to think anymore ! :,/

 

[tinoale]

BTW I can't help but notice I seemingly have an issue with CMU10, the same as the one the OP has an issue with... coincidence or ?

 

[kiev]

That does seem to be an unusual coincidence.

The CMU master component (a microcontroller chip) is shown near the top of the photo on page 2. There are also 4 aluminum electrolytic capacitor not shown in that photo. Plus numerous tiny ceramic chip capacitors. Failure of any of those, such as a hairline fracture in the ceramic, could disrupt the proper operation of the board.

In my experience the ceramic caps are difficult intermittent culprits and require a temperature change to detect. They can be working, then apply some heat or cold, and they short. Then the temperature changes back and they work again--very frustrating to troubleshoot.

With the complete collapse of the SOC there is likely a new or different DTC thrown, which may give some clue if you can get a readout.

So need to look for DTC codes stored in the EV-ECU related to the BMU, e.g. loss of CAN, low supply voltage, abnormal cell count, etc.

 

[Gary12345]

Hi guys,

Just to add, I am also experiencing fluctuating voltage readings on one battery pack and it is also CMU 10 ! Is there something about the placement of module 10 which causes this issue?

And did you guys ever manage to fix the circuit board? I have not yet got the board out to inspect so I don't yet know if there is obvious component failure however in my case the voltage is bouncing around all the time for all cells on this board - canion could not even graph it, but i can see it on the icarsoft i909.

Thanks,

Gary.

 

[tinoale]

Hi !

My issue that started only in cold weather is now permanent.
Heating the battery and erasing all error codes with Diagbox (PSA tool) I could restart the car, but the voltage readings on CMU_10 are still jumping all over the place on 3-4 cells of the module.
Not bad enough to completely disable the car (like it was during this winter) but still errorous and unreliable.

Those issues on CMU_10 can't be a coincidence, maybe it is the board that sees the most temperature cycles, thus fails most of the time ? Hard to tell.

Anyhow, I might have found a company that could repair my battery.
Since the car would need to be transported over several hundred km, I really need to know this is going to work before I give it a go...

In this thread, it was said a CMU board needs to be programmed to learn the cells modules it is supervising. The repair guy says that if we're going to swap the CMU_10 board we need to source a used CMU_10 board (not another number). So about that, it matches the idea that CMU boards are programmed and apparently cannot be reprogrammed.

On the other hand, he is not aware of the fact that the CMU board is VIN programmed. In other words, a CMU_x board from a used vehicle could be used as is in any other vehicle, as long as it is replacing a CMU_x board (not a CMU_y or CMU_z...). If the module number matches, it should be fine he reckons.

Does anyone has a verified information about that question. Are CMU boards VIN programmed or not ? Are they car swappable if CMU module number matches ?

Cheers and good luck

 

[tinoale]

BTW the errors codes I pulled :


BMU :
P1A7F and P1A4B

EV ECU :
P1A39
P1A33
P1A2F
U1113

I also has some CAN bus error codes (lack of communication or communication errors) but the repair guy said we should not worry too much about them, as a weak 12V battery can make them pop up.

Those I noted here are the ones that come back quickly

 

[coulomb]

The repair guy says that if we're going to swap the CMU_10 board we need to source a used CMU_10 board (not another number).

I've been reading the CMU firmware. It's hard going for me, but there is definitely a mechanism for "numbering" the CMUs. In fact, it seems to me that this happens automatically any time that there is a certain type of error (I can't be certain about what type of error, and it was some time ago I that I found this). But I have no idea how to trigger this process if needed. [ Edit: It's possible that the CMUs will detect say two CMU 5s and/or no CMU 10, and that this mismatch will automatically trigger the renumbering process. It has to originate from the BMU. ]

So my conclusion is that you don't have to get a particular numbered CMU board, but I don't know how to make the renumbering happen. Perhaps there is a function on the MUT-3 that triggers it. Or some special CAN bus message.

Of course, you'll need an 8-cell board, not a 4-cell board, so it can't be from a CMU 6 or 12 (those are the 4-cell boards).

Not much help I know, but it might be able to be pieced together with other clues.

 

[kiev]

The is a reference to cell numbering in the description of the BMU pins 48 and 49:

1 Auxiliary battery power source
2 EV-ECU control power source
3 BMU earth
6 CAN interface (high)
7 CAN interface (low)
8 K-LINE
12 Main battery cooling fan relay
13 Main battery cooling fan PWM signal
21 Input signal for main battery cooling fan speed
31 Applied voltage for main battery current sensor
32 Main battery current sensor (high)
33 Main battery current sensor (low)
35 Main battery earth leakage sensor
37 Local CAN (for main battery) interface (high)
38 Local CAN (for main battery) interface (low)
42 Main battery current sensor earth
43 Main battery current sensor earth (shielded)
46 Main battery earth leakage sensor pre-check signal
48 CMU ID automatic number input signal
49 CMU ID automatic number output signal

 

[tinoale]

Hi!

Super interesting info, would be cool to tinker with this. But I have found a CMU 10 board set (board, wiring and space board) of eBay though so apparently I won’t need this auto numbering function.

Have you any info about the CMU board being VIN programmed ?

 

[coulomb]

But I have found a CMU 10 board set (board, wiring and space board) of eBay though so apparently I won’t need this auto numbering function.

Oh, I forgot to mention that as far as I know, the ID resides in RAM. If so, all the 8-cell CMU boards would be the same, and you'll need it anyway. But there might be somewhere it reads that ID from, that I haven't noticed.

Have you any info about the CMU board being VIN programmed ?

I've not noticed anything [ edit: in the CMU firmware ] that I have associated with VIN numbers, but there are plenty of things I don't understand, one of which could be a VIN number. Others may have more direct information, like "I tried it and it didn't work till the dealer did some magic".

 

[Gary12345]

** Just realised this is a really old thread - note to anyone else reading!! **

Hi, i just fixed the same issue on my i-miev. It is failure of the voltage monitoring chip on one CMU, the board in one of the battery modules. Mine was also pack 10, so it seems these pack 10 chips like to die.

I got a new chip and took it to a mobile phone repair guy to get him to swap the chips, this saved any hassle with reprogramming the CMUs.

MUT 3 can do the reprogramming but this is hassle, it is much easier to get the chip replaced, if you look at the circuit board you will find chip LTC6802-G2. You need to get this chip replaced. I bought it from one of the electronics suppliers, I think it was Rapid Electronics.

Are you confident which is CMU10?

Also are you using an iCarSoft i909? This gives you an explanation for all the error codes, makes it much easier but the ones you give are almost exactly the same as I had.

Thanks,

Gary.

 

[tinoale]

Hi Gary

Good info, quite reassuring that the issue really seem to be confined within the CMU board.

I use DIAGBOX to say that it is CMU number 10 that is failing.
On Canion, I see voltage issues on cells number 71 72 73 74.

I do not know, as of now, where is this board physically located. Any pointer to this information would be greatly appreciated.

Anyhow I have found a CMU 10 board on eBay for a decent price. My idea at this point is to swap the whole CMU 10 board.

My problem now is to find someone willing to do the swap or let me use a garage spot for a day so I can do it. There is one company but far from where I am, transport and repair will cost me 1k€ overall.

How silly does it sound that the car is made useless because of a 10€ chip :roll:

Edit :
Gary do you confirm this is what you issue looked like : first at the beginning, second more recently (more severe) ?
https://youtu.be/VFCCpODjg-s
https://youtu.be/cuBEsbJZcg0

 

[kiev]

The LTC6802 cell monitoring chip does not have direct access to the CAN buss and does not receive or store the CMU number. There is a microcontroller chip that communicates between the LTC chip and the BMU, and [edit: the CMU number is stored on an eprom on the board.] No VIN coding used or required.

If it is defective in reading a cell voltage, then it could be the source of an error or issue.

Was CMU 10 in the 2nd from the front right location as shown in this diagram?

@tinoale, so your cells have voltage jumping around intermittently. does it affect your range? can you still charge full up to 16 bars?

There are 2 circuit boards for the 8-cell CMUs and it appears that you have a bad reading on 2 cells from each board. It would great to inspect the bad boards after you swap them out to determine the root cause.

 

[Gary12345]

I do not know, as of now, where is this board physically located. Any pointer to this information would be greatly appreciated.

Hi,

Your videos show exactly the same issue as I had, where voltages jumped up and down, mine was also CMU10. I would not buy a replacement CMU, instead fix the one you have like I did, otherwise you may find that the board you buy will not communicate with the BMU, it may not really be number 10, etc, etc.

When you take the battery pack out, there are 10x 8-cell modules, (and also 2x 4-cell modules if its a 16kwh pack). Using the diagram that kiev posted, identify which is module 10.

Disconnect the little communications connector, take the bus bar off and get module 10 out, remove the metal end caps and metal cover, then pop off the plastic cover and you can see the CMU board - there is one of these on each battery module.

You will be able to see the LTC6802-G2 chip - can you order one of these and then get someone to swap it out (laptop/mobile phone repair guy?).

Please ensure you follow the mitsubishi safety instructions for safe removal of the battery pack - it also weighs 240kg but i did all this on my driveway with 2 jacks and concrete blocks !

Thanks.

 

[Gary12345]

Since it is likely you cannot see the failure (for me the chip looked fine but did not work properly) If you want to confirm that you have the correct battery module, just disconnect the little communications connector, then reconnect the battery pack multi plugs and check the battery voltages, the one that was jumping up and down will now have disappeared.

thanks.