not charging my iON, cell or CMU or BMU problems

[tinoale]

About that, what is the exact purpose of this battery age value in the BMU ?

Some have noticed that they could reach 0% of SoC while the lowest cell voltage is still relatively high (3.2V for instance). Thus, not really using the whole battery capacity that they have available.
They suggest that resetting the age value will force the BMU to re-learn the actual capacity of the battery based solely on cells voltage.
This will make the car overestimate the available capacity for a little while, as long as the car learns the actual capacity.

What do you think ?

BTW I have apparently (by mistake) done just that. I went in BMU menus (Diagbox) looking for that option. I did not go into all the screens so I did not think I had actually done anything but this morning I had 45.7Ah in CaniOn, so I guess I went one click too far :idea:
I had 33.7Ah right before.

Anyhow, it is done so... I guess I'll see how it goes from now.

 

[kiev]

That's amazing--we have to figure out what you did to get those results.

 

[DBMandrake]

About that, what is the exact purpose of this battery age value in the BMU ?

My guess is that when you replace the entire traction battery with a "new" one, you enter it's age so that the initial Ah capacity estimate is not that of a brand new battery but that of one that has sat in a warehouse for that amount of time.

Some have noticed that they could reach 0% of SoC while the lowest cell voltage is still relatively high (3.2V for instance). Thus, not really using the whole battery capacity that they have available.

I'm not sure that I'd call 3.2 volts relatively high. My car - at least back when I tested a full discharge when it had about 37Ah capacity, shut down completely at 3.63 volts/cell. Keep in mind that voltage falls much more quickly below about 20% SoC, so there is actually very little capacity between 3.63 volts and 3.2 volts - maybe 5% at most.

Also you have to allow for voltage drop under load. For example if you never want your cells to go below 3 volts at any time, discharging to 3.2 volts unloaded would give a voltage below 3 volts when loaded. So a higher cutoff voltage is used to allow for voltage drop under load to prevent the cells going under voltage when you accelerate.

They suggest that resetting the age value will force the BMU to re-learn the actual capacity of the battery based solely on cells voltage.
This will make the car overestimate the available capacity for a little while, as long as the car learns the actual capacity.

What do you think ?

BTW I have apparently (by mistake) done just that. I went in BMU menus (Diagbox) looking for that option. I did not go into all the screens so I did not think I had actually done anything but this morning I had 45.7Ah in CaniOn, so I guess I went one click too far :idea:
I had 33.7Ah right before.

Anyhow, it is done so... I guess I'll see how it goes from now.

That's amazing--we have to figure out what you did to get those results.

Resetting the BMU's Ah estimate is easy - I've just done it on my car to run the same experiment. (Because, why not ? )

I took screenshots but since it's a PITA to attach images to this forum I'll just describe it.

In the repair section you go into the BMU, in the maintenance procedures there is one "Traction Battery Replacement Procedure". Running this just takes seconds and at the end of it the Ah capacity reported in Canion jumped up from 34.0 to 45.8Ah.

So I guess that answers the age old question of what is the capacity of a new battery in these - according to the BMS when reset it's 45.8Ah !!! This is very close to the 46Ah I had estimated via other means so I'm chuffed with that... Interestingly in the first few minutes the figure dropped to 45.6 and then 45.3 - this with the car just sitting on the driveway and the key being turned on and off a few times, but it seems to be steady at 45.3 now - until I drive it, when it will no doubt make a large downwards correction. (it's currently charging to 100% and will be used again later today)

Of course the car is now greatly over estimating the usable capacity of the battery which means I need to be careful with my range as "unexpected" appearance of the tortoise is very likely near it's true range when the BMS gets a wake up call... so I'm going to monitor every driving session for the next few days with Canion to see what happens with the Ah figure and how often and when it makes corrections.

Interestingly after running the battery swap procedure it tells you:

"If the new traction battery was manufactured more than 3 months ago, carry out the traction battery maintenance procedure the date of production of the battery is indicated at the rear of the traction battery and is accessible through the rear LH wheel arch".

I've run the traction battery maintenance procedure once before and I don't remember it asking for a manufacture date of the battery.

The maintenance procedure is very simple and it basically just instructs you to turn the car on and set the heating to maximum and wait until "a" cell voltage is between 3.75v and 3.775 volts, (which is approx 20% SoC) then gets you to plug the charger in to do a 100% charge - at the end of that a correction is made to the Ah figure.

Back when I ran this I was already seeing more rapid degradation of my battery, and the figure went down from 37.6Ah before the test to 36.1Ah after the test :? although it did rebound by itself to 37.1Ah about 400 miles later...

Interestingly today I noticed a page in the BMU called "BMU capacity after maintenance". This has many rows of "Maximum capacity of the cells after the last traction battery maintenance" and "Minimum capacity of the cells after the last traction battery maintenance".

For the first pair it gives 41.0Ah for maximum capacity and 38.1Ah for minimum capacity - this will have been recorded during the same test where it adjusted the usable Ah capacity to 36.1Ah and then rebounded to 37.1Ah. The remaining rows are all zero which presumably means the test has never been run before in the life of the car.

So my interpretation of this is that running the battery maintenance routine measures the spread of cell capacity from the worst to best cell, and at that time (more than a year ago) there was already a 3Ah spread. I'd love to know what the spread is now, so I might try running the test again next weekend. (As it takes nearly a whole day to run counting discharging and charging, and I need to use the car this weekend...)

One thing we've learnt from this is that it's unfortunately very easy to temporarily fudge the Ah capacity to a high value by using a diagnostic tool, just like you can on a Leaf, which means it's something unscrupulous sellers could do...

 

[kiev]

Thank you Simon that is very informative. As far as i know, nobody over here has a real MUT that will perform these tasks such as your Diagbox tool.

Are you able to call up individual data list items or does it just give the entire list? For example items 56 and 57 deal with the eprom.

ref: CMU DATA ITEM LIST, http://mmc-manuals.ru/manuals/i-miev/online/Service_Manual/2012/54/html/M154945510002500ENG.HTM

p.s. As far as the "learning value" age in months, i would guess it is used for warranty claims purposes

 

[DBMandrake]

Thank you Simon that is very informative. As far as i know, nobody over here has a real MUT that will perform these tasks such as your Diagbox tool.

Are you able to call up individual data list items or does it just give the entire list? For example items 56 and 57 deal with the eprom.

ref: CMU DATA ITEM LIST, http://mmc-manuals.ru/manuals/i-miev/online/Service_Manual/2012/54/html/M154945510002500ENG.HTM

There are two pages that show the lists you show yes, but you can't go any further into the individual items, they are just a list with parameter name and value. For example the EEPROM will just say normal or abnormal. It lists them as EEPROM 1 and EEPROM 2 however, and the first EEPROM says abnormal on all my CMU's and Normal for the second EEPROM - no idea the significance of this.

If you look at Rupert's 10 May diagnostic zip file at cmu08 etat.fr.en.pdf it will show the list you're referring to already translated (poorly!) to english. cmu08 tension.fr.en.pdf shows the second table you list with the voltages.

p.s. As far as the "learning value" age in months, i would guess it is used for warranty claims purposes

I can't find anywhere to enter a battery pack age even when telling it that the battery has been replaced. All it says is if the battery is over 3 months old when fitting to run a calibration... so I'm not convinced there even is a place to enter a battery age.

 

[DBMandrake]

BTW I have apparently (by mistake) done just that. I went in BMU menus (Diagbox) looking for that option. I did not go into all the screens so I did not think I had actually done anything but this morning I had 45.7Ah in CaniOn, so I guess I went one click too far :idea:
I had 33.7Ah right before.

Anyhow, it is done so... I guess I'll see how it goes from now.

That's amazing--we have to figure out what you did to get those results.

Resetting the BMU's Ah estimate is easy - I've just done it on my car to run the same experiment. (Because, why not ? )

WARNING, WARNING, WARNING! :shock:

Despite thinking I was well prepared I nearly ended up stranding myself half a mile from home due to resetting the battery capacity.

I had been out and back running errands having done a total of 40 miles and the car was reporting a no doubt very optimistic (due to the reset) range remaining of 25 miles implying a total range of 65 miles.

So I equipped myself with two 15 metre extension reels, the granny charger, laptop with Diagbox and Canion and set off to carefully drive out the remaining range in ever decreasing circles around my neighbourhood as the battery ticked down.

A year ago when I did a run flat test the car reached 10% SoC at 330 volts at which point the tortoise light came on, however I was able to drive about another 4 miles before any reduction in power. I then parked the car on the driveway with the heater on and left it and found that the high voltage system shut down completely and would not come back on once it reached 320 volts. So 320 volts was the cutoff voltage back then.

Today the BMS allowed the voltage to go far below that. It was still driving with no tortoise light or reduction in power as low as 310 volts.

However not long after that when I tried to accelerate there was a "stumble" and the tortoise light flicked on then went off when eased up on the accelerator. I was only about a mile from home so I thought I'd be OK, so I turned around and drove carefully towards home..... for about 200 metres before almost all power was removed! The car slowed right down to 7 mph so I was trying to creep along on the side of the road desperately trying to make it to a slight crest so that I could coast the rest of the way down the hill to our house in Neutral.

I barely made it. Despite being limited to 7mph the car was still cheerfully reporting 1 bar and Canion reported 15%!

From the first stumble when accelerating until being restricted to 7 mph was only a couple of hundred meters, not the usual several miles warning you get in tortoise mode. I noticed that tortoise mode would flash on when the weakest cell got below about 3 volts but then go back off again when I eased off the accelerator. (At least for a while)

So my conclusion from this is that there are actually two separate and distinct triggers for the tortoise light.

1) When the calculated SoC gets below about 10% the light comes on and stays on but acceleration is not restricted. When you get to 0% the car just stops.

2) When the instantaneous voltage of any cell goes below about 3 volts under load power is immediately restricted to a very low level, however if you ease off and voltage goes above 3 volts again the light goes back out.

Because the SoC estimate was wildly optimistic (about 20% higher than the "real" value) the BMS just let the car keep driving until the 3v cutout threshold was reached. Normally this would never happen because it would hit a calculated 10% SoC well before then.

So watch out tinoale - if you try to drive it right down to tortoise mode like I did after the Ah reset you'll probably find yourself phoning recovery services - I was VERY lucky that I was so close to home with a down hill to coast down half the way or I would have had to phone for recovery for sure. Unlike normal tortoise mode that gives you a few miles warning and lets you drive at normal speed, this tortoise mode limited me to 7mph and probably would have done half a mile at most.

It will be interesting to see what Ah capacity is reported after a full charge - it was still cheerfully reported 45.3 Ah before I plugged it in, so it apparently makes Ah corrections during charge rather than discharge...

 

[kiev]

Wow what a great experience you've had--thanks for sharing the story, and thank goodness you went out prepared with extension cords and level I, even if not needed. You are definitely exploring new territory of these packs and cars, and every little bit helps understand what they do and how they work...

 

[DBMandrake]

Wow what a great experience you've had--thanks for sharing the story, and thank goodness you went out prepared with extension cords and level I, even if not needed. You are definitely exploring new territory of these packs and cars, and every little bit helps understand what they do and how they work...

Great experience is not quite the wording I would have used. :lol:

Well it finally finished charging after an extra long charging session - with a long period of balancing at the end where it pulled my two weakest cells (25 and 70) down at the end as they reached full charge voltage first.

It stopped at "97%" indicated SoC, and reports a hilarious 85 miles of range :lol: but has still not updated the Ah estimate which is still on 45.3Ah.... :?

Which means next time I drive the car I have the risk of reaching turtle mode unexpectedly like I did today. I wonder how quickly it will adapt the Ah figure ?

I know if I run the battery calibration it will do it within the one charging cycle, but I'm tempted to let it go and see how long it takes to figure out the difference...

 

[tinoale]

Hi,

I also believe we don't quite understand how the car estimates and/or updated the SOH of the battery.

When you cleared the Ah value which initially went back to 45+ Ah, then hit a very low actual SOH indicated by cells voltage, I don't quite understand why the car did not instantly update the Ah value of your pack. Why is it still 45+ Ah after recharge and how long is the car going to take to update that value, that's pretty unclear. You could run into a very low cell voltage again which is silly...

So when I accidentally reset the Ah value of my pack, it showed a whooping 45.7Ah value. I had 33.7Ah before.
I was tempted to let the car update capacity value by itself, little by little, out of curiosity, while being careful to avoid a distress situation.
But I was also curious about the capacity test and thought I wanted to update that value once and for all.
Chew on it a bit then decided I wanted to run a battery capacity test so I tried it.

The test went well. I carefully drove until I had 2 bars left. Headed back home. Started the procedure, which used the heater to deplete the battery. I don't know what the lowest cell voltage was when the heater automatically stopped and the charge started, gauge was showing 1 bar when that happened. I did not plug CaniOn while the test was running. I can only assume a given cell voltage triggered the start of the charge.
I let the car do it's full charge. Next day, I read 13kWh from my TP-Link HS110 monitoring. Then started the car and plugged Diagbox. Tried to read the tests results but a "communication error" prevents me from reading the official test results. Duh !

Went to read the Ah value and it was updated to 32.7Ah. I guess that's the test result that I wanted.

Apparently, the test did force an update of the Ah value which is good to know. I will let the car update it by itself from now on, will keep en eye on it in Canion. May be run another capacity test in a few months.

Now, I wonder if I did not reset my Ah pack value prior to the capacity test, would the result be any different ? I have no idea.

If you accidentally erase that value like I did, I do recommend a capacity test to force an update of the estimated Ah. Now my car displays 90+ km left when fully charged but if that's only the truth then so be it. I only need 50km of actual range in winter to keep using it 12.000km a year.

 

[DBMandrake]

I spent most of today trying to perform the battery calibration without success. I've done the calibration before so I'm not entirely sure why it refused this time...

First I discharged the battery to 3.76v for the lowest cell voltage - Ah capacity remained at 45.1Ah and did not update.

Step one of the calibration process seems to reset the SoC. (not SoH) Before step one it was reporting the battery was still about 30% SoC and about 4 bars, after step one was completed the SoC dropped to 15% and one bar flashing. I assume this is done by using voltage estimation, which can be done at a low voltage like 3.75 - 3.775.

It then tells you to turn off the key and wait an hour before doing step 2 - which you can't bypass. (I tried tweaking the clock in the laptop but it didn't work... :mrgreen: )

So after an hour I go to step 2 and I get "Preparation to measure the traction battery state of health has failed. The traction battery charge status does not permit starting of the procedure".

At this low SoC my two weak cells are over 100mV below the highest cells, so I assume that the divergence in cell voltage is too great for the test to start, as most of the cells were above the allowable voltage range. I then tried discharging the battery further until the high cells were within the correct voltage range and the lowest cells were below it, waited the hour, tried to start it again - failed.

So I am unable to start step two of the test because it is apparently unhappy with the spread of voltages of the cells at the start of the test - nothing I can do about that! :evil:

So I just let it charge up normally, it stopped at a reported 96% and still remains at 45.1Ah, so it has not learnt yet that the capacity of the cells is well below what it thinks. Also the SoC suddenly jumped from 82% to 92% during the charging process (probably due to top end voltage estimation kicking in) and despite that it didn't adjust the Ah capacity.

So I kind of wish I hadn't touched it now. I'm still going to have to drive carefully and keep in mind the reported range is about 15 miles further than my real range or I could find myself at risk of stranding again.

When I get home from work tomorrow night if the voltage is near the correct voltage range I'm going to have another go at starting the calibration.

 

[DBMandrake]

Better luck tonight - I got past step 2 and think I know what I did wrong last time, so the car is now charging on the final phase of the battery calibration. Unfortunately that will take about 4 hours so will be midnight before it finishes!

So I won't find out the result until the morning. Assuming it works I'll post the steps that I followed this time.

 

[DBMandrake]

I also believe we don't quite understand how the car estimates and/or updated the SOH of the battery.

When you cleared the Ah value which initially went back to 45+ Ah, then hit a very low actual SOH indicated by cells voltage, I don't quite understand why the car did not instantly update the Ah value of your pack. Why is it still 45+ Ah after recharge and how long is the car going to take to update that value, that's pretty unclear. You could run into a very low cell voltage again which is silly...

I suspect the BMS is deliberately programmed to be "suspicious" of any apparent large change in usable Ah capacity of the battery, (especially from 46Ah to 33Ah!) and only make a large change after multiple confirmations to ensure that one bad reading doesn't thrown it completely out. After all usable Ah capacity is only supposed to change very slowly (over months) even with an iffy battery let alone a healthy one.

Now, I wonder if I did not reset my Ah pack value prior to the capacity test, would the result be any different ? I have no idea.

I don't think resetting it or not would have made any difference.

If you accidentally erase that value like I did, I do recommend a capacity test to force an update of the estimated Ah. Now my car displays 90+ km left when fully charged but if that's only the truth then so be it. I only need 50km of actual range in winter to keep using it 12.000km a year.

I agree - it could take hundreds of miles of driving for the car to automatically adapt to the true lower capacity after a reset to 46Ah - during which time the BMS is allowing over discharge of the cells (at least compared to the normal limits) and you are at risk of being caught out and getting stranded as I almost was.

I can't think of a good reason to do the full reset unless you were actually replacing the entire pack. If you are just replacing a few dud cells or just want it to re-measure the true state of the battery the battery calibration should be more than sufficient - provided it is willing to learn an increase in Ah capacity not just a decrease. (Which we don't know at the moment, but I think it probably does)

 

[DBMandrake]

Calibration Success! It is now reporting 33.0Ah instead of 45.1Ah... indicated full charge range has dropped by a full 17 miles from 70 miles to 53 miles, which is spot on what I actually get with combined cycle driving with the degree of battery degradation the car has. So basically with a battery that has degraded to just above 70% SoH the car has lost 17 miles of range since it was brand new...(but probably about 5-8 miles since I've had it)

So here is the process and what I did right and wrong. Step 1:

After this is a screen telling you that the battery should be discharged to "approximately 4 bars" before proceeding to the next step. When you acknowledge that screen the reported SoC instantly jumps to a new value - my assumption is that a voltage estimation of the SoC is done and the figure updated at that point. So in the case of the real Ah capacity being a lot lower than what it thought, the SoC jumped from around 40% to 15%.

You then have a forced wait period of one hour before you can proceed to step 2:

The next screen is:

This is where things started to go wrong... Because I already knew the target cell voltage range was 3.750 to 3.775 volts, I had already discharged the car to this range before starting step 2. Big mistake, because acknowledging the page just gave me this cryptic error:

I tried a couple of times slightly discharging the car below the range then back up, or charging it above and then back down, no luck!

I noticed that the voltage of the "minimum cell voltage" did not update in real time when it was below or within the range, only when it was above the range - and also that the button in the bottom right doesn't appear when the voltage is too high...

Thinking about the comment of "approximately 4 bars", which is quite a bit above 3.775 volts I realised that the problem was that it expects you to start with the voltage above 3.775 volts, turn the heater on and leave it sitting on this page...

Starting at 4 bars wouldn't actually work because with the gross over estimation of the capacity of the battery 4 bars was actually less than the target voltage range... :twisted:

So in the end what I did was to charge/discharge the battery until the lowest cell was about 3.85 volts - or 100mV above the top of the target range (as monitored in Canion) and then go to step one, wait then hour, then start step 2 and turn on the heater to start discharging it as seen below. Note the lack of acknowledge button in the bottom right corner:

The minimum cell voltage figure updates in realtime so you just wait until this dips into the specified range for a few minutes and then you will get the acknowledge button in the bottom right corner to proceed. At that point you turn off the heater.

You then get this screen:

At this point you plug the car into charge. My suspicion is that completing this step tells the BMS that it is about to do a calibration charge and to believe whatever result it gets, no matter how much it differs from the current Ah estimate. In other words not be sceptical about a large change.

At the end of the charging session the Ah capacity figure has still not been updated yet! You then move on to step three, which I forgot to take a screenshot of which just tells you to turn the key on and acknowledge the messages, at that point the Ah figure is finally updated to the new measured value, which is 33.0Ah - 1Ah less than what I had before.

Last time I did the battery calibration I saw a similar drop and then a 1Ah rebound a few days latter so my guess is that the calibration is just very conservative and likes to leave some margin.

After the test is done there is another very interesting place you can optionally look, under "capacity after maintenance", which I think is under the "traceability of the maintenance" section of the BMS:

What's cool about this is it appears to show the spread of Ah capacity between the worst and best cells. As you can see here it says my best cell is still 40.5Ah while the worst one is 34.8Ah - a large 5.7Ah spread....

I happened to save a copy of my previous calibration result from about a year (and 12k miles ago) ago below:

Not nearly as much spread there, so my suspicions that some cells are degrading at a faster rate than others is confirmed. The best cells have only degraded by 0.5Ah in the last 12k miles while the worst have degraded by 3.3Ah or about 6 times faster!

I was expecting to see the previous values logged in the report but realised that the battery replacement procedure no doubt wipes any previous service history for the battery including the previous battery capacity maintenance values. So another reason not to do a full reset! Just do the battery calibration only.

@tinoale: Can you have a look at the "bmu capacity after maintenance" screen on your car ? It's under the BMU in the "traceability of the maintenance" section, and is a quick read only report that doesn't change anything.

I'd be curious to see what your cell spread is compared to mine. The reason cell spread is useful is because if Ah capacity is low but there is a narrow cell spread then all cells are degraded by about the same amount so replacing a few individual cells would not give any benefit.

However if there is a very wide spread of capacity between cells - as in my case, and only a small handful of cells are low performing - as in my case, then replacement of just a few cells could potentially restore a lot of lost capacity...

I'll save a full analysis of my recent battery tests for my own battery thread over here:

http://myimiev.com/forum/viewtopic.php?f=23&t=4014&start=50#p39013

 

[tinoale]

Hi

I have Diagbox v7.1 only and the calibration menu for my C-zero is clearly different from yours

My calibration only has 2 steps:
Step one, start with more than 1 bar, turn The heater on, switch the car off, plug the charger in. Charge does’t start yet.

If draws power until it automatically stops and start charging by itself. It then does a full charge.

When it is done i’m Supposed to check the result in a step 2 menu but when I try to access the menu there’s a error. So I can’t check the best and worst values... just the available Ah which is updated after the test.

My c-zero is 90000km, 2011, 16kwh
Reporting 32,7Ah after the calibration.

I have a Canion capture from before the calibration when the voltage dropped really low : 8% soc (probably very wrong as not calibrated), lowest cell 3.205V, highest cell 3.580, spread 0.375V

Not sure if such a spread is normal but the actual SoC must have been awefully low. I guess I should check the spread next time I hit a “calibrated” 10% SoC...

 

[tinoale]

Another data point, not sure if that was before or after the Ah erase (probably before) :
Odo 87856
SoC 15,5
Lowest 3,655
Highest 3,730
Spread 0,075

Definitely before I touched anything with diagbox :
Odo 61164
SoC 10,5
Lowest 3,435
Highest 3,605
Spread 0,170

 

[DBMandrake]

I've been reading the CMU firmware. ... 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).

Automatic numbering like this seems unlikely - by what mechanism would they acquire consistent numbering when they left the factory ?

If I'm right, they acquire their IDs, possibly every time they are reset, by their position in a daisy chain of special signals for that purpose:

I'll be the first to admit that the details on this drawing are staggeringly light. It's a study in minimality.

I've been giving some thought to this whole CMU numbering conundrum and I think I've worked out the most likely way this is done.

I don't think it happens automatically on the fly because I'm sure there is a thread on here somewhere where someone swapped two CMU's and the numbering of the CMU's went with the boards.

However if we assume the renumbering is not automatic and needs to be triggered somehow - I bet that the "battery replacement procedure" - the one I ran recently which reset the capacity to 45.8Ah also triggers an automatic numbering of the CMU units and stores their CAN bus ID's in the BMU.

It makes logical sense for this to be the case because this is the procedure you run immediately after replacing the whole traction battery, and that of course means that all CMU's are new to the car and to the BMU - which has remained with the car.

We know for sure the battery replacement procedure resets the capacity to about 45.8Ah and also that it clears the saved results of any previous battery calibrations. The old BMU needs to become acquainted with the numbering of the 12 new CMU's, so I bet this is also performed during this battery replacement procedure.

There is also a BMU replacement procedure which does much the same thing in case the BMU is replaced, so I suspect that must also do the re-numbering since the CMU's are new to THIS BMU...

So if my theory is right you could take any CMU and fit it to any location without any modifications, provided that you follow either the battery replacement procedure or the BMU replacement procedure in Diagbox to trigger a renumbering of the CMU's.

And after that you would have to do the battery calibration as well to get the Ah figure back to what it was before. (At least if you do the battery replacement procedure - from memory I think the BMU replacement procedure might allow you to save the Ah figure from the old BMU and enter it into the new one ?)

If you're only replacing a CMU it's unclear whether it would be better to use the battery replacement procedure or the BMU replacement procedure. Although I looked at the BMU replacement procedure I didn't actually go through with it so I don't know what other consequences it might have, whereas I do know for sure what the battery replacement procedure did.

I don't have any way to prove any of this numbering theory of course.

One question I have - does the BMU just "learn" the Can BUS ID's of the CMU's or does the BMU *program* the Canbus ID's of the CMU's during this numbering process ?

It would seem to be easier for the BMU to just learn the CAN bus ID's of the CMU's however this seems to be the less likely method because (a) all CMU's would have to be made with random non-clashing CAN bus ID's, and (b) programs like Canion would not know which CMU was which unless that information could be extracted from the BMU first ?

The other alternative is the BMU programs the CAN bus ID's into the CMU's, however that then requires storage in the CMU for the ID to be saved - does it get saved in the EEPROM ?

The second theory - that the BMU programs the CAN bus numbers of the CMU's to standardised numbers for each location and saves it to non-volatile storage in the CMU seems to fit the evidence far better.

 

[coulomb]

The second theory - that the BMU programs the CAN bus numbers of the CMU's to standardised numbers for each location and saves it to non-volatile storage in the CMU seems to fit the evidence far better.

Yes, except that the CAN bus IDs (there are several per CMU) can be and are calculated from the CMU ID. All the CMU needs to know is a number from 1-12.

From hazy memory, the CMU firmware increments a variable under certain conditions, like when it receives a certain pattern on a serial port of some sort, and something tells it that now it needs to stop incrementing, and that number becomes the CMU ID. It has something to do with the delay between ID in and ID out, and the number of zeros that turn up on a serial port.

I imagine that this number (the CMU ID) is stored in Eeprom, but I still haven't found where the Eeprom is accessed. But remember that the RAM in the CMU is battery backed up, so it's effectively non-volatile.

 

[martinwinlow]

Hi all,

Just reading this thread as I'm about to open my battery box after successfully removing it from my 2009 i-MiEV following what appears to be another CMU LTC chip failure (see https://www.speakev.com/threads/i-miev-with-failing-battery-another-cmu-ltc-chip-failure.144620/page-2#post-2828186).

I have a spare BMU PCB obtained from ebay seller jmeuk (www.secondlifestorage.com - cell-block number unknown) along with 2 spare cells. I plan on swapping out my defective CMU PCB with the spare and attempting to re-program its 'daisy-chain' number using the MUT 3 by means of the 'battery replacement procedure' followed by a battery recalibration using the same tool. Of course, it may by coincidence be the correctly numbered cell-block PCB in the first place. Hmmm...

 

[kiev]

don't know if this would help you, but we had some discussion about the eeprom chip on the CMU boards, including a download of the contents here:
http://myimiev.com/forum/viewtopic.php?f=23&t=4302&p=39921&hilit=CMU+eprom#p39918

 

[martinwinlow]

I appear today to have confirmed that the MUT3 can renumber CMU BMS PCBs but I have yet to put the car back together again sufficiently to confirm (by seeing if it charges and runs - albeit with the battery still only temporarily attached). Please see https://www.speakev.com/threads/i-miev-with-failing-battery-another-cmu-ltc-chip-failure.144620/page-2 for more details.