I think it's just one bad cell...

[the8bitlegend]

I have yet to go through some of the smaller maintenance tasks with my recent MiEV purchase, like a new 12v aux battery, and I haven't given the car more than a full day on the charger to see if the cell will somehow reach the voltage of its comrades.
I did, however, buy an OBD MX+ and install OBDZero and CanIon on my Android, and was able to get what I hope is useful data, among a bunch of information I don't have a decent grasp on yet. I'm adding a couple of screenshots of the cells I'm working with.

In OBDZero, I can see that cell G of module 1 is sitting at 3.76v, and in CanIon, the same claim is made in regards to cell #7, which I'm guessing is the same one.

I was wondering if anyone on myimiev has been in a situation like this one, and what direction anyone might think I could start moving in terms of research and resourcing.

If I don't manage to somehow improve the range on this vehicle, I'll still be satisfied knowing I spent $1000 on something that can safely get me to work and back through winter this year while I save for something more substantial and reliable.

I appreciate this community's persistence. Thanks for reading!

 

[MickeyS70]

Hello and welcome to the forum

This issue is most likely caused by a CMU (cell management unit) problem i.e it’s not reading cell #7 voltage correctly.

To test this theory, take screen shots at various SoC levels and compare #7’s reported voltages to the others, if the difference remains constant, the LTC chip on CMU1 is probably faulty.

The traditional way to fix this problem is to take out and open up the HV pack and replace CMU1 (or just the chip on it) however there is an alternative:

https://myimiev.com/threads/cmu-can-‘spoofing’.5505/

Mickey

 

[the8bitlegend]

Hello and welcome to the forum

This issue is most likely caused by a CMU (cell management unit) problem i.e it’s not reading cell #7 voltage correctly.

To test this theory, take screen shots at various SoC levels and compare #7’s reported voltages to the others, if the difference remains constant, the LTC chip on CMU1 is probably faulty.

The traditional way to fix this problem is to take out and open up the HV pack and replace CMU1 (or just the chip on it) however there is an alternative:

https://myimiev.com/threads/cmu-can-‘spoofing’.5505/

Mickey

I took a trip for some errands today and got some shots at different SoCs. It looks like the difference between the regular and outlying voltages aren't perfectly linear, but I don't know if there would be any leniency there.
I did some reading in the linked thread, and the thread linked within it, and am wondering you mean to say that a potential fix for this being a CMU fault would involve using an Arduino (or equivalent) to hardware spoof the data. If that's the case, I do happen to have one handy. I do admit I'm still a little brain-scrambled after going through the discourse in those threads, and have a lot more to learn in order to keep up with all of the aspects that were brought up.
I am grateful that you reached out with so much insight, Mickey!

 

[MickeyS70]

I took a trip for some errands today and got some shots at different SoCs. It looks like the difference between the regular and outlying voltages aren't perfectly linear, but I don't know if there would be any leniency there.

The various screenshots don’t show much of a voltage difference in general, therefore maybe try to get the good ones down to around 3.7V and check on the outlier but so far it looks promising for a CMU fault.

…would involve using an Arduino (or equivalent) to hardware spoof the data. If that's the case, I do happen to have one handy.

Yes, in a nutshell the Arduino is intercepting all CAN communication from the CMUs, identifying and correcting the ‘bad’ cell data and then re-transmitting the information to the BMU.

I do admit I'm still a little brain-scrambled after going through the discourse in those threads, and have a lot more to learn in order to keep up with all of the aspects that were brought up.

It sounds a lot more complicated than it is…