Not charging over 3,9 V per cell

[brin]

Hi guys. I have iMiev, where I changed cells inside the battery, as direct swap of batteries was impossible as my car is 2012 and battery donor is 2016. Internals were very close between those models and compatible, so swap was work intensive, but nothing that complicated. Older version has better battery pack in my opinion, better solved water insulation etc. None the less, I tried to use capacity measure function in HobDrive to fix it to correct capacity and it doesn't work. It always fails, as it for some weird reason stops charging at 3,90 V per cell and it should charge till 4,11 V. Is there anyone who could give me a hint, what is wrong? I tried to get my hands on a proper diagnostic for iMiev, C-Zero or Ion to do proper reset of the battery, but no luck so far.

 

[MickeyS70]

Hi guys. I have iMiev, where I changed cells inside the battery, as direct swap of batteries was impossible as my car is 2012 and battery donor is 2016.

Hello
Curious as to why a direct swap was impossible, did you run into Vin related issues?
Even if the 2016 battery chemistry is different (LEV50N vs LEV50 cells), the charge shouldn’t stop at 3.9V.

Have you observed the battery voltage of individual cells during charge? One possible explanation is that one (or more) cell(s) reach 4.1V sooner than the others, stop the process and then fall in line with the others when no current flows.

How many bars does the car/what SoC does HobDrive show when fully charged?

Mickey

 

[brin]

Batteries had different connectors and I was unable to locate pinout of the connector to change it, so... I had to do the swap. I already had the new battery in the car and then found out, it won't work. Cells are perfectly balanced from about 3,7 V and above. Differences are miniscule. So I really cant see a reason, why it stops charging at 3,9 V. It does it every time. I did diagnostics, no results, clean bill. I thought it had to do something with previous battery cells, where a few had high internal resistance (like a lot, they were dying).

 

[MickeyS70]

I thought it had to do something with previous battery cells, where a few had high internal resistance (like a lot, they were dying).

Strange indeed, are you seeing 100% SoC (16bars) when the car ‘thinks’ it’s fully charged? If not what happens if you disconnect the cable and start again?

Btw what are using to charge, AC or DC, any difference with a granny charger?

Presently the car doesn’t know that the cells were swapped and as you rightly suggested, one potential way out of this is to do a battery reset but you need dealer grade diagnostics (MUT3 or a cheap Lexia/Diagbox clone) to do this.

 

[brin]

Yes, I see full bars on GOM, and the charging is really finished. Using AC, but used even DC just to try it and it is the same.

And yes, working on getting my hands on diagbox...

 

[brin]

Chemistry is practically the same, but I agree, there is probably some safety lockout of BMS. We will see.

 

[kiev]

Brin said "Cells are perfectly balanced from about 3,7 V and above. Differences are miniscule."

What was the max and min cell voltages? How much are you calling miniscule? We would need some real voltage data for each cell out to 3 decimal place to determine what is acceptably small, e.g. 3.9 vs 3.905

 

[PV1]

Sounds like the coulomb counter needs calibrated. Has the pack been run down to 2 bars since replacing cells?

 

[brin]

Miniscule like at 3,9 V, they are all 3,900 or 3,905 on one or two. Mostly they are exactly the same.

And yes, I tried to calibrate it driving it till it died several times... Not very happy experience.

Does someone know, what are the two conditions to do battery calibration process?

 

[kiev]

1. Fuel gauge down below 2 bars.

2. Let it charge till Full (16 bars).

ps So you didn't have any single cell that was outside the 3.900 +/- .005 range? That seems very good balance

 

[brin]

Yes, balance is great. Those two conditions were met, still it did not work. Hm. Still trying to get access to diagbox.

 

[MickeyS70]

Actually 16 bars doesn’t always mean fully charged, it’s 100% SoC you should check.

See discussion below for detailed description of capacity adjustments by ODBZero

https://www.goingelectric.de/forum/viewtopic.php?t=77581&start=20

 

[Gary12345]

If the cells are a different chemistry then you should have moved the BMS from the donor car - the BMS is not inside the battery pack, it is under the back seat. If the battery pack is different then you need the BMS which goes with the pack !

 

[brin]

They are not.

 

[MickeyS70]

Gary12345 has a point, most likely your car was originally equipped with LEV50, while the 2016 pack is definitely made of LEV50Ns (physically identical but slightly different chemistry).

The theory goes that if there is a mismatch, a BMU swap could indeed be beneficial…

 

[brin]

It may be, but problem is not in BMS doing weird things.

 

[MickeyS70]

It may be, but problem is not in BMS doing weird things.

… are you sure? IMHO it looks like your original BMU cannot deal with the new pack? I read somewhere that during warranty battery replacements (LEV50s with LEV50Ns) dealers need to update the FW of the BMU…

 

[brin]

It may be, but that should be longterm issue due to different discharge curve of the cells. Thats not the current problem I am facing.