Huge MV diff on replaced modules

My Nissan Leaf Forum

Help Support My Nissan Leaf Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Elliskenny100

Member
Joined
Jan 5, 2023
Messages
6
Hi All
I have a 2019 leaf which had the Service EV system fault. long story short 2 modules were replaced. But on leafspy im getting a 161MV diff on a bank of 4 cells in the pack. Obviously the 4 they replace within those modules. Is there any way to get this down or should i get back on to Nissan about this. Im worried it will never balance itself out and will effect the packs life and range.
Thanks
 
I'm waiting to get my car back from the same repair. I had a weak cell #1

I'm guessing the voltage is higher on the newer cells? if so, I don't think that is a problem and will eventually get closer to others as the cells age.
 
If the replacement module/cells are higher than the rest of the pack, eventually it will balance out.
However, ~160 mV is huge and it may never truly "balance". For example, I did my own module replacement and (unfortunately) ended up with an ~80 mV difference which will probably take months to "balance" (I've made up ~10 mV in a few weeks).
I would expect better work from a dealer, but at least you won't have a problem at the bottom end of the pack; you just won't get a "full" charge.
 
For some reason i cant post the image from leafspy here .The module that was replace has weaker voltage then the rest of the pack so looks to me like they never balanced the cells properly
 
Elliskenny100 said:
For some reason i cant post the image from leafspy here .The module that was replace has weaker voltage then the rest of the pack so looks to me like they never balanced the cells properly
If that's true (the new module is lower than the rest of the pack), you have a problem. The new module will never "catch up".
 
Stanton said:
Elliskenny100 said:
For some reason i cant post the image from leafspy here .The module that was replace has weaker voltage then the rest of the pack so looks to me like they never balanced the cells properly
If that's true (the new module is lower than the rest of the pack), you have a problem. The new module will never "catch up".

Interesting -- I would not have guessed that to be the case. If the replacement module is itself weak your statement makes sense to me, but how about if it is simply discharged ?

I would try to discharge the pack to turtle, and then leave it charging for a day. Perhaps even repeat this cycle multiple times before I declared it a bad module.
 
yes the voltage is always lower on the new module. I got back on to Nissan tech they say to discharge then charge a few times see if it will balance. But it will never catch up the other cells. I have to call back in 2 weeks and if its still the same which it will go back to get that module re balanced correctly like they should have done in the first place. According to the manual they should charge the pack to full then take out the module and balance that to the rest of the average in the pack. I would say they balanced it when the car went in for repair it was down under 20% SOC.
Did 2 balances here but its still the same 191MV at 100% and down to 60MV when the pack is low. Will be calling back in 2 weeks. Nissan havent a clue or dont follow the procedures here in Ireland.
Awful service from them
 
The best/only way to install new modules is to "top balance" the pack; the trick is to get the new module as close to the rest of the pack as possible. To be honest, it's not that easy (even I left the replacement module a bit "high")...but trained Nissan service techs should know better. Now they are going to have un-seal/re-seal the pack since you basically have to do everything you did the first time to access/separate the individual module.
 
Back
Top