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Acceptable cell imbalance range?

Alset2

Member
Supporting Member
Feb 20, 2020
120
39
Ocala. Fl
M3.jpg
MS.jpg
Here I am attaching screenshots of SMT for both my wife's M3 and my MS (both 2020) .

Just wondering if this is normal or should I do a charge to 95% ? I think thats the way to get cells to balance, but please correct me if I'm wrong.
Actually, form all my reading it really appears that M3 is 90% and MS is 93% to initiate balancing, so I just figure ill do both at 95% to be sure. However any input is welcome, I love learning more about these cars !

Thanks
 

Alset2

Member
Supporting Member
Feb 20, 2020
120
39
Ocala. Fl
Thank you for the response.
The MS was around 60% SOC (its the lower imbalance #) . I have only checked it twice with SMT and it was about the same both times.

But my wifes M3 seems to have gone up 4mvs in 2 months (it was 2mv back in May). I was hoping there were some hard #s known like up to 6mv is ok, anything over needs balancing...something like that ...

Wifes M3 was at 90% at this scan . Should these scans be done closer to 100% or is that not that important?

Thanks again
 

emir-t

Member
Oct 28, 2013
452
554
Istanbul
They're balanced the most when;

a) They're on higher SoC
b) They have no load on them, potentially even when contactors are open. Even AC's 2-3kW of load would create a minor imbalance momentarily.

Overall you don't have to worry at all about Tesla's pack management as far as cell voltage balances are concerned. They are industry leaders by far on that. What you might need to worry about is advertised battery capacity vs real capacity. That was an issue when they were naming models with capacity (75-85-90) They got away with that now that they're only advertising an obscure 'long range'. Since you've got the new age Teslas (both M3 and MS you have are new) you don't have anything to worry about.
 

Alset2

Member
Supporting Member
Feb 20, 2020
120
39
Ocala. Fl
They're balanced the most when;

a) They're on higher SoC
b) They have no load on them, potentially even when contactors are open. Even AC's 2-3kW of load would create a minor imbalance momentarily.

Overall you don't have to worry at all about Tesla's pack management as far as cell voltage balances are concerned. They are industry leaders by far on that. What you might need to worry about is advertised battery capacity vs real capacity. That was an issue when they were naming models with capacity (75-85-90) They got away with that now that they're only advertising an obscure 'long range'. Since you've got the new age Teslas (both M3 and MS you have are new) you don't have anything to worry about.

Thank you for taking time to respond.
My mind goes crazy with the data available with SMT...lol

Honestly though, I am very interested in it all, but I am also pretty good with understanding the reality "is what it is" with these batteries.
It also seems that these readings are somewhat dynamic to a certain degree. I'm thinking they can vary up to a % or 2 simply based on the "time of day" the test was run.

Still all very interesting to me .
Once upon a time , long long ago, I was an ASE certified master tech that specialized in Asian sports cars (with lots of SCCA club and pro racing ) , so for me this is an all new frontier to learn about .

I spend WAY too much time on forums reading about these cars.
I guess I'm all in !! lol
 

beatle

Active Member
Aug 31, 2019
1,277
757
Springfield, VA
In general it would be better to just relax and drive, but Tesla has done some underhanded things with the batteries that warrant a closer eye. In the end, the battery is what the battery is, and for the most part you should be fine if you don't obsess about things like supercharging speed and tenths of a second 0-60.

Of course my statement will likely draw the ire of people who are incredibly upset about the speed at which their car charges or discharges, but in general these nerfs are not enough to drive people away from owning the car, so the anger does no good.

FWIW, my car's cell imbalance is also 3.97mv. This is at 73% SoC
 
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Reactions: aerodyne

Alset2

Member
Supporting Member
Feb 20, 2020
120
39
Ocala. Fl
In general it would be better to just relax and drive, but Tesla has done some underhanded things with the batteries that warrant a closer eye. In the end, the battery is what the battery is, and for the most part you should be fine if you don't obsess about things like supercharging speed and tenths of a second 0-60.

Of course my statement will likely draw the ire of people who are incredibly upset about the speed at which their car charges or discharges, but in general these nerfs are not enough to drive people away from owning the car, so the anger does no good.

FWIW, my car's cell imbalance is also 3.97mv. This is at 73% SoC


Thanks.
I understand the risk of posting and I really can see both sides of it . But at the end of the day, at least today, I cant do anything about what battery I have. Believe me , I want all the battery I can get but I do not let my curiosity detract from the absolute joy of driving this car ...I just like knowing what is going on with my car.

Its more my wifes that has my attention.
She does do a lot of partial charges at work because we are waiting on the install of her wall connector (gen3) , so now she can only charge using 110 volts.
Once or twice a week she charges a full charge (usually 80%) at home on our WC to top it off.
Ironic enough , here battery degradation seems to be way less than mine..lol

Anyway, thanks again for responding .
 

aerodyne

Nose cone car - to be replaced 3-10 / 4-07?
Nov 19, 2018
3,716
6,036
Los Angeles
I have 10 times the imbalance you guys are reporting, unless I charge to 70% and drive. The lowest I have seen since March when I got SMT is 14mv.

Module 2, string 1 seems to be the problem child for me.

Not noticing any problems except my range drops about 6 miles when stored. It comes back up to 265 when charged and driven
 

aerodyne

Nose cone car - to be replaced 3-10 / 4-07?
Nov 19, 2018
3,716
6,036
Los Angeles
View attachment 561041 View attachment 561042 Here I am attaching screenshots of SMT for both my wife's M3 and my MS (both 2020) .

Just wondering if this is normal or should I do a charge to 95% ? I think thats the way to get cells to balance, but please correct me if I'm wrong.
Actually, form all my reading it really appears that M3 is 90% and MS is 93% to initiate balancing, so I just figure ill do both at 95% to be sure. However any input is welcome, I love learning more about these cars !

Thanks

I noted you have obvious errors on the SMT range values. Try unchecking "Release 2020 or higher" under the wrench icon toolbar.

In my experience, I get fully callibrated, even after months of storage, going to 80%.
 
I have 10 times the imbalance you guys are reporting, unless I charge to 70% and drive. The lowest I have seen since March when I got SMT is 14mv.

Module 2, string 1 seems to be the problem child for me.

Not noticing any problems except my range drops about 6 miles when stored. It comes back up to 265 when charged and driven


The best way is too make a drive and use the AP and them check the unbalanced. my model 85 S 2015 have a unbalances of 20/30mV. And in idle states while charging it is 5mV.
 

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