Anyone keeping track of the battery's soh

So as far as I can tell, the SOH % that we see in Electrified and mi3 is a magic number. We don’t know how it’s calculated, how it relates to the car’s performance or driveability, and whether or not Mini/BMW uses it as a diagnostic indicator for when to repair the battery.

 

No offence but being in the business I try to keep things minimal especially to people who have no tech knowledge. Helps avoid endless questions, then client going home and coming on here then calling or stopping by asking endless questions. Basically making up problems that don’t exist. So a dealer printing out state of heath is completely useless because what are most people going to interpret from it?

It’s similar to printing out a DME ECU log from a Porsche let’s say. You have x hours and over rev at xxx. Then you have to explain for 30 mins that it happened early in the cars life, what the over rev level is etc. Then they’ll go ask on rennlist then call me back asking the same

the general public doesn’t want warning lights or noises

 

Exception would be pre purchase inspection

 

No offence taken - cars are a big expense. I’d take a customer’s interest as normal. For me, I generally end up knowing more about the products I buy and use than the vendor. No where has this been more true than automotive. You think your conversations are frustrating - lol. I once spent 30 minutes trying to convince a service advisor that if he would only ok replacing the rear clutch pack input bearing of my ICE AWD system he wouldn’t need to toss the entire unit and charge me $3500 while doing it just because it was noisy. Nope - was like talking to someone who hadn’t a clue - or was well trained to give educated customers the brush off because 90% of his dealer walk-ins probably shut up and pay up and that’s where the money is. So did it myself at home with $200 in parts right out of the SKF catalogue and a cheap-o hydraulic press.)

My motto is give me ALL the data and I’ll decide what’s important. And where there’s a learning curve such as with an EV that’s new to me, the tech that’s going to spend some extra time with me is someone to respect.

 

Yes all the data so you can do what with it ? Put it into a spreadsheet and give yourself a headache? Then spend 30 mins giving the guy at the dealer a headache ? Don’t be that guy…

 

The SOH is calculated by the BMS. A BMS usually calculates battery capacity from voltage and coulombs. The BMS should also have data on individual cells, which we do not currently have access to.
My car is currently spending a little over a week on level 1 charge at an airport. I really should have read the SOH before plugging it in.

 

Lol - too late
Being that guy has saved me a butt-load of dollars over the years.
I’ll bring you some aspirin next time

 

Downloaded that Mi3 app some folks have recommended.
It’s my first time with a Bluetooth OBD module however. All my other analyzers are dedicated plug in units.
The image below is all I get - looks like evidence of data transfer as that counter climbs but no results.
Can anyone tell me what I may be doing wrong?
Have tried Off, On, Ready to Drive states…

 

I just don’t bother. Can’t have a headache if you know what triggers it

 

I know that the SOH is probably calculated by the BMS. But a BMS has many inputs and we don’t know how it derives the SOH, as far as I can tell. A percentage on its own is a unitless number with no real-world meaning. Is it based on estimated capacity divided by nominal capacity? Internal resistance? Variance of cell internal resistance or capacity? Cell voltage variance? Number of pack cycles?

 

1year old, 13,320 miles.
I hope the degradation slows down, or speeds up enough for a warranty battery.
:-D

'Electrified' app for Android.

 

Não consigo ver a foto, Luis.

 

34.92 kWh? Yeah something is amiss.

 

The battery capacity will fluctuate with voltage x amp hours.

For example the nominal cell voltage of the BMW i3 (2017-2019) Samsung SDI 94Ah is 3.68V. There are 96 cells in series so that is 353.28V nominal * 94Ah = 33.2kWh. If all cells are at 3.96V then you would get 96 x 3.96V x 91.9Ah = 34.9kWh. I'm not sure on the exact specifications for the CATL battery on the SE.

Measuring state of health is very tricky because there are various indirect methods of measurement and no set standard from what I know of. If you still manage to get decent range with very frequent DC fast charging, then the CATL batteries and BMS have done a good job!

 

That’s interesting that everyone here is seeing over the nominal capacity, which I assume is 33kWh/(96 cells * 3.7v) = 93Ah, which lines up with the old i3 pack capacity. Mine was showing over 100Ah a couple years ago, now it’s at like 97Ah. If these numbers are correct, that seems like a good sign for our battery longevity. Now if there were a way to increase the high voltage cutoff a bit for road trips…

 

Do you mean the mismatch between the nominal capacity and the capacity we’re seeing in electrified/mi3? I agree, it’s strange. I have 2 theories:

1. The raw data from the car isn’t the floating point amp hour value. The app has to multiply it by a constant to get the displayed capacity, and this constant is valid for the i3 but not for the SE.
2. MINI/BMW asked CATL for a battery that would provide 93Ah at 0ºC. They couldn’t make a cell that magically holds its nominal capacity down to below freezing, so they made one with a little extra capacity that meets the nominal spec at freezing. If this is true then we’d expect to see the Ah be close to nominal for people who only drive in freezing climates