Anyone keeping track of the battery's soh
- Thread starter Luis Abreu
- Start date
- Replies 146
- Views 26K
-
- Tags
- battery degradation
MrSnrub
Well-Known Member
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
Outagas
Member
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.
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.
Last edited:
pictsidhe
Well-Known Member
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.
Outagas
Member
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
Outagas
Member
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…
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…
MrSnrub
Well-Known Member
I just don’t bother. Can’t have a headache if you know what triggers itLol - too late
Being that guy has saved me a butt-load of dollars over the years.
I’ll bring you some aspirin next time
fizzit
Active Member
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?
Luis Abreu
Member
Hello guys,
After 61400 km, here's the state of the battery of my mini:
I'm rather pleased with this, specially because in the last 2 years most of my charging has been done through 50kw DC chargers (and with 41k, BMS whas alreayd saying that SOH was aounr 95%).
After 61400 km, here's the state of the battery of my mini:
I'm rather pleased with this, specially because in the last 2 years most of my charging has been done through 50kw DC chargers (and with 41k, BMS whas alreayd saying that SOH was aounr 95%).
Luis Abreu
Member
Sorry.
Don't know what happened...can you see it form this link?
https://photos.app.goo.gl/HU2T2vSFvD43oeum9
and I've noticed something: how can the battery capacity be higher than what the specs say (if I'm not mistaken, it should be 32.6kwh total, but my current value is higher)
Last edited:
teslarati97
Well-Known Member
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!
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!
Luis Abreu
Member
Hello guys.
It's weird, no doubt...however, if you go through this thread, there are other guys which have similar data. For instance, @Darrell Hayes mentions his total capacity in a previous post. I've talked to some local guys that have recorded somethign similar to the data shown on this thread (btw, I assumed 380V presented by the app is correct, but that might not me the case...)
It's weird, no doubt...however, if you go through this thread, there are other guys which have similar data. For instance, @Darrell Hayes mentions his total capacity in a previous post. I've talked to some local guys that have recorded somethign similar to the data shown on this thread (btw, I assumed 380V presented by the app is correct, but that might not me the case...)
fizzit
Active Member
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… 
Luis Abreu
Member
Hello again.
Even using the official volts as per spec (350V instead of 380), it simply doesn't add up...
Even using the official volts as per spec (350V instead of 380), it simply doesn't add up...
fizzit
Active Member
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