3pete
Posts: 142
Joined: Tue Mar 19, 2019 9:03 pm

I took my 2014 i3 in for a battery capacity check and BMW added capacity to my battery

Tue Jul 13, 2021 4:25 pm

There are other stories like this but I figured I'd document my experience here.

All my tracking data on my car suggested my HV Traction Battery was below 70% capacity, including: Batt Kapa max hovering at 13.0 kWh and the Electrified app showing 67% SOH. The GOM indicated a range at full charge to be in the 45-55 mile range. Link to tracking data here:viewtopic.php?f=11&t=17163&p=68608#p68608


I took it to the local dealer and asked for them to check the battery capacity. They said there'd be a $130 diagnostic fee, which I pushed back on because it didn't sound like a capacity check and because @tezarc helpfully shared their story and invoice here:
viewtopic.php?f=10&t=17400&p=68984#p68984

While discussing with the advisor, it became clear that they were not aware of the 8yr warranty on the HV battery and once they found evidence of it, they found BMW's guidelines on performing a capacity check. They were kind enough that they offered to waive the fee for the test due to the confusion.

Two and a half business days later, I heard that my car passed with a 73% (a solid C-)!

When I picked the car up, I found some changes. They had to upgrade the car's software to perform the test and sure enough, my GOM range, Batt Kappa Max and Electrified app values changed. Also, some of my "coded" values in the car reverted to stock.


Batt. Kapa Max:
Before: 13.0 kWh
After: 15.4 kWh... Based on one data point.

Vehicle Software (i-step):
Before: I001-17-11-543
After: I001-21-03-530

Electrified app results:
Capacity
Before: 40.8Ah
After: 48.2Ah

SOH %:
Before: 67%
After: 80%

SOC HV % Upper Bound:
Before: 65.9%
After: 77.9%

SOC HV % Lower bound stayed at 8%


Overall, I am pleased with the extra capacity. I am especially pleased that they discounted the $400 labor charge to zero. I will keep tracking my capacity data and report back as things progress. I'm not sure whether to hope that it drops from here or stays consistent.

Obioban
Posts: 100
Joined: Wed May 22, 2019 6:16 am

Re: I took my 2014 i3 in for a battery capacity check and BMW added capacity to my battery

Tue Jul 20, 2021 6:07 am

So the software update increases how much you can charge your battery, from 66% to 80%? I don't think I've seen that laid out before.

alohart
Posts: 2425
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: I took my 2014 i3 in for a battery capacity check and BMW added capacity to my battery

Tue Jul 20, 2021 10:47 am

Obioban wrote:
Tue Jul 20, 2021 6:07 am
So the software update increases how much you can charge your battery, from 66% to 80%? I don't think I've seen that laid out before.
If so, earlier versions of the BMS might be buggy or too conservative. Another possibility is that the software update re-initialized the BMS data back to its default values such that the range will return to the earlier lower values after some driving. Hopefully, 3pete will keep us updated.

A more cynical view is that BMW knows that updating the software will at least temporarily increase the usable capacity which would help it avoid a warranty claim against the battery pack.
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

3pete
Posts: 142
Joined: Tue Mar 19, 2019 9:03 pm

Re: I took my 2014 i3 in for a battery capacity check and BMW added capacity to my battery

Thu Jul 29, 2021 12:28 pm

Obioban wrote:
Tue Jul 20, 2021 6:07 am
So the software update increases how much you can charge your battery, from 66% to 80%? I don't think I've seen that laid out before.
Yes, according to the way I'm reading the Electrified app. (Small numbers on the SOC HV% section)
Before:
Image
After:
Image


I did just get a look at my car in the mi3 app for iOS noticed it has a metric called "Cell Res. Factor" and "Cell Aging Factor" which the Electrified app does not have. It would have been interesting to know whether that also changed with my car's trip to the dealer.

alohart wrote:
Tue Jul 20, 2021 10:47 am
If so, earlier versions of the BMS might be buggy or too conservative.
It seems very likely that this is the case. Tesla has added (and removed!) range to their cars via software updates, and Jaguar added range as well with the iPace. BMW (and Porsche) tend to be conservative in their published performance specs in general so I could definitely see this translating to a conservative take on BMS.

However... If the BMS is restricting capacity below 70% within the warranty period, it should be fixed for free! I was a bit lucky in that regard but I think owners with evidence that their capacity is below 70% should not have to pay for a diagnosis or software upgrade.

3pete
Posts: 142
Joined: Tue Mar 19, 2019 9:03 pm

Re: I took my 2014 i3 in for a battery capacity check and BMW added capacity to my battery

Thu Jul 29, 2021 12:42 pm

alohart wrote:
Tue Jul 20, 2021 10:47 am
A more cynical view is that BMW knows that updating the software will at least temporarily increase the usable capacity which would help it avoid a warranty claim against the battery pack.
The tin-foil hat enthusiast in me couldn't help but notice my capacity increased to exactly 80% after the change, which seems just slightly suspicious that it's such a nice, round number! :lol:

I actually do think that part is coincidental, but the part I can't reconcile is the 73% capacity result that the dealer said the test gave. Electrified went from saying 67% to 80% and I can't come up with a formula for capacity from any of the other numbers in the app that gives me 73%. 73 Seems approximately right for the trend line in my #4) Trip kWh / Remaining SOC chart from my tracking data though.

alohart
Posts: 2425
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: I took my 2014 i3 in for a battery capacity check and BMW added capacity to my battery

Thu Jul 29, 2021 3:25 pm

Please let us know how your usable capacity changes during the next few months. If it drops back down to near what it was, that would be evidence that BMW has rigged the capacity test to minimize its liability to replace degraded packs.
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

2020i3
Posts: 35
Joined: Mon May 17, 2021 10:00 am

Re: I took my 2014 i3 in for a battery capacity check and BMW added capacity to my battery

Fri Jul 30, 2021 7:42 pm

Probably going to stick my foot in my mouth on this post, but this is my guess about how this battery degradation thing is working.

Say a car manufacturer sells you a EV with an advertised range of 150 miles and a 8-year battery warranty. The automaker knows in advance that there's yearly deterioration of the battery.

Says so here: "As you might expect, the older a vehicle is, the more likely its battery has deteriorated. However, when looking at average decline across all vehicles, the loss is arguably minor, at 2.3% per year. This means that if you purchase an EV today with a 150 mile range, losing about 17 miles of accessible range after five years is unlikely to impact your day-to-day needs."

https://www.geotab.com/blog/ev-battery-health/

So the automaker knows that after five years you can only go 133 miles in the car on a charge. They also know they're on the hook for eight years of warranty and wouldn't want buyers bad-mouthing their brand because of deterioration causing less travel range.

The smart thing to do would be to partition the battery like a SSD hard drive with software where you start with overcapacity and then have enough capacity left to get them safely to eight years despite the annual degradation. Which is going to be affected by a number of factors such as extreme hot or cold climates etc., like the article points out.

That's my thoughts on how this battery life game is being played.

The article is a good read if you've never seen it.

gt1
Posts: 384
Joined: Sat Nov 07, 2015 7:31 pm
Location: Baltimore

Re: I took my 2014 i3 in for a battery capacity check and BMW added capacity to my battery

Wed Aug 04, 2021 7:37 am

Trying my new shiny tinfoil hat...
If the car approaches the end of the battery capacity, they could remove the top and/or bottom safety limits, giving the car a range boost. It will cause the battery to degrade even faster, but why would they care if all they need for it is to last another year until it will be out of the warranty. It can be checked by monitoring the cell voltages at 0% and 100% indicated charge. Are there tools user friendlier than ISTA to do it?

alohart
Posts: 2425
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: I took my 2014 i3 in for a battery capacity check and BMW added capacity to my battery

Wed Aug 04, 2021 11:16 am

gt1 wrote:
Wed Aug 04, 2021 7:37 am
Trying my new shiny tinfoil hat...
If the car approaches the end of the battery capacity, they could remove the top and/or bottom safety limits, giving the car a range boost. It will cause the battery to degrade even faster, but why would they care if all they need for it is to last another year until it will be out of the warranty. It can be checked by monitoring the cell voltages at 0% and 100% indicated charge. Are there tools user friendlier than ISTA to do it?
Hope your tinfoil hat looks as good as mine :D

I and my tinfoil hat don't doubt that BMW is futzing with the BMS to minimize their battery capacity loss liability.

The Android Electrified app and the iOS mi3 app will show similar battery pack data as ISTA.
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

3pete
Posts: 142
Joined: Tue Mar 19, 2019 9:03 pm

Re: I took my 2014 i3 in for a battery capacity check and BMW added capacity to my battery

Wed Aug 18, 2021 4:00 pm

My understanding is that letting a lithium ion battery get to "true zero" means it is likely to never hold a charge again and charging it to a "true 100%" (especially an aged battery) has a substantial risk that it will catch on fire.

Maybe this gives BMW too much credit, but I would assume they don't want either of those things happening even if it's the day after the warranty period ends. Although they aren't liable for the battery at that point, it could tarnish their brand image.

So, with that in mind, and assuming that we already agree the BMS is programmed to "stash" capacity away from the user over time to account for degradation, I'm guessing that when they programmed the BMS they made some assumptions around battery wear and over the past 8ish years they've learned some things. Maybe they programmed the BMS to stash away a buffer of X% of battery capacity for every DC Fast Charge the car does, or Y% for every 1,000 miles driven.

From examining real-world i3 batteries since the introduction BMW could have realized their rating of X% really only needs to X/2% per DCFC. Or maybe Y% for 1,000 miles is close but they think Y% for every 1,200 miles is realistic.

They may have also thought every year of age should take off Z% only to find that it really doesn't factor in enough to matter.

Essentially if this was the case, they could update the BMS parameters and "give back" battery capacity that the BMS stashed away without risking the integrity of the battery.

Again, maybe I'm giving them too much credit, but this seems plausible to me. I will keep tracking my car's info and update you as time goes on.

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