Greetings from the other side of a HV battery warranty replacement.

[tezarc]

I own a 2014 BEV and had been keeping a log of the battery kappa max after noticing marked range decrease. Before I started logging I brought the car to the dealership with the concern and was told there was nothing wrong, not having any idea what tests are even performed for that result. The GOM would decrease fairly rapidly even while standing still once the battery reached around 40% yet the kappa max reading never went below 15.0kWh, which is above the 70% capacity mark where the warranty triggers. Skip 1.5 years to this spring and the car is getting only 50-55mi actual range (GOM would always indicate at least 65mi) on a full charge. Kappa is still 15.0kWh.

Not sure whether my battery warranty is 8 or 10 years (this is the 8th year) I took the gamble and had the dealership perform the battery warranty test. I had to specifically ask for a "battery test for warranty purposes" to get to that point. I was told that the test takes 2.5 hours worth of labor and should the batteries pass I would be on the hook for $600(!). I suppose this is BMW's way of dissuading owners from filing warranty claims. I nervously signed the estimate.

Two days later I received a call from the service rep to tell me that the batteries failed (whew!) and that the replacement batteries would be coming in from Germany and take approximately 3-4 weeks to arrive. The test returns only a pass or fail (what is this, grade school?). When I took back the car to await the arrival of the replacement battery it seemed that the techs had upgraded the Body Domain controller firmware to do the test because all the coding changes I had made to that module was reset and the battery icon next to the GOM had changed. Coding changes to the other modules were intact however. Also the GOM shows correctly that 55mi is the most I could travel on a full charge. This observation along with others account of seeing their range go up after requesting the same test seems to mean part of the test is making the BMS re-learn the battery.

Fast forward 3 weeks and the batteries had arrived. Took the car back to the shop and 4 days over the weekend I get my i3 back with a battery capacity like when it came off boat from Leipzig.

TL;DR:
I gambled against a $600 labor charge that my 2014 BEV i3's HV battery is below 70% capacity despite the kappa max reads 15.0kWh and fortunately won.

Do not depend solely on the kappa max reading to measure your battery capacity.

Drive a significant distance without turning off the motor and record distance traveled, charge levels at start and end, and measured consumption rate of that drive using eDrive. Then use the formula "distance_traveled÷consumption_rate÷(charge@start-charge@end)÷nominal_capacity" to get you a better approximation to decide whether to ask for the warranty test or not.

For those interested, link below to the work order with service codes performed during the battery replacement.
https://imgur.com/a/ja5vYuQ

EDIT: fixed typo iDrive→eDrive, clarified equation and added one more observed detail after taking car back before battery replacement.

 

[alohart]

Drive a significant distance without turning off the motor and record distance traveled, charge levels at start and end, and measured efficiency of that drive using iDrive. Then use the formula "distance_traveled÷efficiency÷(charge@start-charge@end)÷nominal_capacity" to get you a better approximation to decide whether to ask for the warranty test or not.

When you did this calculation, what was the result that convinced you to have the capacity test performed?

 

[tezarc]

This is the last line of my log:
44mi÷3.8mi/kWh÷(1.0-0.03)÷18.1KWh=.6595 or 65.95%

Close to the 70% I know but at that point I couldn't take the car to go anywhere without having to go limping home on ECO Pro+ like a turtle with the AC off in the summer or stop at a L2 charger again with the AC off because the heat pump is being used to cool the battery while charging. Tolerated that for 2 summers and don't want to do a 3rd. Thus the gamble.

 

[alohart]

44mi÷3.8mi/kWh÷(1.0-0.03)÷18.1KWh=.6595 or 65.95%

The nominal capacity is generally considered to be 18.8 kWh which would result in an even more compelling reason to pay for a capacity check: 63.49%. Anything below 65% would probably convince me to pay for the capacity check. Unfortunately, the capacity of our battery pack is ~77% of the nominal new usable capacity and is unlike to drop below 65% by November, 2022.

Congratulations on your new battery pack! Here's hoping that it will perform much better over time.

 

[i3Houston]

44mi÷3.8mi/kWh÷(1.0-0.03)÷18.1KWh=.6595 or 65.95%

The nominal capacity is generally considered to be 18.8 kWh which would result in an even more compelling reason to pay for a capacity check: 63.49%. Anything below 65% would probably convince me to pay for the capacity check. Unfortunately, the capacity of our battery pack is ~77% of the nominal new usable capacity and is unlike to drop below 65% by November, 2022.

Congratulations on your new battery pack! Here's hoping that it will perform much better over time.

God I hope so. Is there a way to confirm the manufactory date of the pack? The new packs would certainly be more resilient but not sure if BMW would just install something from back when?

 

[alohart]

Is there a way to confirm the manufactory date of the pack? The new packs would certainly be more resilient but not sure if BMW would just install something from back when?

I'm not aware of any way to determine when individual battery pack modules or the cells that they contain were manufactured.

I am not confident that a replacement 60 Ah battery pack would be any less prone to degradation than an original pack. The cells would be the same 60 Ah Samsung SDI cells. I don't know whether 60 Ah warranty replacement modules were assembled in 2014 - 2016 or whether they were assembled more recently with new cells or with used cells sourced from other battery packs.

The cell chemistry of 94 Ah and I assume 120 Ah cells is somewhat different from that of 60 Ah cells. The newer chemistry seems to degrade much more slowly based on almost no reports of significant degradation. It's too bad that BMW doesn't offer the option of a 94 Ah battery pack when it replaces a 60 Ah pack under warranty, even with a reasonable additional cost to the owner.

 

[3pete]

Took the car back to the shop and 4 days over the weekend I get my i3 back with a battery capacity like when it came off boat from Leipzig.

Congrats, and this is great to hear that BMW really does replace battery packs, even if rare! Also it's evidence that the line of "the car will call us if the battery is out of warranty spec" is false.

Do not depend solely on the kappa max reading to measure your battery capacity.

Drive a significant distance without turning off the motor and record distance traveled, charge levels at start and end, and measured consumption rate of that drive using eDrive. Then use the formula "distance_traveled÷consumption_rate÷(charge@start-charge@end)÷nominal_capacity" to get you a better approximation to decide whether to ask for the warranty test or not.

Did you use this formula regularly in your logging, and if so, how consistently did it come out below 70%? I've been charting a lot of stuff on mine for a while and that is the only metric that still shows mine above 70% more often than not (thought it's also very close). It's chart #4 in my latest numbers here: https://www.mybmwi3.com/forum/viewtopic.php?f=11&t=17163&p=68608#p68608

I'm wondering if I have the opposite scenario of yours: where my car under-estimates range and batt kapa max until I actually use it. However, when the GOM at 100% says 53 miles, I'm not particularly inclined to set out on a 60 mile trip...

 

[tezarc]

Did you use this formula regularly in your logging, and if so, how consistently did it come out below 70%?

However, when the GOM at 100% says 53 miles, I'm not particularly inclined to set out on a 60 mile trip...

Whereas I do a kappa max reading almost daily at 100% charge except if I'm running late,
I try to do that formula test run at least every 2 weeks. Because I do a run specifically to record those numbers. I do so in the evening usually after 10pm so traffic would not be a factor, using the same route. Just run out till the battery is at 50-55%, do a U-turn and drive back home. The runs I did after the winter ended (4-5) was my decision maker. Of course that number was below 70% before the end of '20 but like you (and I suspect many other owners) I was hesitant to gamble that much money.

Looking at your numbers you have a better case than I for requesting a warranty test. Your GOM and your kappa max reading supports each other. Of course I cannot predict your outcome. It's unfortunate that you have to wager that 2.5 hour labor charge to claim it.

 

[gt1]

Congratulations on the new battery! Does anyone know how the test is conducted? I'm thinking about a charge/discharge cycle with the battery temperature conditioning. Probably possible to do at home with a power measuring EVSE.
The question of the replacement cells is interesting since they were likely manufactured before 2017.

 

[eNate]

I'd like to think they're not new old stock. Lithium Ion batteries have a shelf life of sorts -- they need to be maintained periodically. I'd imagine it's expensive to manufacture, warehouse, and maintain a battery pack with the possibility of it degrading, vs. just custom assembling one (or a small batch of them) on an as needed basis. There's got to be an accessible date code on the replacement pack somewhere where a future BMW tech could easily inspect it.

 

[3pete]

Looking at your numbers you have a better case than I for requesting a warranty test. Your GOM and your kappa max reading supports each other. Of course I cannot predict your outcome. It's unfortunate that you have to wager that 2.5 hour labor charge to claim it.

Thanks - my car was already at the dealer but this made me feel a lot better that I wasn't just wasting my time and potentially money by having them test it. Even better- the wager turned out to be for $0.

I wrote up a full report on what happened, but the short version is: the dealer added 2kWh back to my battery ...somehow... (magic!) https://www.mybmwi3.com/forum/viewtopic.php?f=10&t=17409#p69027

Also, I meant to ask: is your 'new' Batt Kapa Max around 18.8, or closer to 20?

 

[WalterH]

BMW just tested my 2014 BEV at 72% with 3 months left on the warranty, so I created another post here to get ideas on how to diminish the capacity enough for a replacement: https://www.mybmwi3.com/forum/viewtopic.php?t=17723