2015 i3 Battery Degradation (20% after 30k miles)

[alohart]

The original usable capacity of the i3 battery as stated from BMW is 18.8 kWh of the actual 22 kWh. This indicates that there is 1.2kWh (5.45%) of SOC that is reserved by the BMS.

You might have meant to write 21.6 kWh - 18.8 kWh = 2.8 kWh, or ~13% of the total capacity reserved by the BMS.

Some of that is for anti bricking on the low end which would mean that "fully charged" is to your point not 100% SOC but closer to 95%.

Agreed.

 

[sogorman]

Just a quick update, my Max Kappa reading is now down to 14.7kWh.

On a side note does anyone know of someone who has had their battery replaced with BMW?

 

[EVMan]

The one think i am noticed , the rate of deterioration after 2 years and 20K miles seams to be accelerating for me

I have 2 , and weather is relatively stable , but the older car shows month by month reduction.
First 1.3 years , i did not see any significant reduction.

 

[Oleksiy]

@sogorman, @EVMan, do you track the temperature of the pack as you take readings of Batt.Kapa? It's interesting whether the TMS is that efficient as it's claimed to be.

The max I saw was 86F, but the highest ambient temperature recorded was 88F, we had a moderate summer this year. I wonder how the pack behaves under more extreme conditions of, say, Phoenix.

 

[Oleksiy]

People on German forum discuss some pack re-initializing procedure conducted by local BMW repair shops. They claim that after this procedure Batt.Kapa goes up 1-2 kWh with corresponding increase in available range.
https://www.goingelectric.de/forum/bmw-i3-allgemeines/faq-wissensammlung-fuer-den-i3-t21457.html

 

[rtanov]

@sogorman, why don't you take it to the dealer and claim the excessive degradation warranty. They have a financial incentive to do the replacement and charge BMW for it if it is excessive and BMW agrees. I don't see any disadvantage in doing so. Worst case they will reject your claim but you would have their official measurement of where the battery stands right now.

 

[EVMan]

@sogorman, why don't you take it to the dealer and claim the excessive degradation warranty. They have a financial incentive to do the replacement and charge BMW for it if it is excessive and BMW agrees. I don't see any disadvantage in doing so. Worst case they will reject your claim but you would have their official measurement of where the battery stands right now.

I guess you need to hit 30% , to get warranty

 

[EVMan]

People on German forum discuss some pack re-initializing procedure conducted by local BMW repair shops. They claim that after this procedure Batt.Kapa goes up 1-2 kWh with corresponding increase in available range.
https://www.goingelectric.de/forum/bmw-i3-allgemeines/faq-wissensammlung-fuer-den-i3-t21457.html

While the pack re-initializing will have an immediate effect on readings, sooner or later it will catch up on the actual status of the battery.
Cycle complete battery from full to 0 , will also kind of re-initialize.

 

[EVMan]

@sogorman, @EVMan, do you track the temperature of the pack as you take readings of Batt.Kapa? It's interesting whether the TMS is that efficient as it's claimed to be.

The max I saw was 86F, but the highest ambient temperature recorded was 88F, we had a moderate summer this year. I wonder how the pack behaves under more extreme conditions of, say, Phoenix.

How do you take this temperature reading of the pack ?
Higher the temp, the battery capacity increases, but will effect life negatively.
88 looks reasonable.

 

[rtanov]

@sogorman, why don't you take it to the dealer and claim the excessive degradation warranty. They have a financial incentive to do the replacement and charge BMW for it if it is excessive and BMW agrees. I don't see any disadvantage in doing so. Worst case they will reject your claim but you would have their official measurement of where the battery stands right now.

I guess you need to hit 30% , to get warranty

The last measurement in the OP's doc shows >30% degradation - the 3 measurements there vary significantly, so it depends on how the dealer measures it. Also, even if not quite 30% but close they might be willing to work with him to get the warranty approval by BMW as they will make money on the replacement work. If I were in OP's position I'd go for it - it would give me one extra data point on the battery degradation state and help plan how to proceed in maintaining or stressing the battery in the future.

 

[Oleksiy]

How do you take this temperature reading of the pack ?

It's in the hidden menu, "14.05 Batterietemp" subitem.

I believe my pack's 86F is ok, but we've had quite low summer ambient temperature this year. Just wondering how the battery behaves under 110F Arizona weather.

 

[Oleksiy]

While the pack re-initializing will have an immediate effect on readings, sooner or later it will catch up on the actual status of the battery.
Cycle complete battery from full to 0 , will also kind of re-initialize.

Did you try to complete such a cycle? Any success in increasing Batt.Kapa?

I'm not sure the BMS reports the actual satus of the battery correctly. So once my pack's capacity goes down to 16 kWh according to the car's self-reporting, I'd be happy to have the battery reinitialized so that I have 17+ again, corresponding to the real capacity at the moment other than relying on some guestimate by BMS.

This is what happened to 30 kWh Leaf. Recently Nissan has circulated a firmware upgrade, and people saw their capacity increased by 1-2 kWh with the corresponding increase in range. Eventually, this added capacity will fade away as well. Only now it will fade from 17+ to 16 kWh rather than from 16 to 15 (based on i3 numbers).

 

[alohart]

I believe my pack's 86F is ok, but we've had quite low summer ambient temperature this year. Just wondering how the battery behaves under 110F Arizona weather.

Several hot climate i3 drivers have reported lost power bars/limited power after their i3's had been parked in the sun over hot asphalt on a 110+º F day similar to what happens when an i3 battery pack's temperature is very low in cold weather. It would be interesting to know what the battery pack temperature must be for its output power to be artificially reduced.

 

[alohart]

I'm not sure the BMS reports the actual satus of the battery correctly. So once my pack's capacity goes down to 16 kWh according to the car's self-reporting, I'd be happy to have the battery reinitialized so that I have 17+ again, corresponding to the real capacity at the moment other than relying on some guestimate by BMS.

Because the displayed charge level percentage is a calculated rather than a directly measured value, it can be inaccurate. Maybe reinitializing is recalibrating the displayed charge level percentage so that it is more accurate. If so, reinitializing could result in a gain or loss in usable battery pack capacity. An inaccurate displayed charge level percentage could result in an inaccurate Batt. Kapa. max value assuming that its algorithm extrapolates the energy added during charging over a partial inaccurate charge level range to the full 0% to 100% charge level range.

Or maybe reinitializing is cell charge level balancing that dealers can do with specialized equipment much more rapidly than an i3's built-in balancing. That would increase the usable battery pack capacity if significant cell charge level imbalance existed.

 

[EVMan]

How do you take this temperature reading of the pack ?

It's in the hidden menu, "14.05 Batterietemp" subitem.

I believe my pack's 86F is ok, but we've had quite low summer ambient temperature this year. Just wondering how the battery behaves under 110F Arizona weather.

So , i have observed , when i start i3 in morning, sometimes the battery cooling AC turns on , and some times not.
While it is likely to happen , when its hot , it kind of happens randomly , even on cold days.

If any one observed , any patterns for, the battery cooling AC turning on with the battery temperature , do comment.
I have not observed any pattern with the California weather , except for , when its really cold.

 

[Swede1]

I suspekt my battery tok damadge from heat this summer. Batt kapa max 17,2 , after emptying and recharge to 100 %, it raised to 18,2 kWh temporarly, now its between 17,2 and 17,9. Before, maybe a year ago i think it was over 18 possibly somtimes over 19 kWh. I recognised fast ac charging was quicker, 7,4 kW , down to 45 seconds per 0,5 percent battery increase. Thought it was a good charger, but now i guess the battery has degradering a little. Before it was around 1 minute for Evert 0,5 % increase in charge level.

 

[brin]

Hello, I believe, there was a bug introduced into firmware in some 1 or 2 year old firmware. My i3 BEV 2014 was pretty ok till last summer (1,5 year ago). It still had 19,5 readings of Max Kappa. Since then, capacity started deteoriating rapidly. And when I say rapidly, then I mean that after that winter year ago, it went from 19,5 kWhs to 17,5 kWhs. I checked it irregularly and this year from spring to today it went again down from 17,5 to 16,9. So not such a hit again, but a fast loss compared to what I experienced first 2,5 years. My friend from Turkey actually did the reinitialisation himself (you need ISTA installed) and his real usable capacity went from 16,5 kWhs he experienced longterm to 19,3 kWhs. Since then it deteoriated slightly after half a year to 18,5 kWhs, but that is still pretty much ok for a 2015 BEV. I am waiting for my OBD2 adapter and after that I plan to do this procedure myself and I will let you all know, what results I got. This fast deteoriation looks pretty much like a bug, I live in mild climate and I charge slowly if possible, only occasional DC use.

 

[TheMK]

Do you know how to do the battery capacity re-initialization through ISTA? I know in the "service" menu where you can enable roller mode, and check the battery capacity, there's an "Int. BC/Range" option. Does BC refer to battery capacity?

 

[brin]

That init. option in ISTA should be under battery tab. It supposedly was made due to those calibration problems, which left a few cars stranded.

 

[rockphone]

Battery warranty is 8 YEARS and 100K miles from the initial service date when car was actually sold. Therefore if you get down to 13.2kW in the secret BC menu you should demand battery replacement.