Just bought a used BMW I3

[UsedBmWI3]

So I bought a used BMW I3 120ah from 2020!

The bid deal is that already had 115k km! It was a one owner car and I had the batteries tested in BMW before I made the deal!
I was expecting a good amount of degradation and if it was bellow 95% of capacity I would not made the deal!

To my surprise it was at 100% os capacity! It’s amazing how a well treated EV car can last!

Already put more 10k km in the car and still performs and have a 250km range riding comfortably!

Just wanted to share this story to show to some undecided future EV owners that a used EV it’s not a bad ideia if you are willing to put some money on batteries testing!

Have a nice ride everyone

 

[alohart]

So I bought a used BMW I3 120ah from 2020!

Congratulations!

The bid deal is that already had 115k km! It was a one owner car and I had the batteries tested in BMW before I made the deal!

Did BMW do the comprehensive battery capacity test that they do for battery capacity warranty claims? This test involves completely discharging and then fully charging the battery pack to measure the energy vended/consumed. This can take several hours and generally costs a couple hundred dollars in the U.S. Even after this test, some U.S. BMW dealers provide just a passed/failed result without a measured capacity which varies with temperature and with how fast the battery pack is charged/discharged.

To my surprise it was at 100% os capacity! It’s amazing how a well treated EV car can last!

It's not reasonable to assume that the battery cells in your battery pack haven't degraded over 115k km and 4 years. It's likely that the new usable capacity of your battery pack exceeded 120 Ah, so it might have degraded to 120 Ah which would be 100% of the nominal new usable capacity.

A U.S. company, Recurrent Automotive, monitors, with their owners' permissions, battery packs in thousands of EV's over the Internet via their cellular data radios. I participate in this program and receive monthly reports. Part of my August report is attached showing the degradation trend over time of all "comparable EV's" being monitored, whatever "comparable" means. For an i3, the charge level and Comfort mode estimated range are being monitored and averaged for each monthly report. Recurrent recommends operating within the 30% to 80% charge level range for maximum battery pack life (60% average during August for our i3).

The i3 battery management system (BMS) prevents the charge level from exceeding ~95% and decreasing below ~10%, so it provides some degradation rate reduction without decreasing the range excessively. The i3 displays charge levels relative to the minimum and maximum allowed by the BMS, so an actual 95% is displayed as 100% and an actual 10% is displayed as 0%, for example. The BMS can adjust the minimum and maximum charge levels, so these limits aren't fixed.

No matter how a battery pack is treated, its capacity will decrease over time and usage. Fortunately, the i3's 94 Ah and 120 Ah battery packs seem to be degrading quite slowly, especially when compared to some, but not all, i3 60 Ah battery packs.

 

[Gonville]

Congratulations!

Did BMW do the comprehensive battery capacity test that they do for battery capacity warranty claims? This test involves completely discharging and then fully charging the battery pack to measure the energy vended/consumed. This can take several hours and generally costs a couple hundred dollars in the U.S. Even after this test, some U.S. BMW dealers provide just a passed/failed result without a measured capacity which varies with temperature and with how fast the battery pack is charged/discharged.

It's not reasonable to assume that the battery cells in your battery pack haven't degraded over 115k km and 4 years. It's likely that the new usable capacity of your battery pack exceeded 120 Ah, so it might have degraded to 120 Ah which would be 100% of the nominal new usable capacity.

A U.S. company, Recurrent Automotive, monitors, with their owners' permissions, battery packs in thousands of EV's over the Internet via their cellular data radios. I participate in this program and receive monthly reports. Part of my August report is attached showing the degradation trend over time of all "comparable EV's" being monitored, whatever "comparable" means. For an i3, the charge level and Comfort mode estimated range are being monitored and averaged for each monthly report. Recurrent recommends operating within the 30% to 80% charge level range for maximum battery pack life (60% average during August for our i3).

The i3 battery management system (BMS) prevents the charge level from exceeding ~95% and decreasing below ~10%, so it provides some degradation rate reduction without decreasing the range excessively. The i3 displays charge levels relative to the minimum and maximum allowed by the BMS, so an actual 95% is displayed as 100% and an actual 10% is displayed as 0%, for example. The BMS can adjust the minimum and maximum charge levels, so these limits aren't fixed.

No matter how a battery pack is treated, its capacity will decrease over time and usage. Fortunately, the i3's 94 Ah and 120 Ah battery packs seem to be degrading quite slowly, especially when compared to some, but not all, i3 60 Ah battery packs.

View attachment 1363

Sounds like a good buy.

Just on the comments on age and battery degradation. Pretty much I understand that the charging mechanism or mileage doesn’t do anything to counter calendar degradation . That degradation in the i3 is deemed to be about 1-2% per annum so on this model after 4 years it will only be 4% and probably absorbed in the hidden top end buffer. Must try to get a source on this ‘calendar’ degradation although Bjorn Nyland winter testing seems to show the i3 right at the best of most cars he has tested.

 

[alohart]

Just on the comments on age and battery degradation. Pretty much I understand that the charging mechanism or mileage doesn’t do anything to counter calendar degradation . That degradation in the i3 is deemed to be about 1-2% per annum so on this model after 4 years it will only be 4% and probably absorbed in the hidden top end buffer. Must try to get a source on this ‘calendar’ degradation although Bjorn Nyland winter testing seems to show the i3 right at the best of most cars he has tested.

I'm beginning to believe that a warm climate accelerates the age-based cell degradation rate compared with a cool climate, maybe especially with 60 Ah battery cells. The battery cells in our 2014 i3 degraded ~25% over 7 years even though our i3 had been driven only 12k miles, ~3.5% per year. Even though we don't have extremely hot weather, we never have cool weather. The temperature where our i3's have been parked 95+% of their lives ranges from 73 ºF to 78 ºF which seems ideal, but maybe not. 60 Ah i3 battery packs in cool climates seem to degrade more slowly.

 

[Joff]

Even the older 94ah batteries that I have checked still have 100% or more of their original RATED capacity. They were under rated from the factory, so this does not mean they have no degradation. They do hold up really well though, and loss of capacity is not the serious problem that it is with the 60ah batteries.

 

[Gonville]

I'm beginning to believe that a warm climate accelerates the age-based cell degradation rate compared with a cool climate, maybe especially with 60 Ah battery cells. The battery cells in our 2014 i3 degraded ~25% over 7 years even though our i3 had been driven only 12k miles, ~3.5% per year. Even though we don't have extremely hot weather, we never have cool weather. The temperature where our i3's have been parked 95+% of their lives ranges from 73 ºF to 78 ºF which seems ideal, but maybe not. 60 Ah i3 battery packs in cool climates seem to degrade more slowly.

How was that measured? That’s always been an issue without the dealer full discharge and re-charge.

 

[alohart]

How was that measured? That’s always been an issue without the dealer full discharge and re-charge.

25% was my estimate based on the decrease of actual and predicted range when the range of driving conditions was small, the unreliable Batt. Kapa. max. decrease over many readings, BMS data displayed by the mi3 app, etc. I'm confident that my estimate was within ±5%, but it was never measured by a dealer or using ISTA.