2014 i3 REx - Battery Degredation

[alohart]

I trusted them and drove off only to discover that my car had a maxed-out charge of 61 miles!!!

Seems like you've reported the Guess-o-Meter range estimate which is based on recent driving conditions, temperature, and other factors we don't know about. This estimate can be very inaccurate, so actual range is what matters. Has your actual range dropped significantly?

Isn't the E.P.A. rated range for a 60 Ah REx 72 miles? Driving conditions could easily reduce the predicted range to 61 miles.

Your battery pack's usable capacity is your actual range divided by your recent EV driving efficiency in mi/kWh which is available in iDrive. For example, if your actual driving range were 61 miles from full to empty and your recent EV driving efficiency were 3.5 mi/kWh, your battery pack's usable capacity would be 61 mi / 3.5 mi/kWh = 17.4 kWh. Your battery pack's usable capacity when new was ~18.8 kWh, so that would indicate degradation of (18.8 - 17.4) / 18.8 = ~7%.

 

[SCVi3RexSB]

Hello All,

I just purchased a 2014 i3 REx with 26,000 miles a couple days ago. I traded in a 2011 Nissan Leaf with range only down to 10 bars out of 12 and effective highway range of about 50 miles. I have now become concerned about the electric range on the i3 after full charging it to 64 miles of range which then dropped much more quickly than the Leaf or our 2013 Ford Focus Electric on my usual commute route.

After observing this quick drop, I started reading forum posts concerning battery degradation. I found my Batt.kapa.max is 15.9 kwh which would make about a 15% loss in capacity. I see that some have said Batt.kapa.max can fluctuate +- 2 kwh and others that said let the battery discharge and then recharge it full will give the best Batt.kapa.max reading for my car. I will be fully discharging it today to check the range extender anyway, so I will take another Batt.kapa.max reading after a full recharge.

Should I be concerned that I have a battery that has some excessive degradation? I have a day or so to return the car, so any responses would be appreciated.

Thanks,
Don

 

[alohart]

I found my Batt.kapa.max is 15.9 kwh which would make about a 15% loss in capacity. I see that some have said Batt.kapa.max can fluctuate +- 2 kwh and others that said let the battery discharge and then recharge it full will give the best Batt.kapa.max reading for my car. I will be fully discharging it today to check the range extender anyway, so I will take another Batt.kapa.max reading after a full recharge.

Another possibility could be that the charge levels of the battery cells in the battery pack vary considerably which reduces the usable capacity. The i3 battery pack's cells rebalance when the charge level remains very high for a considerable period. Unfortunately, BMW doesn't mention cell balancing anywhere that I've been able to find, so I don't know when balancing can occur (must the charge level be full?) and how long balancing might take (hours, days, weeks?).

The charge levels of the cells could diverge if the previous owner rarely charged fully and left the car fully charged for extended periods. But then leaving a battery pack fully charged for extended periods isn't ideal for battery pack longevity even though "full" is really only ~93-95% of the absolute 100% charge level.

Should I be concerned that I have a battery that has some excessive degradation? I have a day or so to return the car, so any responses would be appreciated.

You haven't added your location to your user profile, so I don't know where you are. However, in the U.S., the battery pack is warrantied not to lose more than 30% within 8 years of the car's original in-service date or before the car has been driven 100k miles (maybe 150k in California). But I would not want to drive with limited EV range for years waiting for the usable capacity to drop below 70%.

If I were you, I would require the seller to have a BMW dealer test the battery pack's capacity and issue a report. If the seller won't do that, I would return the car.