BAT QUESTION FOR TOM

[kullenberg]

A question for Tom: What degrades the bat. more; mileage or time? Since I drive so little (4000 mi per yr.) time would be determining factor for me. Thanks

 

[dennis]

A question for Tom: What degrades the bat. more; mileage or time? Since I drive so little (4000 mi per yr.) time would be determining factor for me. Thanks

I know the question was placed to Tom... But any of the higher mileage Active E drivers can speak about the battery degradation...

Kullenberg, Since you're in Long Beach, California and not Long Beach Island, NJ the seasonal temperature changes won't matter much... Now had you been in you're in Long Beach Island, NJ the seasonal temperature changes will mess with you as well (as far as the cold)

I'm above 50,000 miles on my Active E with less than a month to go to return my vehicle to Long Beach BMW and I can say that I noticed battery degradation closer to 40,000 miles. I often drive 102 mile days Long Beach-Culver City-Glendale and Back on carpool days with my better half and noticed that earlier the SOC was closer to 50-55% in the early miles and now I get closer to 33-38% and that's at milder summers that we've had in the past 23 months.

I don't know if Todd C is on this board since he's decided to move to a RAV4EV, but he is also another higher mileage Active E driver in Long Beach, CA... He can attest to approx. 44,000 in his two years with his Active E.

[On another note, do we know whether BMW i moved on adding an SOC for US i3s yet?]

Additionally, if you are looking to get your car from Long Beach BMW, get it serviced there as well... Between Todd and myself, I would think that the service guys at Long Beach BMW have one of the most experienced technicians for servicing the Active E (which should translate to the i3 well at least for the transmission and batteries.)

Hope that helps (since I assume that Tom is asleep at 12:32am Eastern (though I should be, since I'm in Miami, and not Long Beach today).

 

[kullenberg]

Dennis:
Thanks for the reply. It looks like there is some degradation with mileage. I still don't have a feel for what time will do. For instance; in 3 years I would barely put 12000 miles on it. My 128i has 8200, going on 3 years.

I agree about LB BMW. I get my 128i serviced there and have been well satisfied. I didn't buy it there, as my USAA buyer program showed South Bay to be the cheapest.. I think LB BMW has improved greatly over the last few years. It may have changed hands.
Regards
Pat

 

[woof]

It looks like there is some degradation with mileage. I still don't have a feel for what time will do.

To be clear, it's not mileage per se, but charge/recharge cycles that degrades the batteries.

As for degradation over time it depends on the chemistry of the battery, which for the i3 we really don't know as that information is proprietary. All we can do is assume there is some, and that it'll be worse at 100% charge, and at elevated temps. Presumably the i3 BMS will protect against both extremes, and one need do nothing other than plug it in when you can and let BMW take care of it.

For a good treatise see:
http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

--Woof!

 

[dennis]

It looks like there is some degradation with mileage. I still don't have a feel for what time will do.

To be clear, it's not mileage per se, but charge/recharge cycles that degrades the batteries.

As for degradation over time it depends on the chemistry of the battery, which for the i3 we really don't know as that information is proprietary. All we can do is assume there is some, and that it'll be worse at 100% charge, and at elevated temps. Presumably the i3 BMS will protect against both extremes, and one need do nothing other than plug it in when you can and let BMW take care of it.

For a good treatise see:
http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

--Woof!

That must be it... I charge twice a day (often)... I thought that the i3 shares the batteries and drivetrain with the ActiveE (albeit with less cells).

On other battery stuff for BMW. Compared with Tesla, it seems to me, though it could just be the way the algorithm works, at there is no noticeable vampire loss for the Active E when parked unplugged at a parking garage for a few days vs. either the Model S or Roadster.

 

[TomMoloughney]

It's really a combination of everything. The age is probably one of the biggest contributors to capacity loss, but so are the number charging cycles, deep discharges, how ell you've maintained the battery, etc. I did a story for BMWBLOG on this a while back if you are interested:
http://www.bmwblog.com/2013/04/25/understanding-battery-capacity-loss/

 

[Muhv]

http://youtu.be/pxP0Cu00sZs

Correct me if I am wrong, but it seems to me that i3 will drop into the same box with Nissan and Volt Lucky me, living in a relatively cold country.

Sum: charge your battarey quickly (less corrosive) and keep out of sun, as BMW is useing wrong chemistry.