Deutsch100
Posts: 195
Joined: Mon Sep 30, 2019 2:28 pm

Re: bmw i3 important question

Sun Mar 28, 2021 9:10 am

Fordychap wrote:
Sat Mar 27, 2021 8:48 am
By the time I drove to work this morning, my car had 155 miles on pure electric and in EcoPro it showed 167 miles :) It seemed letting the battery deplete, run on REX, charge on Level II and leave it plugged in for at least 6 hours past complete charging for a battery balance did the trick!! YAY!

Bask in the heat of 66F, ha ha ha LOL. You would D I E in summer here in Southern California. 90F is considered cool, and many weeks (or months) see 100-110F!!!!
That's fantastic news. Seems like the REx and Level 2 charge sorts that idiosyncrasy out - I can see you doing that a little more often from now on...

As for weather - I'm definitely a northern hemisphere, Viking descended, Westmorland (an old English county) man...
Not only do we still count sheep in the old base 20 way (Yan, tan, tethera) but at anything above 24 degrees Celsius (75 F) and I start to melt fast...
Shirt sleeve weather (when working) here on the farm is anything over 10 degrees C (50 F). I like it cool. I'm not one for cooking myself on a beach...

In the late 80's I spent quite a while in San Diego (about 5 months in total) and remember Mission Bay, the old wooden rollercoaster, OMBAC DTL competitions , cold Pacific Beach (PB) Blonde beer and the girls.... I do remember it was warm, and only seemed to rain at night... Happy memories.
I am 100% the same. I am 100% Teutonic myself. Anything above 20-24C and I think it is hot, LOL. San Diego is beautiful, but for So. California standards....very cool and tempered. I am in Calabasas, CA and our June-Oct is usually 33-45C!!! Last August we had several days of 49.5C!!! I thought I would D I E ;)
2020 i3S Rex; Capparis White

Deutsch100
Posts: 195
Joined: Mon Sep 30, 2019 2:28 pm

Re: bmw i3 important question

Sun Mar 28, 2021 9:13 am

alohart wrote:
Sat Mar 27, 2021 11:25 am
Deutsch100 wrote:
Thu Mar 25, 2021 4:07 pm
By the time I drove to work this morning, my car had 155 miles on pure electric and in EcoPro it showed 167 miles :) It seemed letting the battery deplete, run on REX, charge on Level II and leave it plugged in for at least 6 hours past complete charging for a battery balance did the trick!! YAY!
The i3's passive battery cell charge level balancing is implemented using resistors that discharge those cells with the highest charge level. This occurs whenever the high-voltage system is off (e.g., when an i3 is off, not charging, not preconditioning). Leaving an EVSE plugged in would only increase the battery pack's charge level if the balance had been so bad that the charge level had dropped during balancing. The balance resistors have such a high resistance that balancing is very slow, so the balance shouldn't have improved noticeably in 6 hours.

The fact that the high-voltage system is typically off most of the time means that cell balancing is almost always occurring. As a result, few i3's likely have battery packs that are significantly unbalanced. Some Android smartphone apps as well as BMW's ISTA+ service software display the maximum and minimum voltages in the battery pack. When some i3 owners have posted screen shots showing maximum and minimum cell voltages, I've never seen much difference in these voltages which means that the cell charge levels have been well-balanced.

What is more likely to have occurred in your case is that the charge level calculation was calibrated when you allowed the charge level to drop to a low level followed by charging fully. This can occur with many rechargeable battery powered devices that calculate charge level using the current flow in and out of the battery. Due to unmeasurable internal self-discharge that occurs with all battery cells, the charge level calculation gradually loses accuracy. Discharging to a low charge level reveals this inaccuracy because the voltage at the low calculated charge level isn't what it should be. The calculated charge level is then reset to be consistent with the voltage. So as with any rechargeable battery powered devices, the charge level should be allowed to decrease to a low level periodically followed by a full charge.
A-ha. Once again Art knows best and explains it clearly and perfectly. Thank you!!! :) You are such a valued Member on this page!
2020 i3S Rex; Capparis White

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