asthorman
Posts: 3
Joined: Fri May 31, 2019 12:36 pm

Limiting total charge % - hidden feature?

Thu Jun 13, 2019 9:58 am

I haven't seen this discussed before, so I thought that I would mention it.

When I set both the 120v and 240v charging to their lowest setting, my i3 automatically stops charging at 85% or 87% capacity. Like others, I've been somewhat disappointed by the inability to avoid charging to a full 100%. However, I seem to have accidentally stumbled onto a hidden feature, either that, or my i3 is not working properly :D :D

Since I live in Phoenix, and my garage is regularly over 100 degrees this time of year, I like being able to leave the i3 plugged in all night to keep the battery cooling system active. This seemingly hidden feature allows me to check both boxes, keeping the battery cool, and not charging to a full 100%.

Thanks!
Andrew in Phoenix, AZ
2017 BEV

gps1539
Posts: 31
Joined: Tue Jul 03, 2018 3:08 pm

Re: Limiting total charge % - hidden feature?

Thu Jun 13, 2019 1:18 pm

Does it charge to 100% if you set the higher charging rates?

asthorman
Posts: 3
Joined: Fri May 31, 2019 12:36 pm

Re: Limiting total charge % - hidden feature?

Thu Jun 13, 2019 1:54 pm

gps1539 wrote:
Thu Jun 13, 2019 1:18 pm
Does it charge to 100% if you set the higher charging rates?
Yes, when I change the settings back to 'Maximum', it will charge up to 100% like normal. The first time I noticed this, was after receiving a message on the Juicenet app saying 'Energy limit reached' or something along those lines.
Andrew in Phoenix, AZ
2017 BEV

vreihen
Posts: 87
Joined: Tue Apr 30, 2019 4:55 pm
Location: Orange County, NY (FN21vm)

Re: Limiting total charge % - hidden feature?

Thu Jun 13, 2019 2:26 pm

I wonder if the reason for this happening is because BMW's charge-tapering function is clashing with J1772's minimum Level 2 supply current of 6 amps at the car's lowest charge settings?

The right side of this graph shows my i3 charging at 16 amps, and you can see the taper-down as it approaches full:

Image

(The left two traces on the graph are my DW's new Kia Niro EV, which does not appear to have a graceful taper-down in its charging system judging by the vertical line when it completes.)

Anyway, this may explain the "energy limit reached" message from the EVSE if it happened as the car's demand dropped below 6 amps.....
2015 BMW i3 BEV, Giga World, Tech and Driving Assistant packages, 15K miles

asthorman
Posts: 3
Joined: Fri May 31, 2019 12:36 pm

Re: Limiting total charge % - hidden feature?

Tue Jun 18, 2019 3:01 pm

More investigation is required. My i3 is back to charging to 100%, despite the charge settings adjusted to the lowest possible for 120 and 240v. I am somewhat disappointed as I liked being able to keep the vehicle plugged in all night to allow the batteries to self-cool in my hot garage, while simultaneously not letting the vehicle sit at 100% for hours and hours. I will update this thread if anything changes!
Andrew in Phoenix, AZ
2017 BEV

n1o2c3a4c5h6e7t
Posts: 17
Joined: Wed May 01, 2019 12:35 pm

Re: Limiting total charge % - hidden feature?

Wed Jun 26, 2019 6:43 am

What is the point of running the battery cooling for hours a day when you're not using it? How much energy does that use? Are you suggesting that this increases the battery's longevity?

I also doubt that a closed garage can get to 100 degrees overnight, and perhaps not during the day either. Shade can take 20 degrees off the ambient temperature in the desert.

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