greenlion
Posts: 9
Joined: Tue Feb 05, 2019 10:56 am

leaving i3 rex overnight with low battery

Fri Feb 22, 2019 10:37 am

HI all , was wondering if leaving the I3 Rex overnight with less than 10% batt could possibly damage the batteries ? I came home last night with rex running and waited till it shut off then powered down car for the night ,is that not a good idea ?should i be charging ? thanx in advance :D oh ya 17' rex

alohart
Posts: 1675
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: leaving i3 rex overnight with low battery

Fri Feb 22, 2019 4:25 pm

greenlion wrote:HI all , was wondering if leaving the I3 Rex overnight with less than 10% batt could possibly damage the batteries ? I came home last night with rex running and waited till it shut off then powered down car for the night ,is that not a good idea ?should i be charging ?
Leaving a Li-ion battery pack at a low charge level for hours at a time isn't best for its longevity, but doing so once wouldn't noticeably degrade the battery cells. To minimize the cell degradation rate, don't leave a cell at a low or high charge level any longer than necessary.
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

jadnashuanh
Posts: 4487
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: leaving i3 rex overnight with low battery

Fri Feb 22, 2019 9:56 pm

You shouldn't do that!
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

gt1
Posts: 321
Joined: Sat Nov 07, 2015 7:31 pm
Location: Baltimore

Re: leaving i3 rex overnight with low battery

Sat Feb 23, 2019 6:49 am

I was under the impression that a low SOC is better for the battery health than a high SOC. A long term low SOC storage will eventually discharge the battery to dangerous level, but overnight should be fine. I usually charge before the departure rather than on arrival.

AndrewDebbie
Posts: 171
Joined: Sun Aug 04, 2013 10:37 am
Location: Anglesey, Wales, UK

Re: leaving i3 rex overnight with low battery

Sat Feb 23, 2019 8:30 am

The owner's manual for my 94Ah i3 says

"When the vehicle is stand around for several weeks, where possible stop with a fully-charged high-voltage battery"
"Do not leave the vehicle for longer than 14 days if the electric range is less than 10km" (6 miles)




LEAF owners manual says to charge the battery as soon as possible if it is under 20% SOC. The manual says storing the car under 20% will damage the battery.

Over in the LEAF side, it is common practice to store the car between 50-80% SOC. LEAF has a different fully charged safety margin than i3. Storage at 100% isn't good for a LEAF pack.
2014 LEAF 24 (gone)
2017 LEAF 30 (gone)
2018 Mazda 2 (Debbie's)
2018 i3s 94Ah Rex

jadnashuanh
Posts: 4487
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: leaving i3 rex overnight with low battery

Sat Feb 23, 2019 5:19 pm

It's the combination of cold weather and low battery SOC that is the issue...if it were warmer, it wouldn't be as much of an issue. Note, if the battery is cold soaked, it also may take awhile for the management system to warm it a bit before it will reach maximum charging rate.

FWIW, I've 'lost' 10-miles of range just from the temperature drop considerably (from my garage to outside) overnight. It could be enough to mess with the 12vdc battery, too, which doesn't like cold. The system won't recharge it unless plugged in, and that's necessary to run the computers.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

gt1
Posts: 321
Joined: Sat Nov 07, 2015 7:31 pm
Location: Baltimore

Re: leaving i3 rex overnight with low battery

Sat Feb 23, 2019 5:45 pm

I completely agree about the long term storage- self discharge and periodic wake ups would eventually drain the battery, but the question was about an overnight delay. Charging before departure in a cold weather is preferable because it will warm up the battery.

Boxbrownie
Posts: 70
Joined: Sat Sep 06, 2014 10:21 am
Location: Pastyland, UK

Re: leaving i3 rex overnight with low battery

Mon Feb 25, 2019 8:45 am

BMW engineer into the system a buffer at both top and bottom of the the traction battery to avoid just such a problem occurring.

Overnight depleted will be fine, just don’t leave it for long as the manual states.
Best regards........David

If anything in my post offends you please let me know, I may wish to offend you again. ;)

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