How best to charge

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Bybmwi3

Member
Joined
Aug 8, 2021
Messages
5
Sorry new to ev and i3 just git a 2017 bev and wondering if its best to just keep plugged in or let charge drop to 20% then plug in to 80% keep been told to do both🤨
Also was wondering will car drive if you forget to unplug ( yes im that new)
Thanks
 
No, the car will not move if you forget to unplug it. You will get a warning message on-screen. If you unplug and leave the flap open, the car will move, but it will warn you that it is open.

You don't need to charge to 80% to 'protect' the battery. BMW battery management is pretty good. Even when you charge to 100% you aren't charging to 100%, as the battery management software has set aside a percentage of the battery that can't be charged, as a buffer. One advantage of charging to 100% along with setting pre-conditioning, is as the battery approaches 100%, it will initiate battery cell balancing, which helps maintain overall battery health and range.

On the Facebook i3 world wide group the most common answer for your charging question is: "A B C", or 'always be charging". Either way works out the same. Eg. use 15% of the battery per day and charge every day, or use 45% of the battery over three days, and charge on the third day, is exactly the same thing as far as the battery is concerned.
 
I wouldn't keep the car fully charged for extended periods of time. There are enough data showing that keeping the battery at a high state of charge shortens its life. As MKH said, the i3 battery is not actually fully charged when it shows 100%, so it will not suffer as much degradation as a phone. I wouldn't worry about the low side, the battery will start degrading only when severely discharged, and cars never get to this state.
You got two advices here as well :)
 
I'll just add that there's nothing novel about BMW's battery that makes it immune from conventional "battery best practices," which is where the 80% figure comes from. I think it unfortunate that BMW hasn't provided us a way to cut-off charging at some SOC lower than 100%, like every other EV manufacturer does, but I can guarantee you that BMW's 8 year old technology does not contain some "secret sauce" that has escaped every other auto maker.

Whether always charging to 100% will have much impact on your battery's long-range health or even if you'll own the car long enough to be affected by it, who knows -- all batteries degrade over time and cycles and there are other factors at play. I'm just approaching this from the "playing it safe" angle and get along just fine with 80%. I also don't stress when I charge it to 100%, and will do so if I need it.

As for the buffer, it's true the i3 battery, like most every other current generation EV, has a bit of buffer, but it's split between the top end and the bottom end. There's about 5% room at the top, and a little more at the bottom, dependent on which generation battery we're talking about.
 
Here is one report on EV battery 'life', including BMW i3

https://insideevs.com/news/334057/bmw-i3-long-term-battery-capacity-report-better-than-expected/
 
Preconditioning is the car warming the battery to 70-something degrees, its most efficient operating temperature, prior to a scheduled departure time. This is only done while plugged in, and maximizes the battery's output. Cold batteries are less efficient.
 
What eNat posted :D

The car automatically preconditions and cell balances when a) It is plugged in to charge, and b) you have set a departure time. This is all set up in the idrive menu - you can select days of the week and times for your departure, then what the car will do, is charge most of the way up when you first plug it in, then finish charging while either warming or cooling the cabin starting around ten minutes before your set departure time - so you leave with a nice cabin temp ie 'pre-conditioned' cabin, and optimum temperature HV battery, with the bonus of the car doing HV battery cell-balancing too - which provides for the best battery output. If one or two cells are lower in charge than the rest of the pack, you get the range and output of the lowest cells overall. Cell balancing reduces that problem, as possible.

The car will precondition when not plugged it, but won't cell balance.
 
Here is one report on EV battery 'life', including BMW i3

https://insideevs.com/news/334057/bmw-i ... -expected/
Mark H.

This is a brilliant link. Thanks Mark H. Loads of info on the i3 by someone that has done a bit more analysis than I ever would

😂

Cheers, Finchie
 
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