BMW Connected Feature

[BobB]

We are in the middle of a 24 Hour Test drive of a 2017 i3. I have downloaded the BMW Connected app for the iPhone, and I am able to see the status, lock and unlock the doors, etc. but I do not see a place where I can choose to stop charging (say for example when I see that it is above 80%). Is it possible to use the app to tell the charger to stop charging the A3 while it is plugged in? Thanks.

[eNate]

Nope, alas, this feature is not available through the app nor in-car.

[BobB]

Thanks for the quick reply. Very disappointing that you can’t remotely stop charging for those of us wanting to follow good charging practices.

As an aside, we are absolutely loving the i3! Can’t wait to find the right deal and start going electric.

[jadnashuanh]

FWIW, BMW has some automatic buffers in their battery logic both at the top and bottom. Tesla, under some circumstances, will let you use more, and limiting maximum charge most of the time has some advantages. Unlike say a cell phone, the smarts in an EV disconnect the incoming power once they feel the battery is sufficiently charged, so sitting on a charger, pushing power into a full battery is not an issue. And, BMW does do some cell balancing on occasion, so once it initially stops, lets things settle, it may turn back on and cycle a bit to balance things out.

[JohnKelly]

It is completely unnecessary to second guess the engineers who designed the car by stopping charging below 100%. With the built in battery management software, upper and lower limits on the batteries are designed in. It is like only filling a gas guzzler up part way. The software does not allow a true 100% on the battery so you are just limiting your range for no reason. Makes no sense.

[eNate]

John, no offense, but speak for yourself.

For instance, I get to charge for free at work, so it makes total sense that I might want to stop charging so as to leave home at 70%, knowing that I'll get to 100% at work.

Secondly, the i3 only leaves about 5% buffer at the top. So while true that 100% isn't really 100%, it's still far more than 80%. It's clear "BMW engineers" favored user simplicity over battery longevity, and just because they planned it that way doesn't dismiss some universal truths about battery technology.

Those of us who don't need 100% all the time and plan on keeping our i3s for the long run may want the option as a hedge against degradation.

I don't see why you need to be so dismissive and condescending with the "makes no sense" editorial to a new member's entirely legit question.

[jadnashuanh]

On something like a cellphone or a laptop computer, yes, the battery will last longer if you never charge it to 100%, or leave it on charge for a long time, but an EVSE and an EV do not leave the power connected...the incoming acv is totally disconnected once the vehicle thinks it is as charged as it should be.

The battery chemistry, type, and configuration all play into what works best. Personally, when I get home, I plug in and unplug when I next leave.

[eNate]

Jim, part of the dilemma is there is so much contradictory, often incorrect, info on batteries.

An example? Right in your comment! Today's laptops and phone have very advanced battery management and they won't continue to apply a charge if left plugged in. Simply put, if they're charging lithium ion or lithium polymer batteries, they can literally explode if not charged correctly. And yet that myth persists, probably from the Nicad constant current days when that was common practice.

On the flip side, you have very reputable sources such as Tesla or Shimano throwing out figures ranging from 70% to 90% charge ceilings to maximize battery longevity.

It's impossible to talk specifics when there are so many generalities, but there's consensus that heat is bad and true 100% SOC isn't optimal. It's clear that an owner who wants to live life under 80% to keep degradation at bay certainty, at the minimum, is doing no harm.

[jadnashuanh]

BMW does a few things (probably more) to help maintain the batteries' lifespan.
- active heating/cooling to keep them within a safe range
- limit the min/max of use usable versus factual SOC
- tapers the charge both at the beginning if hot or cold, and at the end to help prevent thermal problems and overshooting
- limits the maximum duration of maximum power allowed (most people probably never experience that)

They believe enough in them to put an 8-year warranty in the USA. Now, yes, on something like an i3 with the CFRP frame, plastic panels, and electric motor, you could likely keep it beyond that time, but the state of the art may very well prompt people to get rid of it before the batteries actually become a major factor of ownership.

The only way to probably limit the max charge level on an i3 would be to have a programmable EVSE that you could estimate when the charge level would get where you want, and tell it to turn off, or have a home automation system to cut power to it. MOst EVSEs will recover from a power interruption, but not all, so double check yours first. Some require you to remove the plug and reinsert it to restart its sequence.