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Joined: Thu May 28, 2020 12:58 am

i3 charging

Thu May 28, 2020 1:01 am

I'm confused about the charging system on the i3, specifically the dashboard/software controls.

I've set Level 1/2 at maximum. I have a 50 amp line, 40 amp EVSE from which the Tesla charges flawlessly.

I'm struggling to understand:

1) Charge time windows. I just want to set a charging window of 12 midnight to 5am, regardless of all other variables. Can it be done?

2) How do I know what my charging level is when plugged in? I'm specifically looking for an indicator showing that I'm drawing at 30+ amps (or up to 7+ kilowatts). Does the feature exist? All I can find is a graphic that says I'm charging. Not so helpful.

3) DC Fast: I plugged into our local DC Fast charger, but again, was not clear what the actual charge level was that I was experiencing. The DC Fast indicator icon did not appear, but there was charging occurring. Again, just not sure if it was Level 1 or 2 and if 2, the number of kilowatts I was at.

Am I missing something? Any help appreciated.

Posts: 427
Joined: Mon Sep 09, 2019 5:33 pm

Re: i3 charging

Thu May 28, 2020 1:45 am

Alas, you're not missing anything.

You can select your window ("tariff time slot") but you can't select it unless you have a departure time set.

If the car determines it can't charge to 100% before the departure time -- based on available current -- it will charge outside of the window.

Nothing in the car or on the app indicates charging current. You'll have to look at estimated time of charge completion and work backwards. For instance, I know my 94Ah battery gains approximately 10% per hour at L2 / 16A.

Yes, this system is pretty dang basic.
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Re: i3 charging

Thu May 28, 2020 1:07 pm

It's my understanding that the charging rate adjustment only works with the 120vac device delivered with the vehicle in the USA, not when connected to a 240vac device. That may change per market. It's there in case that receptacle you plug the thing into may be on a shared circuit with something else to help prevent from overloading the circuit. Say, it's plugged into the same circuit as your garage door opener...might work fine until you tried to open or close that door, or maybe use a saw, compressor, vacuum, or some other tool. It won't overload the EVSE, as the EVSE reports to the car the maximum it can deliver and the car adjusts itself to that, but potentially not if it was a shared circuit.

In the USA, the maximum EVSE charging rate is 7.4Kw. Power depends on the voltage supplied, so with the same EVSE device at a 208vac commercial input would provide less power than a 240vac line you may have in your home (power=volts*amps). Since the pilot signal from the EVSE announces how many amps, and not power it can provide, a 30A device at 208vac won't max the i3 out, but in my case, my 30A EVSE at my typical 247vac does.

The time slot for charging could be a little easier than the way they implemented it. It isn't all that clear. It also can be misleading, since, if you plug the car in while the charge is below a certain point, it will start to charge a bit, then stop and wait so that the battery doesn't sit at a low charge level when it could get cold and become damaged.

Last, the car does calculate, given the available data based on the pilot signal from the EVSE and its current state of charge when it will be finished charging nor does it actually show the current charging rate in amps or watts.

For less than about $30, I wired in a meter to monitor the power, voltage, and amps my EVSE was pulling. It's operational power is in the 20W range when activated (lights and contactor and logic), and maybe 3W when not (indicator lights and logic).

While I have the CCS input on mine, I've never actually plugged it into one. Probably should have before the warranty expired, but never found the need as I use it as a local runabout, as it was designed for, not a road car on longer trips so I'm always home to plug it in without intermediate charging along the way.

Keep in mind that the car does slow the charging rate down, regardless of the capacity of the EVSE or CCS unit you plug into as the batteries approach full charge. That's one reason why they rate the CCS charging times to 80% rather than 100%, as after that point, the heat buildup and charging rate come into play in trying to preserve the battery health. Level 2 charging, from what I understand, gets to a higher level before it starts to taper off partly because that slower rate (7.4Kw versus 50Kw rates) between level 2 and CCS differ. With an EVSE, it can get somewhere in the 90's percent range before it slows down. Also note that not all CCS units out there will max out the i3, either. While there are now some capable of up to 350Kw, the car won't use more than the 50Kw rate from it, and BMW offered some price leader 25Kw CCS units to dealers to soften the blow about installing them that you might see around. A DC power supply that big is somewhat expensive, and requires some major power line upgrades to be able to install.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

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Re: i3 charging

Thu May 28, 2020 3:45 pm

jadnashuanh wrote:
Thu May 28, 2020 1:07 pm
It's my understanding that the charging rate adjustment only works with the 120vac device delivered with the vehicle in the USA, not when connected to a 240vac device.
At least with the system software version that was installed on our 2014 U.S. BEV when it was new, setting the AC Level 2 charging rate to "Reduced" in iDrive did reduce the charging power. The Driver's Guide smartphone app, which is apparently tailored for one's specific i3 based on its VIN, states that the maximum "Reduced" AC Level 2 charging current for our i3 is 20 A. I haven't verified this in years, but I have no reason to believe that this has changed.

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

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