Battery preconditioning in cold weather

I did not realize you were using a smart EVSE to control your charge window.

I think what might be happening in your case is the EVSE is coming on before the car's charge window (maybe by just a second or two), and the SE will start charging immediately if plugged in during the charge window, which is what you'd effectively be creating with your smart EVSE.

Try having your car's charge window start a few minutes after the EVSE energizes.

 

In my experience, the app always advertises that it will begin charging at the start of the time slot and the car always advertises that it will be completely charged by the departure time--regardless of the car's state of charge and how much charging time is actually needed. In practice, the car begins charging well after the start of the time slot and invariably reaches 100% a few minutes before the set departure time (even though the app will often report it will be done by a few minutes after the departure time once it actually starts charging).

 

So - I took some battery temp measurements last night and this morning on my i3 for reference. I know it's not a Cooper SE, but maybe you guys would find it informational/useful since they share the same powertrain/battery.

This is from my 2018 BMW i3 REX (33kWh battery). My partner drove it to work yesterday (short, 15mile commute). I went out and plugged it in around 5:45PM at 77% SoC (charging was delayed because I didn't realize I had accidentally locked the charger, otherwise I have the car set to start charging immediately). After I found my bluetooth ODB adapter (VEEPEAK brand) and an my old Android phone with the "electrified" app, I measured the battery temp at 6.4C. SoC had risen to 78.3% per the app and outside temp was registered as -2.5C (this is from the app, I'm guessing it pulls from the cars registered outside temps since actual outside temps were 20-23F, -6 to -5C).



Went back out at 7:53PM to check on things and battery temp was now 6.1C, 94% SoC, and outside temps registered -2.0C (actual outside temps are -5 to -6C).



I had a departure time set for 5:45AM via the BMW App, with pre-conditioning on. The i3 had finished charging to 100% at 8:48PM. Temps last night hovered around -6C to -5C.



I went to leave the house around 5:45AM. The i3 had pre-conditioned and the cabin was nice and toasty, as usual. I saw the same power draw info from my EVSE as I usually have. A short small draw around 2:45AM and then normal pre-condition started around 5:15AM with a max draw around 6.42kW at the start, it was still pulling from the EVSE when I left around 5:45AM.




After a few minutes of trying to get my phone reconnected to the ODB dongle it was now 5:49AM. The battery temp was 10.6C, 100% SoC, and outside temp measured -4.0C. This shows me that even at 100% SoC the i3 is indeed doing some battery pre-conditioning. Maybe not warming it up as much as it should (or that would be most beneficial), but it's better than nothing.

For some additional data - about 33miles into my 46 miles commute to work I registered a battery temp of 14.3C, 65% SoC, and outside temp of -6.5C.



I drove in "Comfort" mode (Mid mode on the Cooper SE), with climate set to 66F. It was a 51min/56mile commute with an average speed of 55.7mph (this is from my trip meter so probably more like 58-60mph average, it's almost all highway with cruise at 67 and a small bit of 76). I arrived at work with 50.1% SoC and a battery temp of 15.3C.



I'm very curious to know if Cooper SE owners would see the same results. I'd assumed they would since the i3 and SE are fairly similar. Hopefully this helps some of you with additional information/data.

 

I always make sure that the car is fully charged just before I leave. If I want to leave at say 7 AM I set the charging window to 6:00-7:00 AM. This obviously isn't enough to fully charge the Mini, but the software is always making sure that the car is fully charged before departure - meaning that it'll start charging as late as possible. So by doing this, the car is fully charged and the batteries warm just when I need to leave. I never experience loss of power even in -10c if I do this.

 

So we’ve come to the conclusion that even when the plugged in mini is preconditioning the cabin, it is slightly preconditioning the battery. It may not be in the same vein of a Tesla pre-con heat pump flow, but it definitely statistically significant increase in battery temps from “low cost charging” for daily winter use.

 

I have been using the scheduling feature for a week now and notices that is pauses and charges the last 5% just before your scheduled time to leave. This is the way it “preconditions” the battery before journey. The climate and comfort is done separately at the same time it finished the charging. Quite smart I think. Utilising the actual charging of the battery to get it warm for the journey.


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When you say scheduling, are you doing the low cost option too? Or just scheduling while doing “charge now” option? Would be much easier if we don’t have to do low cost. We are flat rate here.

Thank you.

 

My understanding is the i3 has battery warming, but for whatever reason MINI decided the cost of that wasn't justified. From my experience I believe that's mostly true, only in extreme below-zero temperatures do I see consistent drop in e-power. And even then I don't really notice any driving difference.

 

I don’t know what you mean about low cost charging as I just have a fixed price contract constantly. I schedule my charging from 0000 - 0700, however my scheduled departure time is later.

What I notice in the morning, no matter what, my car is finishing charging around 0715-0730
Just before I am about to leave.

So essentially the car is preconditioning bu charging at the last minute.

This only happens when you have a schedule charging and departure time set up


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If you want scheduled charging, you can always set your low-cost charge window to the whole day, like 00:00-23:59. If you have a flat rate, the only advantage to using the low-cost window is if you want to control when the SE reaches full charge. For example, if you want to have it reach 100% SoC near a 7am departure time, set your charge window to something like 19:00-07:00. Remember that the SE will start charging immediately if it's plugged in after the start of the window, otherwise it will delay until the end of the window.

Cabin climatization is separate from charging, for that you need to set a climatize schedule and turn automatic climatization on.

 

Two weeks into ownership and I'm getting a little concerned about low temps, especially if the SE has no battery warming tech like most other EVs. Lot of discussion here about battery performance in freezing conditions, but what is the consensus about degradation/damage? The last two nights here got down to between -10F and -15F. The car has been parked outside and plugged in to 120V (level 2 has to wait until we bring new service to the house in the spring). First night it continued to charge, but last night the car sat at 100% SOC, so no current. This morning I precondition the cabin while plugged in, and then made a short trip with 30% available traction power. This came back up, of course.

Anyone experienced any permanent drop in battery capacity? I know @Puppethead has spent a lot of time in the extreme cold. Is there a way to monitor degradation? Eek!

 

For our Honda Clarity, someone figured out how to create an app that works with an OBDII dongle to extract the battery capacity signal Honda uses to decide if your battery has degraded enough for a warranty replacement. No one on InsideEVs Clarity forum has come anywhere close to that level of degradation.

@Carsten Haase, do you know if the app you use can reveal the battery capacity? Does anyone know how a MINI dealer determines if a MINI Cooper SE's battery qualifies for a warranty replacement?

 

I've driven over 28,000 miles and have no signs of degradation, now in the middle of my SE's second winter. The battery is warranted for 100,000 miles and I believe it's 80% capacity to be considered a failed battery (I haven't looked at the paperwork since I got the car).

I was pondering the degradation issue today. Since the battery is actually 32.6 kWh and only 28.9 kWh is usable, that's almost 13% of reserve buffer relative to the 28.9 kWh. Would any degradation be taken from some of that buffer, keeping the 28.9 kWh available for longer?

I don't know much about battery chemistry, but I've always been under the impression that cold slows down battery reactions and it's high heat that actually causes damage.

 

I'm not Carsten, but here's what the "mi3" app shows when reading my SE: