Winter battery performance

You need a 3.6-kW EcoFlow Delta Pro battery in the back of your SE--it costs only a dollar a Watt. That's assuming you can muscle the 99-lb beast into the back of your SE.

 

You found a bug in my calculation! I see where I went wrong. My calculation is only working when the starting battery % is 100% (which - for my trips - I almost always start with 100% charge when I'm doing longer trips and use the shortcut, so I never saw this bug kick in) I will work up a corrected version and post it on my youtube video description and here and the Range forum thread. Thank you for pointing this out!

 

Last time I was at MSP (a year ago), they had blocked off the upper floors of the parking ramp so there was no access to the chargers. But the nearby IKEA has some chargers, and their parking is an big flat enclosed area, so I could drive around there until I ran out. I can easily push the SE to the charger, assuming the wheels don't lock when it stops.

 

My formula error was assuming that the battery capacity is always 28.9 kWh. But if you are starting with less than 100% charge, I need to calculate a new starting battery capacity based on that starting % charge.

I believe the correct calculation would be:

MILES-DRIVEN = 51
START-CHARGE = 70%
END-CHARGE = 11%
START BATTERY CAPACITY (kWh): 28.9 kWh x (start-charge) = 28.9 x .70 = 20.23 kWh
CHARGE-%-USED: 1 - (.11 / .70) = 1 - .1571 = 0.8429 = 84.29% of the starting charge was used on the trip
BATT-CAPACITY-USED (kWh): 20.23 kWh x .8429 = 17.0510 kWh used on the trip
BATT-CAPACITY-LEFT (kWh): 20.23 - 17.0510 = 3.179 kWh
mi/kWh = (MILES-DRIVEN / BATT-CAPACITY-USED) = (51 miles / 17.0510) = 2.9910 mi / kWh
ESTIMATE RANGE = (BATT-CAPACITY-LEFT x mi/kWh) = (3.179 kWh x 2.9910 mi/kWh) = 9.5084 miles left

 

That seems like a lot of calculations but maybe it's just the format?

(Start%-End%)*28.9kWh = Capacity Used
Miles Driven/Capacity Used = Efficiency
Efficiency *28.9kWh = Total Range
End% * 28.9kWh * Efficiency = Range Remaining

 

These 60ish mile total range estimates are horrific…
I get that it’s extreme cold being MN and the like but at presumably freeway speed cars like the Mini with tiny batteries seem a real masochistic choice, you have to be really committed!
That said the 80 miles range or so not on the freeway is more comforting.

I never envied your guys who live with such cold winters, I’m doubling down on that view now!

 

This is one morning last week. I-89 through the green mountains. After 3 weeks and about 1200 miles, much of it in weather like this, I have some impressions, which I'll post soon. Mostly good! For now, I'll observe that by far the biggest hit on range with super low temps is resistance heating of the cabin. My GOM is an extremely pessimistic creature based on what it's seen so far. Still, 2.8mi/kwh overall in the coldest January for some years is pretty impressive!

 

I'm actually extremely impressed with the SE's performance in extreme cold weather. From what I've heard of Teslas they lose a much higher percentage.

 

That seems much closer to what the SE was showing.

 

I remember that day. Freaking finals week was delayed. Windchills were like -40 to -45 IIRC. It's also been in the single digits a few times this week. Big fat 1 today. Single digits are not uncommon here, nor is below zero. We don't linger there long though. Or rarely. Been living here since 1985 though so I've seen a ton of winters here. Before that NW OH with more snow.

Like a friend who grew up here but moved away in the 90s claims we get no snow. Oh so that's why we had snow days for snow last year. It happens but nothing lasts.

If you drove a little further outside Cbus it would've been -1. We hit single digits commonly. Last winter was warmer than usual as a whole.

 

Ironically, my winter performance is slightly better than the summer performance. In winter, our normal daytime temp is around 20-25C, so basically no heating or cooling is needed. In the summer it is normally between 30 and 40C, so the air-con is on all the time. There is only 0.1kWh/100km in it, but winter is 12.4, and summer is 12.5 . The colder, more dense air is offset by the lack of aircon.

 

It still works! But this morning was the first time the GOM was overconfident. 35 miles later I was at 4%

 

Cold weather means nothing to the SE batteries! Well, okay, maybe drop in e-power.

I decided to do a pure cold-weather driving test this morning. It was -3 ºF, not as cold as I was hoping for but I decided cold enough. I drove my regular ~40 mile commute completely in green+ mode (no heated seat either) to eliminate heating as a drain on the battery. I was pretty cold at the end of the 1.5-hour drive, having not worn my arctic expedition gear. Here's what MiniEVRange showed at the end of the trip:

***********************************
Feb 4, 2022 at 09:39 ** Driven: 37.8 Mi ** Start-Batt: 100% ** End-Batt: 73% ** Mi / kWh: 4.84 ** Range Left: 102.11 Mi ** Total Range (From 100% charge): 139.91 Mi ** Total Range (From 100% charge): 139.876 Mi

4.84 mi/kWh at -3 ºF! That's summer weather efficiency. No speeds above 60 mph, about half the distance at 55-60 mph. Car was fully charged about an hour before leaving, with climatization, and 100% e-power.

This confirms my hypothesis that heating uses a lot of battery in the winter. I guess the next step would be to try these runs at various cabin temperature settings.

 

That is impressive performance, and stalwart testing in Green+ for your body. It definitely helps with the < 60 mph, as well.

 

I think the resistive heaters for the battery thermal management system might be consuming a fair bit of energy as well. Cold temperature -4F performance is in the 2.2 mi/kWh range for me.

 

I didn't know the MINI Cooper SE had resistive battery heaters. Honda put battery heaters in the Clarity Plug-In Hybrids they made for Canada, but those heaters operate only while the car is plugged in. Can the SE's battery heater work when not plugged in?

 

You actually might be right. It's probably just a heat pump with water/glycol and not resistive heaters. I believe the i3 uses a R134a refridgerant and a resistive heater.

Haven't seen any teardown videos of the CATL battery pack either.

 

Thoughtful test and hypothesis. Confirms mine too
Cold temp-> Less power draw from thermal management + More power draw from cabin heating -> better discharge efficiency than EPA when cabin heating is off
Hot temp-> More power draw from thermal management+ More power draw from Cabin cooling-> worse charging efficiency when car is not moving and preconditioning with AC ON

 

@Puppethead how fogged up do your windows get? Mine get very fogged very quickly & I have to run the rear defroster + the windshield defroster fan fairly high, which takes a fairly big toll on my consumption. I'd be comfortable enough with a hat & gloves & no heat but I do kinda need to see, do you have any tricks/recommendations?

 

I can state from experience there is no battery heating system. When I drive home in sub-zero temperatures after the SE has been sitting outside unplugged for the whole day I'll often have 60%-70% (sometimes less, as low as 30%!) e-power and it will not rise at all even after driving ~40 miles.