Winter Cold Battery Efficiency

I have XI3's on my other car, and haven't had any issues with them there. They are certainly louder than the summer tires, but there is no squeaking. Of course, being a different car, it's apples and oranges. I still have summer tires on my SE, so it is stationary more often than not these days

 

The 16" XI3's on my SE don't make that exact sound. Besides the whine you'd expect from Winter tires, they do make a "swish" sound when I accelerate briskly that my impressively quiet Hankook Summer tires don't make, but I'm sure that sound is coming from both front tires. It's nothing like a rubbing sound. Without an engine making noise, I hear a lot of sounds from my SE and from outside my SE I wouldn't otherwise hear.

 

That's pretty awesome.

I even drop to 70% sometimes - it's been regularly about 10 or 20 above here. A hint I found is to not start charging immediately overnight but set it to start a few hours before leaving. That seems to keep me at 90-100% though really I don't need more than 30% in town driving and 50% if doing an on ramp. The top 50% is just for fun.

To toss out my info so far. It's been mostly 10-20 degree driving (most of the time I can avoid sub 0 temps due to my life though cannot next week) I have been averaging guessing 100 miles. 3.3mi/kWh so far average. All freezing or below.

 

That was a great test!

 

After today's drive in 5ºF with a wind chill warning:

• Car was climatized for 15 minutes while plugged in to level 2 charger in my "heated" (34ºF) garage.
• Climate controls during the drive were set at 67ºF driver/65ºF passenger, but I only turned the fan on as needed to defog windows. My wife and I were both really bundled up due to the -11ºF wind chill, so the cabin felt plenty warm after the climatization.
• 16 of those 29 miles were at interstate speeds (65-70mph). The rest were on city streets (~40mph).
• Car was parked for about 10 minutes outside halfway through the journey, so not much time for cold soak.
• I did not see a reduction on the E-Power gauge at any point.

 

I'd love to know the formula MINI uses to determine how many E-Power bars to disable. This week I've been missing 4 or 5 bars every day this week and it hasn't been colder than 14 degrees F. However, our MINI doesn't get to hang out in a steaming hot 34-degree garage.

 

I'm curious about this as well, which is why I shared my experience to add another data point. I suspect I would have seen reduced power if my car was outside long enough to cold soak.

I doubt BMW/MINI would ever publish the formula/conditions. We likely need to find an app that shows the detailed stats of the battery packs to really figure it out. I know those apps exist for Teslas and Leafs...

 

That is accurate for heat pumps in general. With home based units you have the option to add pan heaters to the outdoor unit to extend the temps they can run at, but you don’t have that option in an EV since they will pull power from the battery.


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Cold soaking seems to be an issue with it. I will say, I am garaged, but my garage hasn't been above freezing for quite a few weeks now. I don't always drive often far enough to jump back up to 100% either. I really am not minding as I don't need it and especially in the cold I shouldn't zip along as fast with icy spots. However charging just before leaving does help a lot. This is only a 3 month issue really here so I am sure I'll be okay. I know someone with a Bolt and once in a while they get a reduced propulsion message or something. Said they don't know until more severe reduction happens - cannot confirm that though.

 

I have a Bolt and an SE. The SE reduces power for me all the time in the cold. I have never seen the Bolt reduce propulsion due to cold, only low state of charge. Both cars are treated the same, parked next to each other outside.


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You missed my point I think. The Bolt does take a hit in the cold per the owner in same conditions. In fact given temps I've driven the Bolt was worse on when it was really reduced. But that could be dumb luck. I don't recall them saying they saw easily when power was reduced unless they got the message.

Here's a thread with someone talking about the cold and that message too.
https://www.reddit.com/r/BoltEV/comments/amaggq/bolt_2019_extreme_cold_weather_stress_test/

BEVs just don't love the cold. No big deal to me as all hate it.

 

My point really is just that the SE is much more sensitive. Cold soaking the Bolt overnight in sub-zero Fahrenheit temps has never given me reduced propulsion, only reduced regen. Meanwhile, cold soaking the SE at 20F overnight does reduce propulsion.


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Nah still missed it. The owner felt that they are getting a reduction but aren't told until it hits a lower threshold where it would be noticeable hence the warning. I personally wouldn't notice on my SE unless I was below 30 or 40% really when it's super cold out.

 

Ok. I just figured you were focused on the temperature aspect since that is the topic of this thread.

Well I’ve only seen reduced propulsion at very low SoC (below 10% or so). You are right that, unlike the SE, the Bolt doesn’t tell you how much it has been reduced. Out of curiosity, I goosed it to see what I could get. In this case, I still got about 130kW. The car normally can give 150kW or so, so it wasn’t reduced by that much.

This is just one data point. I have no idea how much the car reduces power in different situations. And it doesn’t tell you either.


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Yeah sorry I wasn't making it clear enough at first. Totally on me. I had done a ton of reading about the cold and asking the owners of others what they see and get. Since I got mine we've been comparing and that was one thing they couldn't compare 100% since they didn't have access to it. Only when that propulsion warning comes up can they have a clue.

Maybe if Mini got rid of it we'd be clueless too? I have no idea. I do know cold soaking sucks for batteries. We're in for snow this week so I'll be sidelined I think in my car. Pity too because if will be super cold as well to try to get data points but I likely won't be able to leave my driveway. Kind of bummed as I do want to see how this handles snow with the traction control at different levels.