Winter Cold Battery Efficiency

This was directly after driving 40 miles at freeway speeds in 80 degree weather, so the battery was probably pretty toasty and fast charging made it toastier.

 

I have a 63 mile total round trip commute, about 90% at 70 MPH and the rest at 55 MPH. I use standard driving mode with the AC on "auto" at 70 degrees.

In 80 to 90 degree temps, I arrive home with 50% SOC.

This month, in 35 to 50 degree temps, I've been arriving home with 40% SOC.

So, maybe a 10% hit in moderate cold temperature. I could probably mitigate some of that, if I wanted to scrimp on speed and heating, but I really don't need to.

 

63/(1.00 - 0.50) = 126

63/(1.00 - 0.40) = 105

(126 - 105)/126 x 100% = 17%

Still better than most other EVs, though!

 

I continue to be impressed with the heat pump on the SE. I drove the Bolt the other day, and was getting under 2 miles/kWh. The SE is getting 3.5! This is with OAT at 32F and thermostat set to 65F in both cases.

 

You have amazing discipline! I don't know how I've avoided a speeding ticket during the 5 months I've been driving my SE. To the SE's credit, I believe the silent acceleration helps keep the car on the down-low, avoiding the attention of the authorities.

 

There is also the fact that at 23F, roads are often slippery. Do you have snow tires, or the OEM summer tires? I still have only the summer tires, so I won't be pushing the accelerator that hard when temps are below freezing.

In fact, I haven't driven my SE much at all since I got it between working from home and having snow tires on the other car.

 

I'd love to know what happens with the summer tires in deep snow when you nail the accelerator with no hope of achieving traction. Does the anti-wheel-slip logic cause the front wheels to turn slowly, like the second hand on a clock while the car remains stationary?

 

This should be easy enough for me to test. It has been snowing for over 24h here, and I still have the OEM tires on the car. The bigger question is whether it is wise to venture out in it right now.

 

Maybe wait for a less-snowy day. I don't want you to get stranded halfway down your driveway with your Summer tires.

I've been driving front-wheel drive cars in the snow for decades and sometimes in new snow I enjoyed cranking the wheel over and nailing the accelerator to achieve massive understeer. Then I'd slowly back off on the accelerator until the winter tires got traction and jerked the car into the direction they were pointing. The SE won't let me do that anymore. It's strange to have the car instead of me deciding how much the accelerator pedal can affect (or effect?) wheel-spin.

Edit: I decided it's "affect" because the accelerator pedal cannot "effect" wheel-spin in the MINI Cooper SE.

 

I've never tried that particular maneuver in the snow. Normally I get some speed, turn the wheel (not so fast as to understeer) and yank the parking brake. That typically sends the rear axle spinning. I wonder if the Mini would allow the brake to engage in that situation. Probably not.

 

Thanks for the tip. I have lived most of my life in NY, but I have never driven on summer tires in the winter. Before the mini, every car I've owned either had all-seasons (at worst) or better yet had real snow tires in the winter. I was hoping that my car would be delivered in the spring so that I had 6 months to invest in winter tires. Alas, my car came 3 months earlier than promised so now it sits undriven under several inches of snow.

 

I just did a 600-mile road trip in Utah last weekend. I found that the range was around 95-100 miles per charge. This was freeway driving with the cruise control set at around 75-80 mph. I normally get around 120 in Green+ mode in warmer weather. The low end of the range was in an area with elevation changes (climbing). The bulk of the trip was using Electrify America DC chargers. Full charge from 5% to 98% was are an hour.

 

Full charge (to 98%) is an hour, but isn't an 80% charge only 30 minutes? This really highlights how to travel with an EV. Unless you need that full charge for your next leg, it makes much more sense to leave at 80%.

I'd love to hear more details about your trip. How tedious did you find it to be?

I've road tripped in a Chevrolet Bolt which, other than a larger initial range, is similar to the SE. With the Bolt, there is a severe taper around 55%. Below the taper, it charges at similar rates to the SE (about 50kW). I try not to charge above the taper to optimize travel time, leaving me with a charge-to-charge range of about 100 miles.

 

Before reading, a preemptive apology for using formulas and math

The thing to remember about cold driving is not just battery performance/heating use. The air is more dense at lower temps. From simple formulas, PV = nRT which means for the same air pressure and volume, the colder it is, the more air molecules there are. This means air density increases. The power required to overcome air friction is 0.5 . p . Cd . A . v^3, so if all else stays the same, increasing p (rho, or air density) increases the power required. going from (sorry I work in C which makes Kelvin easier) 30C to 0C means you need around 10% more power to overcome air friction. The faster you go, the more that air friction plays a part. It is proportional to v^3, whereas rolling resistance is proportional to v. So, at a fast speed, the majority of power is required to push through the air. Decreasing the temp from 30C (around 87F) to 0C (32F) will increase the power requirements by about 10%, hence 10% lower range. This is before any differences in battery performance.

 

I got my SE in late November, and one of the first things I did was put snow tires on. My brother works for Michelin, and recommended the Michelin Xice XI3 195/55R16 91H XL / (54661). I had them installed at National Tire and Battery, but ever since, I hear a squeaking sound in the cabin, like rubber on plastic. It happens mainly on acceleration from a stop. My wife is convinced it's coming from the front right wheel well, but to my ears it sounds more generalized. I've taken it back to NTB twice and they said the install is fine, no rubbing, but that the sound could be explained with the stronger traction of the snow tires. I'd love any advice on this. (The dealership said it should stop when I switch back to the tires that came with the car originally.)