Trip to Maryland - Cold Weather Driving

CaptDaveHowe · Jan 22, 2015

Took a trip to St. Michaels on the eastern shores of Maryland from Long Island. Stopped first at the Hamilton Marketplace supercharger in NJ, which is 111 miles from home. Began the trip with 200 miles and ended up at Hamilton with 64 miles left. Charged up to 164 miles and left for Newark DE, which is 75 miles away. Arrived with 65 miles left. Charged up to 175 miles and left for St. Michaels and arrived with 72 miles left.

The temperature averaged around the high 20's (26 to 29 F). The loss due to cold weather driving was significant (20 % +). I am figuring that most of this had to do with maintaining the cabin temperature at 68 F. What is thought of the amount of loss due to batteries effected by cold weather? I was surprised as I did not think that 26 - 29 F as being extreme.

DFibRL8R · Jan 22, 2015

I've put about 45,000 miles on my 60kWh in 2 years. My observation is the cold just below freezing temps mainly drive up consumption due to use of cabin heat once the pack is warm (either from preheating/charging right before departure or having warmed up from use). You can test this by turning off the cabin heat and seeing your Wh/mile return to more normal numbers. I suspect in more extreme cold, the battery requires more active heating to maintain a good operating temp.

vdiv · Jan 22, 2015

Can you leave the cabin heat on while the car is charging? Also how fast were you going, with the speed limit? ~20% loss (relative to 70F drving?) does not seem bad at all.

Bighorn · Jan 22, 2015

The battery won't be cold after supercharging or driving any decent distance. All your excess consumption came from using cabin heat and possibly velocity. You can spare yourself some of that expense by getting the car nice and warm while supercharging and also tempering heater use with the seat heaters. Road speed can also make meeting rated miles unrealistic under the best of circumstances.

JohnQ · Jan 22, 2015

Need more context to see if it was only the cold/cabin heat/battery heater. What is your usual highway cruising speed? What was the wind like?

I've driven CT to Newark (186 miles) and, in the same temps you describe, have used anywhere between 210 RM and 240 RM depending on how heavy my foot is and how strong the wind is blowing.

jerry33 · Jan 22, 2015

vdiv said:
Can you leave the cabin heat on while the car is charging?

Sure. Just start the cabin heater with the App. If you had range mode on while driving, turn it off when charging.

CaptDaveHowe · Jan 22, 2015

Thanks for all of the response. Here a few added points.

Preheating: I did charge the car at home overnight and turned the heat on using my iPhone App about 30 minutes prior to leaving while plugged in to my HPWC.
After each stop I also turned the heat on while plugged into a supercharger.
The car cabin was about 69-70 degrees prior to leaving.

Driving: I'm not sure what the wind speed was, but it was a light wind day. I averaged around 70 MPH, not too heavy on the foot.

My friend who is a thermal engineer for Northrup/Grumman said that in his opinion that cars overall do not have a high amount of insulation and at high speeds in cold weather, the energy required to keep the cabin warm is very high. As a Model S uses battery power to heat the cabin, the loss of power is probably attributed to cabin heating.

I think that he correct in his assumption. It really does make you re-calculate long trips in cold weather though.

Saghost · Jan 22, 2015

CaptDaveHowe said:
My friend who is a thermal engineer for Northrup/Grumman said that in his opinion that cars overall do not have a high amount of insulation and at high speeds in cold weather, the energy required to keep the cabin warm is very high. As a Model S uses battery power to heat the cabin, the loss of power is probably attributed to cabin heating.

I'd mostly agree with this.

Tesla threw a joker in the deck with the Model S, though: I've read the heating and cooling systems are interlinked, and the car can heat the cabin with drive motor/inverter waste heat. There isn't enough of this to warm the car fully even when driving, let alone while sitting - but it should reduce the workload of the cabin heater module some and thus reduce the range penalty.

As with any EV, you'll get more range by using the heated seats instead of HVAC where you can.
Walter

DFibRL8R · Jan 22, 2015

Saghost said:
I'd mostly agree with this.

Tesla threw a joker in the deck with the Model S, though: I've read the heating and cooling systems are interlinked, and the car can heat the cabin with drive motor/inverter waste heat. There isn't enough of this to warm the car fully even when driving, let alone while sitting - but it should reduce the workload of the cabin heater module some and thus reduce the range penalty.

Walter

On the flip side, I've noticed in the summer when I drive with the AC set to "off", sometimes it seems to kick on anyway with noticeably cooler air coming from the vents. I figured the pack is getting actively cooled and there is some spillage into the cabin climate cooling system.

Doug_G · Jan 22, 2015

If the car is fully warmed up, then you'll see about 10% range loss at those temperatures. It's mostly due to aerodynamic drag, not the heaters. But if the car is stone cold then you can get massive extra power draw.

For details please see my blog - Cold Weather Driving - Blogs - Tesla Motors Club - Enthusiasts & Owners Forum

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Trip to Maryland - Cold Weather Driving

CaptDaveHowe

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DFibRL8R

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vdiv

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Bighorn

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JohnQ

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jerry33

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