Wh/mi rate at startup -- calculation or consumption?

[RubinRA]

When I begin driving my Model 3, the display shows very high power use in Wh/mi -- typically in the range of 500 or so. Once I've been driving for a few minutes, it settles down to a more acceptable rate, under 300 (and under 250 if I'm not at freeway speeds). My question: is that initial figure reflecting actual power consumption, or a result of the computer not having enough data on the trip to calculate accurately? If the former, why would consumption be so high at the beginning of a trip?

 

[Zoomit]

The former. Initial consumption can be high due to the initial heating or cooling needs for the cabin or battery. Each of those can peak around 7 kW. If it’s just a few minutes, it’s more likely cabin climate control.

 

[jmaddr]

Take a look at your energy bar graph right below the speedometer right when you get in. Just like when you're driving, it's in the black range a little bit if the AC is blowing heavily. This shows how much energy the car is using...standing still...cooling down the cabin.
I've turned on pre-cool a little too early before and when I got in and took off, the Whr/mi was above 3000! It came down after a few miles, but you can see how much impact climate control can have on short trips. On longer trips, climate control becomes less of an issue.

 

[camalaio]

It's kind of both.

The number is very real, and the same thing happens for ICE vehicles. When you first start moving, it requires a lot of power to accelerate. If you look at just the energy during acceleration time, it will indeed be a lot! But as you maintain speed, the energy required to accelerate gets overshadowed by how much energy it takes to maintain that speed.

 

[electrongeek]

I think a portion of that initial high consumption is related to cold tires and higher rolling resistance. As you drive, the rubber will get a bit warmer and more flexible, resulting in lower rolling resistance and contribute to a lower Wh/mile figure.

 

[camalaio]

I think a portion of that initial high consumption is related to cold tires and higher rolling resistance. As you drive, the rubber will get a bit warmer and more flexible, resulting in lower rolling resistance and contribute to a lower Wh/mile figure.

More flexibility would mean greater rolling resistance. But warmer tires result in higher pressure and less flexibility as a result, which does help for rolling resistance. This would be hard to notice though, certainly not anywhere near as apparent as the OP's points.

 

[Tdriver]

Call up the energy graph and set it for the 5 mile scale. Then check the left side and right side readouts to see whats going on.

 

[Zoomit]

More flexibility would mean greater rolling resistance. But warmer tires result in higher pressure and less flexibility as a result, which does help for rolling resistance. This would be hard to notice though, certainly not anywhere near as apparent as the OP's points.

The higher pressure reduces rolling resistance but higher temperature reduces energy dissipation by the elastomers which also contributes to lower rolling resistance, at least according to this Michelin slide package (page 86).

It appears the effects are about equal. According to the graphs in those slides, the increased pressure (~6 psi) of a fully warmed tire reduces Crr by about 10% while the higher temperature (~50 F) reduces Crr by another 10% or so.

 

[jdcollins5]

Think about it. It is Wh divided by miles. It updates every 0.1 miles. The first few updates are due to low bottom number. After you drive enough to get larger bottom number then the Wh/m number becomes more reasonable.

Also if it is cold or hot, you are using more heat or AC to heat or cool cabin when you start.