Road Trip Power Usage

[Doug_G]

I recently drove to Montreal and back in my Model S (I've done this many times in the Roadster, but this was my first in the Model S).

Driving out in the afternoon, it was raining steadily. I was getting 245 Wh/km, going right on 100 kph the whole way. That's quite a bit more than normal. Usually you can get Rated Range at around 90-95 kph.

Driving back at night, the rain had stopped but it was a bit cooler. I was getting under 200 Wh/km while going 100 kph. I actually sped up to 110 kph and it still consumed less power than the outbound trip.

In previous trips with the Roadster I found the power consumption was the other way 'round - a little more going westbound than eastbound. Probably due to prevailing winds.

No significant elevation changes. Was only mildly breezy, and since the weather was coming from the West I doubt I was hitting headwinds. Was that ~ 20% energy difference due to the rain? I've not done a whole trip in the rain before, but neither do I recall seeing that much effect.

 

[GSP]

It probably was the rain. Rain means a big hit in EV miles on my Volt, about 25% less. I think it makes sense, since it takes a lot more force to move through 100% water than it does 100% air, especially at 100 kph!

GSP

 

[mknox]

I drive from the GTA to the Waterloo Region and back every day (not as far as Ottawa to Montreal, obviously) and I use a bit over rated on the way out and a bit under on the way back. At the end of the day, my trip usually comes in at just under 300 Wh/mi. I drive between 75 and 80 MPH (120 - 130 km/h) on the 401 (unless you're a cop, then I drive exactly 100 km/h :smile I have not found rain or even heavy a/c use to make any appreciable difference in these numbers. However, when the temperature drops to near or below freezing, like it was last March when I got the car, my energy consumption goes up a LOT.

 

[efusco]

Just for perspective....
245 Wh/km = 394 Wh/mi
200 Wh/km = 322 Wh/mi

And I'll add that that is pretty similar to my experience, the rain really has a dramatic impact on efficiency. I previously posted about an interstate roadway drive that caused my first range anxiety episode and I was feeling a bit at a loss of how to deal with the loss of efficiency even after dropping my speed.

 

[Doug_G]

It wasn't anywhere near cold enough to affect my range. The rain was relentless. It was a steady downpour for the entire trip. When I've encountered rain before it's been intermittent and it didn't have anything like that effect.

I did notice a reduction in power consumption when the road turned to concrete. I think there must have been standing water on the road, as opposed to it just being wet.

 

[Zextraterrestrial]

road surface makes a huge difference too. We have a corridor that is getting repaved and the old opengrade HMA vs the fresh dense grade is like night and day, sound and energy usage. maybe 10%? I need to drive it in my S more and see what it is like now compared to my year worth of data

 

[wycolo]

Bottom Line: You got home with a lot more 'battery' left over compared to the Roadster, right??
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[brianman]

I need to drive ... in my S more

Always true.

 

[Doug_G]

Bottom Line: You got home with a lot more 'battery' left over compared to the Roadster, right??
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This time, yes, but that is not always the case. If you do a trip where you need to charge en route, you find the Model S takes longer to charge on a range basis. That's because it takes more energy per mile. So on a long trip, lacking superchargers, it is often faster to take the Roadster.

 

[Jaff]

(and more fun...:biggrin::wink: )

This time, yes, but that is not always the case. If you do a trip where you need to charge en route, you find the Model S takes longer to charge on a range basis. That's because it takes more energy per mile. So on a long trip, lacking superchargers, it is often faster to take the Roadster.

 

[mknox]

It wasn't anywhere near cold enough to affect my range. The rain was relentless. It was a steady downpour for the entire trip. When I've encountered rain before it's been intermittent and it didn't have anything like that effect.

I drove from Hamilton to Brampton in a relentless downpour about a month ago. It was the one and only time I've gotten a TPMS Error message and I'm guessing that all the water caused RF interference between the wheel(s) and the car. Again, not a huge long drive, but my energy consumption was not really affected by any great amount. It might have been offset by the fact I was driving slower than I normally would have due to the rain.

Having said that, anything that affects rolling resistance should impact energy consumption, and it would be amplified by a longer drive. There are some highways around here that have some sort of water channelling that is supposed to help with the spray kicked up by other vehicles (and it does work). I wonder if that helps with range since standing water is being channeled away?

 

[brianman]

This time, yes, but that is not always the case. If you do a trip where you need to charge en route, you find the Model S takes longer to charge on a range basis. That's because it takes more energy per mile. So on a long trip, lacking superchargers, it is often faster to take the Roadster.

This is an aerodynamics/weight thing, right?

I'm curious what this might mean for a Model-S-battery-tech-in-first-gen and next-gen roadsters in terms of time-efficiency while travelling.

 

[Doug_G]

This is an aerodynamics/weight thing, right?

Right, much smaller vehicle. The Roadster takes perhaps 2/3 of the energy of the Model S. As a result it effectively charges 50% faster. 60 kph charging in the Model S is equivalent to 90 kph charging in the Roadster. That makes a huge difference in the waiting time on a road trip, and therefore a huge difference in the overall trip time. That's despite the fact that you inherently start with more range in the Model S.

On the other hand, the Model S's heating system is far more sophisticated. From what I can tell, it uses the battery/drive train as a reservoir for the heat pump, essentially using waste heat to help warm the cabin. Once the car is warmed up the power draw of the cabin heater in the Model S is much lower than that of the Roadster at the same ambient temperature. For a winter road trip I have to turn off the heat in the Roadster and just use the seat heaters - after several hours I'm pretty chilled even wearing long johns! In comparison I stay nice and toasty in the Model S with minimal impact on range.

I'm curious what this might mean for a Model-S-battery-tech-in-first-gen and next-gen roadsters in terms of time-efficiency while travelling.

I expect you'd get Roadster-level efficiency with Model S-level range - a very nice combination. If Tesla comes out with a Roadster upgrade pack containing Model S cells we'll already be there, I suspect. Except for the improved heating system.

 

[wycolo]

Trip to Big City 150 miles away (with only 30A 203V EVSEs available):

MS: Charge to max = 270 miles. On arrival = 120 remaining, so need to charge 30 miles.

R: Charge to max = 235 miles. On arrival = 85 remaining, so need to charge 65 miles.

If as you say, R charges 50% faster then it comes out even. I'm just hoping the new ChargePoint (next to the new ChaDeMo) will do better than 203x30.
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