If you're not getting the Wh/mile efficiency you're expecting...

sdbyrd79

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#1
Make sure you have enough air in your tires :)

For the past 3 months, I've only managed to average around 240 Wh/mi no matter how "normal" my driving habits were. I still thought it was good, but when others were reporting much lower, I was wondering what I was doing wrong. Come to find out, my tire pressure had been routinely around 39/40 psi, when my recommended pressure states 45. I bumped it up to around 44 for all 4 tires and my daily commute went from 240 to around 210 Wh/mi. The only reason I caught it is with lower temperatures in the morning it was dropping to 38 which triggered an alert. That's an improvement of about 15% :)
 

Nikola

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#2
There are a bunch of threads popping up here that are all just variations on the theme: I only got XXX miles range, why did it happen?

Most of the time it's hard to be sure, because range can be GREATLY affected by:
speed​
driving style (lots of hard acceleration, for example)​
aero wheels (a 4-5% range hit without them on the highway, seems to be the consensus)​
altitude changes (climbing or descending, especially mountains but even small changes of 1000 feet or so)​
heating requirement (cabin and battery)​
and yes, tire air pressure​

Anyone who is wondering why they aren't getting the range they expect, should post the factors above and the actual Wh/mile the car recorded for their trip.

For example, we routinely run 100 mile trips on flat roads in Arizona and generally get 220-240 Wh/mile, which will deliver about the rated 310 mile range from a full battery. That's with the cruise set at 78 MPH, with constant air conditioning (which doesn't hit the range nearly as much as heating), aero wheels, non-aggressive acceleration, and tires at 42 psi. Lifetime average is 220 Wh/mile after 11,500 miles, mostly highway.
 

kort677

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#5
in addition to temps, other factors affect your wh/miles. things like rain/snow will cause drag, headwinds cross winds, elevation changes and driver's behavior, doing fast accelerations, stops signs on every corner all take a toll on range.
 

ADK46

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#6
Unless regen kicks in, if you maintain a constant speed and there’s no net change in elevation, there’s no penalty to a hilly route versus a flat route.

This does not seem right, especially if you are a cyclist, but here’s the reason: The distance is the same, so energy going to rolling resistance is the same. The speed is the same, so energy going to aerodynamic resistance is the same (this is why bicycling is a different case - it’s not generally possible to maintain a constant speed). The potential energy of gravity gained going up is returned going down at 100% efficiency (again, not true if regen kicks in).

This analysis ignores varying efficiencies from varying power outputs. It’s not clear which way that might go, but my guess is that it’s not a big factor.
 

ADK46

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#7
More theoretical pondering!

The proverbial jack-rabbit starts in a ICE car are bad for two reasons, only one of which applies to EVs: the indirect hit taken by later braking, regen or otherwise, when braking hard at the next light. I’m talking to you, you boulevard racers!

The other cause comes from operating the ICE in a less efficient regime. But the efficiency of EV inverters and motors improve with output (to a point, but at least up to a 50% output).

I’m not sure I’m considering all the factors involved. Thoughts?
 

babula

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#8
There are a bunch of threads popping up here that are all just variations on the theme: I only got XXX miles range, why did it happen?

Most of the time it's hard to be sure, because range can be GREATLY affected by:
speed​
driving style (lots of hard acceleration, for example)​
aero wheels (a 4-5% range hit without them on the highway, seems to be the consensus)​
altitude changes (climbing or descending, especially mountains but even small changes of 1000 feet or so)​
heating requirement (cabin and battery)​
and yes, tire air pressure​

Anyone who is wondering why they aren't getting the range they expect, should post the factors above and the actual Wh/mile the car recorded for their trip.

For example, we routinely run 100 mile trips on flat roads in Arizona and generally get 220-240 Wh/mile, which will deliver about the rated 310 mile range from a full battery. That's with the cruise set at 78 MPH, with constant air conditioning (which doesn't hit the range nearly as much as heating), aero wheels, non-aggressive acceleration, and tires at 42 psi. Lifetime average is 220 Wh/mile after 11,500 miles, mostly highway.
Location is also a huge factor, I discussed this many times in other threads but worth a mention here as well. Driving in the city, for example Queens NY where I live, the constant stop and go makes it almost impossible to get under ~280 Wh/Mi. Because I have a stop sign or red light practically every block, even if I drive in ideal conditions my Wh/Mi is consistently high.
 

Bigriver

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#9
Outdoor temperature, outdoor temperature, outdoor temperature.
.
Yes, yes, yes. While other posts are mentioning valid factors, the biggest one for me is the outdoor temperature. Not many Model 3’s have experienced their first winter. Just wait until your 300 mile long range version feels more like the 200 mile standard range version. Of course, unless you live somewhere with perpetual warm weather. Attaching a graph of my efficiency as calculated by Teslafi for my Model X, from 5F to 95F.
8d2578e4-d0a1-465e-bd51-16fff77d92f2-jpeg.16264
 

kort677

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#11
Location is also a huge factor, I discussed this many times in other threads but worth a mention here as well. Driving in the city, for example Queens NY where I live, the constant stop and go makes it almost impossible to get under ~280 Wh/Mi. Because I have a stop sign or red light practically every block, even if I drive in ideal conditions my Wh/Mi is consistently high.
that is because the car runs more efficiently when driving at a constant rate of speed, your constant stop start routine, constantly accelerating after each stop hammers your wh/miles. that's just the part of city living that you're stuck with.
 

ADK46

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#12
I am sorry to be the one to bring you this bad news but your analysis is just not correct.
Where is it wrong? I am aware it's conclusions are not what people think, or reflect common assertions, which I suspect are holdovers from ICE cars. Is it contrary to experimental data obtained for the conditions I've specified?
 

Dr. J

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#15
because the amount of regen cannot compensate for the added usage of wh/miles used to accelerate uphills
@ADK46 specifically excluded this in the assumptions: "Unless regen kicks in...." It may or may not be a practical assumption, but it's a theoretical exercise anyway.
 

slasher016

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#17
@ADK46 specifically excluded this in the assumptions: "Unless regen kicks in...." It may or may not be a practical assumption, but it's a theoretical exercise anyway.
It's impossible* to maintain a constant speed downhill WITHOUT regen kicking in. So that's a completely invalid assumption.

* assuming you're not at 95-100% battery
 

ADK46

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#18
It's impossible* to maintain a constant speed downhill WITHOUT regen kicking in. So that's a completely invalid assumption.

* assuming you're not at 95-100% battery
Depends on where you live, how hilly it is, how fast you’re going. I sorta live in the mountains but rarely see green on the Interstate.

But holy smokes, our heavy aerodynamic cars will coast to 100 mph on just a 3.2% grade. Theoretically. So the regen assumption will often fail, true.
 

PNWmisty

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#19
It's impossible* to maintain a constant speed downhill WITHOUT regen kicking in. So that's a completely invalid assumption.

* assuming you're not at 95-100% battery
That's false. A constant speed can be maintained downhill when the slope of the hill is sufficient to make up for the aerodynamic drag and rolling resistance. The faster the constant speed you wish to maintain, the steeper the hill required.

If your assertion were true, then even a 1% grade would be sufficient for a car to accelerate to 150 mph and beyond.
 

PNWmisty

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#20
@ADK46 specifically excluded this in the assumptions: "Unless regen kicks in...." It may or may not be a practical assumption, but it's a theoretical exercise anyway.
Exactly! We need more critical thinking. I've been on many hilly roads that don't require any regen. Also, I've driven miles through roller-coaster type hills without regen although in this case speed varies with the slope.

On another note, I've found the Model 3 to be super efficient in the mountains, even when massive amounts of regen are needed to check speed before hairpins and corners. Part of this is due to the lower aerodynamic drag when barometric pressure is lower (due to altitude). But my observations from careful, real-world use indicates that hilly terrain does not need to have a large impact on efficiency when driven in a sensible manner. This, of course, assumes the starting and ending elevations are the same. Speed, on the other hand, has a huge impact on range. As does a strong headwind or crosswind. As does low tire pressure. Hilly terrain, not so much.