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Best Stopping Mode for Motorway Driving?

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50% of my driving in my Model 3 is on motorways, very early in the morning. As such, there's rarely any other traffic around, and I'm very rarely called upon to use the brake (in any car I've driven). It's 30 miles of nonstop, constant, 70mph.

This got me thinking. Since I picked up my M3 at the weekend, I've been using Hold mode for the one-pedal driving experience, and I really like it - although it takes some getting used to to avoid braking prematurely and leaving a huge gap between you and the car ahead/the junction.

I know it's good for energy regeneration, but here's my question - is it best for nonstop 70mph driving, or would it actually be more economical to be in Roll mode, and let physics carry me forwards?

My thinking is:

Hold Mode: I need to apply a constant pressure to the accelerator, meaning I'm always using energy to keep me at that constant speed.

Roll: I'd intermittently apply the accelerator, but there would be many instances whereby I'm not accelerating, and just rolling. This should (I think?) be using zero energy.

Anyone have any thoughts?
 
I mean use TACC/AP if its that quiet (although I still hover over the accelerator in case of sudden braking).

I think both modes work the same until low speed so stop/start traffic and congestion in towns is perhaps the only time you'd notice the difference. You'll still need to balance the throttle to maintain your speed at 70. And only using as much energy as needed - eg going downhill you'll be using no energy or even slight regen and vice versa.

for traffic lights etc I use creep mode - you can kick in hold by pressing firmly on the brakes so I do that at traffic lights while creep lets me slow to a crawl and roll up for fine tuning position behind traffic.
 
Hold Mode: I need to apply a constant pressure to the accelerator, meaning I'm always using energy to keep me at that constant speed.
At 70 mph you need quite a bit of power to maintain speed due to air resistance - come off the throttle in an ICE vehicle and you will slow down reasonably quickly. Even on a decline you would only reduce power rather than come off the throttle completely so there really won't be a time when you would be rolling.

Certainly give it a go though, some people's driving style may benefit - certainly I know some people that are constantly on/off the throttle even when maintaining a constant speed so they would benefit.

The other advantage is you can come off the throttle to reposition your foot/stretch your leg briefly without braking.
 
Do a musk - work it out from first principals. You need a given amout of energy to get you from A -> B. Applying this constantly or in pluses should average out to the same. All the hypermiling stuff in ICE is to work around it throwing power down the exhaust or into the brakes. All the old hypermiling rules kind of go out the window on an EV where regen captures any excess energy.

Keep an eye on either the energy graph or the green line above the speedo to see what you are actually spending, but generally staying contant will probably work out slightly better. If you really want to fineness things, avoid accelerating up hill so you aren't accelerating against gravity, but accept its gift down hill instead.

TBH you would probably see more overall energy saving from driving 5mph slower than you will from trying to trick the system. AP and enjoy the ride - being able to relax more on a motorway has made a huge difference for me in terms of enabling more travel around a working day when needed.
 
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Or take a more pragmatic view - 30 miles @ 70mph - 25 mins 43 seconds or a whole 4 mins 17 secs faster than @ 30mph 60mph which will save a shed load more power than any fancy brake changes @ 70 mph
 
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50% of my driving in my Model 3 is on motorways, very early in the morning. As such, there's rarely any other traffic around, and I'm very rarely called upon to use the brake (in any car I've driven). It's 30 miles of nonstop, constant, 70mph.

This got me thinking. Since I picked up my M3 at the weekend, I've been using Hold mode for the one-pedal driving experience, and I really like it - although it takes some getting used to to avoid braking prematurely and leaving a huge gap between you and the car ahead/the junction.

I know it's good for energy regeneration, but here's my question - is it best for nonstop 70mph driving, or would it actually be more economical to be in Roll mode, and let physics carry me forwards?

My thinking is:

Hold Mode: I need to apply a constant pressure to the accelerator, meaning I'm always using energy to keep me at that constant speed.

Roll: I'd intermittently apply the accelerator, but there would be many instances whereby I'm not accelerating, and just rolling. This should (I think?) be using zero energy.

Anyone have any thoughts?
You will soon become a one pedal driving Ninja! Regen whilst driving along a motorway is exactly the same whether you are in Hold mode or Roll mode ... those modes only kick in at about 3 mph.
 
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Don't confuse the stopping mode with what's actually going on. 'Having to hold your foot in one position' isn't using more energy.

F = ma, Newton's second law, is all this comes down to. To accelerate the car against the various forces trying to resist that acceleration, you need to add force, via the motor's (or motors') torque, the gearbox and wheels (all of which have their own losses). Once you're happy with your speed, you stop accelerating to the point where the force from the wheels' torque on the road equals the forces holding you back. That's it.

The drivetrain isn't 100% efficient, and the efficiency for regen is lower than the motoring efficiency, so speeding up and slowing down is overall less efficient than maintaining a constant speed.

The biggy here is that one of the main forces slowing you down is air resistance, and this is a function of the square of the speed. Driving at 60 creates 4x more drag than driving at 30. This means that driving at 80, rather than 70, creates 31% more drag, so it's worth slowing down.
 
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Don't confuse the stopping mode with what's actually going on. 'Having to hold your foot in one position' isn't using more energy.

F = ma, Newton's second law, is all this comes down to. To accelerate the car against the various forces trying to resist that acceleration, you need to add force, via the motor's (or motors') torque, the gearbox and wheels (all of which have their own losses). Once you're happy with your speed, you stop accelerating to the point where the force from the wheels' torque on the road equals the forces holding you back. That's it.

The drivetrain isn't 100% efficient, and the efficiency for regen is lower than the motoring efficiency, so speeding up and slowing down is overall less efficient than maintaining a constant speed.

The biggy here is that one of the main forces slowing you down is air resistance, and this is a function of the square of the speed. Driving at 60 creates 4x more drag than driving at 30. This means that driving at 80, rather than 70, creates 31% more drag, so it's worth slowing down.
This is extremely interesting, thanks for the explanation. It makes sense that driving more slowly results in less air resistance, which in turn increases efficiency, alongside the duration of the journey. As pgkevet mentions above, the journey duration difference between 60mph and 70mph isn't too great. The beauty of this car is I can easily spend one week commuting at 70mph, and then the next commuting at 60mph, and have tonnes of data to use to work out the cost savings.
 
This is extremely interesting, thanks for the explanation. It makes sense that driving more slowly results in less air resistance, which in turn increases efficiency, alongside the duration of the journey. As pgkevet mentions above, the journey duration difference between 60mph and 70mph isn't too great. The beauty of this car is I can easily spend one week commuting at 70mph, and then the next commuting at 60mph, and have tonnes of data to use to work out the cost savings.
Don't forget to include the value of your time spent sorting out the pennies saved 😉
 
Oh, is regen exactly the same on a motorway? So If I was in roll mode at 70mph, and took my foot off the accelerator, the car would slow down as quickly as it does in Hold mode?

Yes regen is the same. The final stop when using regen in slow traffic feels stronger because the speed of the car is slower. The roll mode automatically stops the regen just before the final stop of the car ... so forces you to dab the brakes. There is no difference in regen strength at normal speeds.
 
Something to bear in mind in one pedal driving, during an emergency stop the millisecond you take your foot off the accelerator to move to the break pedal you are already breaking before your foot actually applies the brake pedal. I would estimate this gives you quite a few yards gained stopping distance at any speed which could easily save you a tidy sum.
 
This is extremely interesting, thanks for the explanation. It makes sense that driving more slowly results in less air resistance, which in turn increases efficiency, alongside the duration of the journey. As pgkevet mentions above, the journey duration difference between 60mph and 70mph isn't too great. The beauty of this car is I can easily spend one week commuting at 70mph, and then the next commuting at 60mph, and have tonnes of data to use to work out the cost savings.
Slower will use less battery, but the question would be whether that really offers you a benefit worth the extra time. For example on a longer journey where you would need to charge it's never a quicker journey do drive more slowly and spend less time at chargers.
 
I prefer hold mode - as others say you get used to it and can eventually judge the stopping perfectly (until regain decides to be unavailable in the cold :))

Whatever mode you prefer - I would really recommend you stick to just using the one mode - and don't change between them - all it takes is a momentary lapse of remembering that you have hold off, and your in a world of pain!
 
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I had to drive from home to Heathrow T5 and back today, in appalling weather in the C43, a 3.0L ICE so the drive was slow, averaging 43mph. I averaged 36.4 mpg, amazing when driving locally it averages about 20mpg. Wearing my ICE hat I wouldn't care, because fuel is everywhere.

Tomorrow I have to drive to Huntingdon and back in the Tesla, 340 miles round trip, in what is likely to be much the same weather. I'll charge to 100% and pre-condition battery and car before leaving at 6.00. It will be interesting to see just how efficient the EV is at what will be a lower average speed. I'm beginning to believe that keeping between 65 and 70 on Motorways is best for range, but it is a tad tedious. OK in bad weather here concentration is needed, but in good conditions the temptation to have fun, either speed or silly acceleration, is so tempting....
 
It's already as efficient as it can be. Look at the power bar - if it's not showing anything then you're free-wheeling anyway. Steeper descent will result in regen to maintain the speed.

Don't overthink it. Also, the modes you describe are low speed anyway.