Impact of cruising speed on range

[EVowner]

1. Cruise control maintains constant speed, so never regenerates power when letting foot off accelerator. Regeneration is crazy helpful. I see it daily when commuting in/out of NYC to work. I actually regain some battery used into work by way if not using cruise rather using my own foot on accelerator and brake pedals.

2. All electronic options consume battery power to operate. Not using cruise control on motorway transit is one less drain on battery.

I am honestly not sure about both of these. Last year I attended Porsche e-school driving event where there were several Porsche engineers with whole event being only about Taycans and Macans. I specifically asked during one of the technical workshops about auto recuperation as I seen conflicting information about when it is beneficial to activate. Engineer confirmed that while the option is there they don't believe that it is good idea to have it enabled on highway or drives with constant speeds as it is more efficient for car to keep rolling than to being constantly slowing down by recuperation and then speeding up again which will always have some energy loses. This function is in their words there for city traffic or if car is going for prolonged period downhill.

I tried doing multiple highway drives with it on and off and honestly I have not noticed any significant difference in consumption. But then again like I mentioned my car seems to giving me random numbers on consumption and its scheduled for check.

Regarding cruise control, while you are technically right I don't think there is much difference in consumption at least not directly. Car unless you manually deactivate every security feature is already checking for obstacles in front of it, centering the car in lane and is also reading speed signs even without cruise control being activated. I am guessing there might be higher pool rate of all these sensors when cruise control is engaged, but I would imagine that would be a small difference in energy consumption. But yeah if you want to conserve as much energy you can turn off even things like ambient lighting, HUD, passenger display or even audio (I noticed that Bose app has even power saving QE preset) or analogue clock. From my experience all this has negligible impact on range/consumption. And yes I have experimented with all these in order to figure out what is happening with my car.

Now with all that said I believe that difference that you are seeing in consumption with cruise control on/off is mainly down to traffic that you encounter. While car lets driver set distance to the car in front of it I noticed that it probably as a security measure is quite cautious and starts gradually slowing down before human would. What is also not clear to me is whether cruise control is also for initial portion of slowing down using recuperation or for security reasons it always goes for normal breaking. This was never clear to me even in my ICE cars with adaptive cruise control. Seasoned driver will just take their foot of the gas and will not hit breaks every time when there is something in front of him if there is enough distance. Yet since car has no contextual data, like if it is in the moment going downhill or uphill, therefore cannot with 100% certainty be always sure how fast it will start slowing down just by releasing gas I would expect it always going for breaks. Either way since I am paying attention to the road I tend to change lane even before cruise control starts slowing down which is also the reason why I am able to have rather constant speed.

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[Yves]

So downhill? Elevation change has a big impact.

The trip going there was identical in regards to average consumption … there is not much uphill / downhill highest point on the trip is 1200 but we do not stay there so it is just on the way …
it’s more of a 1000km with 900 km being rather flat so no it has nothing todo with elevation

 

[TomekGnomek]

I am honestly not sure about both of these. Last year I attended Porsche e-school driving event where there were several Porsche engineers with whole event being only about Taycans and Macans. I specifically asked during one of the technical workshops about auto recuperation as I seen conflicting information about when it is beneficial to activate. Engineer confirmed that while the option is there they don't believe that it is good idea to have it enabled on highway or drives with constant speeds as it is more efficient for car to keep rolling than to being constantly slowing down by recuperation and then speeding up again which will always have some energy loses. This function is in their words there for city traffic or if car is going for prolonged period downhill.

This is exactly why on Taycan you can set it to auto which is the best option.
Not sure why they forgot about it in Macan.

 

[dbsb3233]

I am honestly not sure about both of these. Last year I attended Porsche e-school driving event where there were several Porsche engineers with whole event being only about Taycans and Macans. I specifically asked during one of the technical workshops about auto recuperation as I seen conflicting information about when it is beneficial to activate. Engineer confirmed that while the option is there they don't believe that it is good idea to have it enabled on highway or drives with constant speeds as it is more efficient for car to keep rolling than to being constantly slowing down by recuperation and then speeding up again which will always have some energy loses. This function is in their words there for city traffic or if car is going for prolonged period downhill.

The only scenario that makes sense to me that would make it more efficient to turn regen off during highway cruising is if you're driving on a mostly level highway with lots of short rolling dips.

If the road is flat where you never have to slow the car down from coasting speed, it should always be applying positive power (no regen used).

If the road has long downhill stretches steep enough that coasting speeds the car up too much, you're gonna need to slow it down (regen).

But through a stretch with short dips, coasting down into those dips will only speed the car up a few MPH before it climbs out of the dip, so we don't feel the need to slow it down over such a short dip. It's probably more efficient to just let it coast for those few seconds and let it correct itself on the up-side of the dip than it is to quickly apply regen on the down-side then more power on the up-side.

 

[USMA81]

We can put this to rest pretty quickly: using as little regenerative braking as possible (by not using the manual brake pedal or the not having regenerative setting “on”) is the most efficient way to drive (ignoring a few other factors, such as the impact of speed or drafting). Regenerative braking does not recuperate 100% of the change in kinetic energy. So if you accelerate to 60 miles per hour, and then brake to 50, it is less efficient than driving at a more constant speed and not using recuperative braking. Take that to the illogical extreme (but still relevant): go do repetitive hard accelerations and then hard braking for a couple of miles and measure the drop in battery percentage; compare that to driving the same distance at a constant, even high, speed.

There may be many, other reasons to use recuperative braking, but max efficiency is not one of them.

I recall in the 70’s a trucker in Colorado claimed his truck was more fuel efficient at 70 miles per hour than 60. A news organization put his claim to test and debunked it.

 

[EVowner]

Yeah I see it the same way auto regen has very limited usage. What many Macan owners does not seem to realize is that first few centimeters of brake pedal is actually manual regen. Brakes are used only under more heavy breaking.

That all said I still have no idea if innodrive uses this manual regen or if it always uses brakes. I know Mercedes is bragging about using regen with their predictive cruise control, so based on fact that Porsche says nothing about this my guess is no regen with innodrive...

 

[dbsb3233]

We can put this to rest pretty quickly: using as little regenerative braking as possible (by not using the manual brake pedal or the not having regenerative setting “on”) is the most efficient way to drive (ignoring a few other factors, such as the impact of speed or drafting). Regenerative braking does not recuperate 100% of the change in kinetic energy. So if you accelerate to 60 miles per hour, and then brake to 50, it is less efficient than driving at a more constant speed and not using recuperative braking. Take that to the illogical extreme (but still relevant): go do repetitive hard accelerations and then hard braking for a couple of miles and measure the drop in battery percentage; compare that to driving the same distance at a constant, even high, speed.

There may be many, other reasons to use recuperative braking, but max efficiency is not one of them.

I recall in the 70’s a trucker in Colorado claimed his truck was more fuel efficient at 70 miles per hour than 60. A news organization put his claim to test and debunked it.

Perhaps, but the real point is that using applied slowing of ANY kind is less efficient than coasting. Friction braking recovers 0% and is thus WAY worse then regen. Regen isn't quite 100% but it's way better than 0%. While pure coasting loses no energy.

The question is how much can one avoid slowing the car down? When you need to, regen is far better than friction braking.

I don't think there's many situations where people can reasonably avoid slowing the car down, unless they don't care about the car speeding up to 10, 20, 30 MPH above the speed limit on downhill stretches. That's why I said it's pretty much just driving thru undulating, rolling hills. That's about the only situation I can think of where I'm OK letting the car gain speed going downhill without slowing it down, since it's such a short drop that it only gains a few MPH before gravity slows it down on the upside of the dip.

In most cases this is all moot anyway since we're typically using cruise control on road trips, which is slowing the car down on it's own.

 

[jwatte]

1. Cruise control maintains constant speed, so never regenerates power when letting foot off accelerator. Regeneration is crazy helpful. I see it daily when commuting in/out of NYC to work. I actually regain some battery used into work by way if not using cruise rather using my own foot on accelerator and brake pedals.​

​

2. All electronic options consume battery power to operate. Not using cruise control on motorway transit is one less drain on battery.​

Neither of these is a true statement.

First, the cruise control is adaptive, so it will speed up and slow down based on the car in front of you, so there will be some slow-downs. AND! Repeated slow-down and acceleration is not "better" than a constant speed -- for traveling a certain distance, repeated acceleration and recovery is worse than a constant average speed, because there are always some losses (heat) in both acceleration and slowing down. The one thing that helps with charge/range, is driving slower overall.

Second, the computer and front-facing radar are always on in this car; whether the computation and pulses they emit on the car informatics network are "no change" or "set acceleration to X" doesn't matter at all to battery power draw. Note that the automatic emergency braking is required by law in Europe and I don't think it's defeatable in the US (which is a good thing) and that uses the same radar as the speed-sensitive cruise control uses.

 

[dbsb3233]

Yeah I see it the same way auto regen has very limited usage. What many Macan owners does not seem to realize is that first few centimeters of brake pedal is actually manual regen. Brakes are used only under more heavy breaking.

That all said I still have no idea if innodrive uses this manual regen or if it always uses brakes. I know Mercedes is bragging about using regen with their predictive cruise control, so based on fact that Porsche says nothing about this my guess is no regen with innodrive...

Right, the car is using regen to slow the car down whether hitting the brake pedal (up to the point that regen max's out, beyond which friction braking adds on) or lifting off the accelerator pedal with Regen on. Just 2 different ways for the driver to do the same thing. It's a personal preference by the driver whether they like the lift-up action to slow the car or not.

Many EV drivers (like myself) love that pedal method, but some don't.

 

[dbsb3233]

1. Cruise control maintains constant speed, so never regenerates power when letting foot off accelerator. Regeneration is crazy helpful. I see it daily when commuting in/out of NYC to work. I actually regain some battery used into work by way if not using cruise rather using my own foot on accelerator and brake pedals.​

​

2. All electronic options consume battery power to operate. Not using cruise control on motorway transit is one less drain on battery.​

Neither of these is a true statement.

First, the cruise control is adaptive, so it will speed up and slow down based on the car in front of you, so there will be some slow-downs. AND! Repeated slow-down and acceleration is not "better" than a constant speed -- for traveling a certain distance, repeated acceleration and recovery is worse than a constant average speed, because there are always some losses (heat) in both acceleration and slowing down. The one thing that helps with charge/range, is driving slower overall.

Second, the computer and front-facing radar are always on in this car; whether the computation and pulses they emit on the car informatics network are "no change" or "set acceleration to X" doesn't matter at all to battery power draw. Note that the automatic emergency braking is required by law in Europe and I don't think it's defeatable in the US (which is a good thing) and that uses the same radar as the speed-sensitive cruise control uses.

Yep. For example, when we hit a steep downhill stretch with ACC on, we can see the power meter go negative (i.e. capture power through regen) as ACC keeps the car from speeding up. We're not even touching the pedals.

It would technically be a bit more efficient to just let the car coast, but then we'd be up to 130 MPH and blow through a curve a mile down the steep descent. Efficiency takes a back seat to not flying off the side of the mountain.

 

[pdealessandrini1930]

Yep. For example, when we hit a steep downhill stretch with ACC on, we can see the power meter go negative (i.e. capture power through regen) as ACC keeps the car from speeding up. We're not even touching the pedals.

It would technically be a bit more efficient to just let the car coast, but then we'd be up to 130 MPH and blow through a curve a mile down the steep descent. Efficiency takes a back seat to not flying off the side of the mountain.

Many good experiences and observations.

I suppose we follow whichever practices we deem work best for our driving style.

Yes. Gas our battery, coasting is a great way to extend range.

I’ve consciously tried cruise control on and off.

Totally agree hard acceleration and braking,
Whether gas/ICE or battery isn’t efficient.

In my case commuting to / from NYC in daily rush hour traffic - avoiding hard accelerations or braking without cruise - has improved my range.

I drive 25 miles each way. If I do not use cruise control when I get back in my car at work to go home and next morning to go back to work, my residual battery SOC is higher. It shows higher SOC than the actual math of prior SOC - less - 25 mile one way commute should show.

May not work for others but with 20k miles of commutes and highway weekend driving that’s my empirical experience.

Feathering the throttle matters though. A lead foot is worse than cruise control in my case.

 

[W1NGE]

I am honestly not sure about both of these. Last year I attended Porsche e-school driving event where there were several Porsche engineers with whole event being only about Taycans and Macans. I specifically asked during one of the technical workshops about auto recuperation as I seen conflicting information about when it is beneficial to activate. Engineer confirmed that while the option is there they don't believe that it is good idea to have it enabled on highway or drives with constant speeds as it is more efficient for car to keep rolling than to being constantly slowing down by recuperation and then speeding up again which will always have some energy loses. This function is in their words there for city traffic or if car is going for prolonged period downhill.

I tried doing multiple highway drives with it on and off and honestly I have not noticed any significant difference in consumption. But then again like I mentioned my car seems to giving me random numbers on consumption and its scheduled for check.

Regarding cruise control, while you are technically right I don't think there is much difference in consumption at least not directly. Car unless you manually deactivate every security feature is already checking for obstacles in front of it, centering the car in lane and is also reading speed signs even without cruise control being activated. I am guessing there might be higher pool rate of all these sensors when cruise control is engaged, but I would imagine that would be a small difference in energy consumption. But yeah if you want to conserve as much energy you can turn off even things like ambient lighting, HUD, passenger display or even audio (I noticed that Bose app has even power saving QE preset) or analogue clock. From my experience all this has negligible impact on range/consumption. And yes I have experimented with all these in order to figure out what is happening with my car.

Now with all that said I believe that difference that you are seeing in consumption with cruise control on/off is mainly down to traffic that you encounter. While car lets driver set distance to the car in front of it I noticed that it probably as a security measure is quite cautious and starts gradually slowing down before human would. What is also not clear to me is whether cruise control is also for initial portion of slowing down using recuperation or for security reasons it always goes for normal breaking. This was never clear to me even in my ICE cars with adaptive cruise control. Seasoned driver will just take their foot of the gas and will not hit breaks every time when there is something in front of him if there is enough distance. Yet since car has no contextual data, like if it is in the moment going downhill or uphill, therefore cannot with 100% certainty be always sure how fast it will start slowing down just by releasing gas I would expect it always going for breaks. Either way since I am paying attention to the road I tend to change lane even before cruise control starts slowing down which is also the reason why I am able to have rather constant speed.

All non-drive elements of the car except the heater rely on 12v source so little or no impact on HV battery therefore range. Of course it will be topped up by the HV but I think not really material to the cruising exercise.

Regen / recoup will provide most if not all of the braking to maintain constant speed down to zero - this was the experience in my Taycans.

Motorway driving at a constant speed is the worst environment for range typically and to rely on cruise is probably not ideal either as you have no opportunity to 'coast' from what I understand.

 

[dbsb3233]

Motorway driving at a constant speed is the worst environment for range typically and to rely on cruise is probably not ideal either as you have no opportunity to 'coast' from what I understand.

I don't think that's quite said right. Constant speed usually refers to highway driving (vs city) which usually means higher speed. Yes, higher speed is bad for efficiency. But constant speed (if it's a flat road) is actually good for efficiency. It means you're never having to slow the car down (until the end). Slowing the car down (regen, whether applied with CC, accelerator pedal, or brake pedal) does recapture most of the energy, but not all of it, and you need to burn more energy to get back up to speed. You might recapture 0.9 kWh on regen slowing but burn an extra 1.0 kWh to get it back up to speed (a loss of 0.1 kWh vs not having to slow the car down then speed it back up).

But again, that's often not possible. Just depends on the road, and how flat it is, and whether it has downhill stretches that require slowing the car down from a coasting downhill runaway.

And also how much traffic is on the road that causes the car to slow down/speed up a lot. In traffic, ACC use may be worse by slowing the car down more/sooner than we might drive it manually.

All this is pretty insignificant, of course. Fun exercise to talk about but I doubt it adds up to anything very meaningful. The only time most people care about efficiency is on a road trip trying to cover a long stretch to the next charger.

 

[W1NGE]

I don't think that's quite said right. Constant speed usually refers to highway driving (vs city) which usually means higher speed. Yes, higher speed is bad for efficiency. But constant speed (if it's a flat road) is actually good for efficiency. It means you're never having to slow the car down (until the end). Slowing the car down (regen, whether applied with CC, accelerator pedal, or brake pedal) does recapture most of the energy, but not all of it, and you need to burn more energy to get back up to speed. You might recapture 0.9 kWh on regen slowing but burn an extra 1.0 kWh to get it back up to speed (a loss of 0.1 kWh vs not having to slow the car down then speed it back up).

But again, that's often not possible. Just depends on the road, and how flat it is, and whether it has downhill stretches that require slowing the car down from a coasting downhill runaway.

And also how much traffic is on the road that causes the car to slow down/speed up a lot. In traffic, ACC use may be worse by slowing the car down more/sooner than we might drive it manually.

All this is pretty insignificant, of course. Fun exercise to talk about but I doubt it adds up to anything very meaningful. The only time most people care about efficiency is on a road trip trying to cover a long stretch to the next charger.

Motorway driving at a constant speed of 70 mph is not good particularly when cruise control is active.

 

[Fly4ever]

On a flat and without traffic motorway at 70 mph (112Km/hour) constant speed at this time of year with OAT around 12°C without cruise control and as steady foot as possible I consume 1%/5Kms (3.1 miles). With approx 1kWh/5Kms I get a total range of 475-500Kms (295-310 miles). Snow tyres on 20' wheels.
With everything else remaining the same and constant speed @75 mph (120Km/hour) the SoC looses 1%/4.5Kms (2.8 miles) so calculated range is reduced to about 420-430 Kms (265 miles).
@80 mph (130Km/hour) every 4Km (2.5 miles) I loose 1% of my battery therefore my calculated range is 380Km (235 miles).
Obviously all these calculations are almost impossible to meet a real life scenario as it wouldn't be possible to keep the same constant speed @70 or 75 or 80mph undisturbed for such a long distance of 380-500Kms constantly.

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