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.​

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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.

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