One pedal drive (vs) Brake regen

[Space Ghost GT]

Here is another picture.

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[AKgrampy]

I see where you are going, but you have to check your assumptions. Try to focus on energy loss. In the example earlier where you make the decision to "coast" into the stop in 2P mode, you have the potential energy that is being converted to kinetic energy (moving the car towards the stop), such that it will perfectly run out of energy when you come to a full stop. You are assuming, because you did not apply the brakes that there was no waste other than the friction of the road and the resistance from air which are arguably equal in both 2P and 1P mode.

You then postulate, that if you are slowing down using 1P mode by easing off of the accelerator and thus reducing energy input (but still putting in some energy) and generating some electricity to charge the battery; you are actually worse off because regenerating electricity is not 100% efficient and therefore you were better off with the coasting than you are with the regen.

I agree with that. The problem is with the assumption that you coast to a stop and never touch the brake which is the only way to achieve your coasting efficiency. I cannot guarantee, but I'm pretty certain that your coasting inefficiency far exceeds any regen inefficiency.

One of the early posts for 2P was 90% efficient, versus >98% for 1P. Sounds about right to me.

Only way to coast is to shift to Neutral. Otherwise unless heavy on the brakes regen in 1PD overall is equal to regen in 2Pd. Simple as that!

 

[mfbrown]

Talk about a bad look it’s hilarious your telling me I don’t own a Mach e when it’s sitting in my garage.
read and weep I’ll take my 100 dollars. You need to get a handle on your emotions.
https://www.roadandtrack.com/car-cu...rily-the-most-efficient-way-of-driving-an-ev/

I thought that might be the article you read. I think the title says it all, "... Isn't Necessarily..." It is not a conclusion from an exhaustive study of 1P vs 2P; it is a thoughtful analysis of different approaches and comparing multiple systems for energy use and capture; Porsche believes their solution doesn't require 1P to be efficient.

That's why in my earlier post I said that it does not make sense to compare different manufacturers. The question is on a Mach-e and whether 1P or 2P is more efficient. Porsche is a completely different beast with a different implementation of 2P which includes a blended braking system designed to obviate the need for 1P. It may even be better than the Mach-e solution, but last I checked there is no button on my screen to pick 1P or Porsche 2P.

 

[mfbrown]

Only way to coast is to shift to Neutral. Otherwise unless heavy on the brakes regen in 1PD overall is equal to regen in 2Pd. Simple as that!

Is that true? I have used 2P and coasted (while in drive) and it certainly feels like there is very little regen slowing the car down. I have been amazed (coming out of 1P) how far it will coast. Never tried it in neutral, but I haven't done that with a car since I had a stick.

I'm not saying you are wrong, because I'm not doing any calculations to defend my statements, but from a conservation of energy perspective, I'm not sure they would be equal between 1P and 2P if you coasted to a stop. My reasoning is that If I am going 50 mph and take my foot off the accelerator in either mode, then measure how far the car rolled in each case: X feet in 2P mode or Y feet in 1P mode. I think we would agree that X > Y. Therefore, more of the energy stored in the car of mass M moving at 50 MPH at time 0 went into moving the car in the case of 2P and more of the energy in the case of 1P went into charging the battery.

 

[mkhuffman]

Here is another picture.

Oh, yes! Another white GT owner!

This argument about which driving mode is more efficient is ridiculous, IMO. The MME is not an efficient BEV. If you really care about wringing the most efficiency out of a mile, you purchased the wrong car.

If I coast to a stop after a WOT to 80 mph, is that more or less efficient in 1PD or 2PD? Who cares! Just pick the mode that gives you the most enjoyment and drive your car!

Anyway, here is my white GT. And it sees a lot of WOTs.

 

[AKgrampy]

Is that true? I have used 2P and coasted (while in drive) and it certainly feels like there is very little regen slowing the car down. I have been amazed (coming out of 1P) how far it will coast. Never tried it in neutral, but I haven't done that with a car since I had a stick.

I'm not saying you are wrong, because I'm not doing any calculations to defend my statements, but from a conservation of energy perspective, I'm not sure they would be equal between 1P and 2P if you coasted to a stop. My reasoning is that If I am going 50 mph and take my foot off the accelerator in either mode, then measure how far the car rolled in each case: X feet in 2P mode or Y feet in 1P mode. I think we would agree that X > Y. Therefore, more of the energy stored in the car of mass M moving at 50 MPH at time 0 went into moving the car in the case of 2P and more of the energy in the case of 1P went into charging the battery.

There are others who have done sophisticated calculations but think of it this way - you put x amount of energy into you car to accelerate. As you slow down that is either lost to friction or reclaimed by regeneration. So maybe a higher regen has larger heat losses in the regen load but then a longer regen (coast) involves more friction. Bottom line, I believe, as long as you do not hit the friction brakes then the regen from 1PD is equal to 2PD. Unless someone can explain where the energy is lost between the two modes. We are speaking in general and not a special case such as “What about a long downhill drive?” (Which May still be the same but my brain already hurts!)

 

[Geesh]

There are others who have done sophisticated calculations but think of it this way - you put x amount of energy into you car to accelerate. As you slow down that is either lost to friction or reclaimed by regeneration. So maybe a higher regen has larger heat losses in the regen load but then a longer regen (coast) involves more friction. Bottom line, I believe, as long as you do not hit the friction brakes then the regen from 1PD is equal to 2PD. Unless someone can explain where the energy is lost between the two modes. We are speaking in general and not a special case such as “What about a long downhill drive?” (Which May still be the same but my brain already hurts!)

If you were correct, wouldn't you guarantee 100% braking efficiency in 1PD(assuming no mechanical brake use by driver).. since we know that's not the case, if we are to believe the car itself, there has to be a loss of efficiency depending on the amount of regen introduced.. ie. Complete depress of accelerator results in max decel.. which is not allowing full recapture of energy... for whatever reason. That's my crude explanation how 1PD could introduce inefficient regen. Although... I assume that same situation could be present in 2PD.. it's just harder to isolate. Or my head just hurts... this is fun!!

 

[mkhuffman]

Is it faster to 80 mph if I am using 1PD, or 2PD?

 

[AKgrampy]

If you were correct, wouldn't you guarantee 100% braking efficiency in 1PD(assuming no mechanical brake use by driver).. since we know that's not the case, if we are to believe the car itself, there has to be a loss of efficiency depending on the amount of regen introduced.. ie. Complete depress of accelerator results in max decel.. which is not allowing full recapture of energy... for whatever reason. That's my crude explanation how 1PD could introduce inefficient regen. Although... I assume that same situation could be present in 2PD.. it's just harder to isolate. Or my head just hurts... this is fun!!

You are correct in that it would be the same in 2PD. So if you are driving light to light you put x amount of energy into acceleration and get Y out in regen and Z in resistive losses and X = Y + Z. My thoughts are that unless you brake hard Y and Z are the same for both modes. Of course if you reef on the brakes in 2PD your resistive loses will be greater and you lose regen.

 

[AKgrampy]

Is it faster to 80 mph if I am using 1PD, or 2PD?

Or even more important - Is it further to Kansas City or by bus?

 

[Ming]

ok, I am going all nitty gritty here.. please bear with me

Lets say in 2PD:
I am driving 40 mph and I see a red light(about 100 meters) and I remove foot from accelerator, car coasts and I apply brakes at the light (lets ignore 95% regen here)

same scenario in 1PD:
I have to take the foot off the accelerator at (lets say) about 50 meters (regen)

so with 2PD, I drive 100 meters with out consuming energy(coast)
and with 1PD, the regen I got (from 50 meters) will not take me 100 meters(it may take me to 40 meters only)

So I think 2PD is efficient (because of coasting).
Imagine doing this many times while we drive.

I know I am not taking real world example, but I hope you get my point.
Feel free to point my mistakes

My quick calculation shows a MME at 5000lb driving at 40MPH to a stop has about 200Wh energy to be converted to other type of energy.

You 2PD case, the energy mostly converts to heat and releases to the air.
1PD case, mostly goes back to the battery.

I don't know why you think wasting on brakes is better.

 

[Terence Murphy]

Was it stated if time is a constant, ie light to light you’re taking the same time? To truly gain efficiency by coasting, you have to coast. Meaning start coasting very early with the aim of coasting to a stop at the light without your brakes. And pissing off everyone behind you. And taking more net time than you would otherwise for the distance.

if you’re not pissing off the traffic behind you, I doubt you can manage to exceed regen efficiency.

WRT the actual regen efficiency, does anyone have data on true regen efficiency compared to what the Ford software reports? 1PD without hitting the brakes will use the friction brakes at the end, and I believe still reports 100% on a cold battery that won’t truly take all the charge (not positive on that since I don’t have a scanner and I haven’t tested in depth, but fits with what I’ve seen this winter). All it really means is you couldn’t have used less friction braking. I.e. it’s a relative efficiency, not absolute.

 

[HowdyDoody]

Whisper mode, 2PD. If you want to long coast, shift to neutral. Medium coast remove foot from pedal. Regen stop, press the low button. Its a game to minimize the brake. Its more efficient than 1PD. You can do it.

 

[AKgrampy]

My quick calculation shows a MME at 5000lb driving at 40MPH to a stop has about 200Wh energy to be converted to other type of energy.

You 2PD case, the energy mostly converts to heat and releases to the air.
1PD case, mostly goes back to the battery.

I don't know why you think wasting on brakes is better.

I do not know whether to laugh or cry at some of the comments that are being made. Your point about energy needing to be converted is right on and that does not matter if you coast or not. The thing that is driving me crazy; though, is that people do not realize that 2 PD is 100% regenerative braking if done smoothly. So my guess is both methods are close to the same efficiency.

 

[mkhuffman]

So my guess is both methods are close to the same efficiency.

This is the answer! Drive mode doesn't reduce efficiency, the way you drive does!

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