Bolt can’t really “coast” in D because it’s simulating the feel of an ICEV by doing a bit of regen. So if you’re referring to coasting by taking the foot off the acceleration pedal in D, question becomes essentially like asking whether a low amount of regen is more efficient than a high amount or not. In that case I found the difference to be minimal.

if you’re really coasting, as in keeping the energy expenditure at really close to 0kW on the dashboard no matter what, then it should be technically more efficient than using regen. But that would take a really long time to come to a stop and thus not be practical.

So you should just use any form of regen to come to a stop and avoid using physical brakes in order to be efficient.

 

I found that "coasting" to be more difficult estimating stopping distance.

 

It's more energy efficient to regen to a stop because you're adding energy back into the battery. Coasting, if you can do it, doesn't add energy back.

 

You will NEVER regen 100% of what you consume. Can't happen. 'cause Physics.
Coast using 0kW >> Regen'ing anything.

So this statement....127% perfectly incorrect.

Next.

 

This topic always seems to generate passionate opinions both ways. My experience (88K miles) suggests it makes so little difference if you drive relatively efficiently that it probably isn't worth getting worked up about it. I mean, a .1 mi/kWh difference is so insignificant that one has to ask, why bother sweating over it?

Hypermiling requires patience and skill well beyond what most drivers can accomplish consistently. Add unpredictability of conditions (climate or other drivers) and it is even more daunting to get a good comparison.

 

This topic always seems to generate passionate opinions both ways. My experience (88K miles) suggests it makes so little difference if you drive relatively efficiently that it probably isn't worth getting worked up about it. I mean, a .1 mi/kWh difference is so insignificant that one has to ask, why bother sweating over it?

Hypermiling requires patience and skill well beyond what most drivers can accomplish consistently. Add unpredictability of conditions (climate or other drivers) and it is even more daunting to get a good comparison.

It’s nice to see people passionate about their driving. But I completely agree with you that it’s not going to make much difference. I like using regen or L as an aid to driving, and it is definitely going to save on brake pad replacement. I would suspect that the brakes will never wear-out if regen is always used.

I notice that the regen recouped is about 25% less than the energy expelled by acceleration. So I don’t think that coasting is going to offset the acceleration, but it would lower the energy used for the coasting phase. Which is actually more efficient than the other is only going to answered by a scientific study, but it would be a monumental effort of concentration to try to stay within a coasting discipline while it might be more prudent to be concentrating on the traffic and what is going on around you. YMMV

 

Coasting will always be more efficient because you're using all the energy you can use. The only waste is air resistance and rolling resistance and you can't help those. Well, you can lower air resistance by lowing the speed but at a given speed you'll get a given resistance. If you can coast all the way to a stop you have used all the energy you can use. But, you won't enjoy this. We tend to want to travel at a given speed then slow down more quickly when it is time to stop. You can either regen to slow down or use the friction brakes. Obviously then regen wins as you are putting some energy back. But, the original example is a stop light. If you see the light turn red in front of you then you need to stop. You probably don't have room to coast to a stop. The car will coast for something like a mile if you put it in neutral at 60mph and just coast it. You probably aren't going to time the light right at that point. The best general answer is to coast as much as you can for as long as you can and use regen to slow down the rest of the way as much as possible. That's basically the best you can do.

 

Coasting will always be more efficient because you're using all the energy you can use.

Possibly not always, because;

The only waste is air resistance

While coasting, you spend more time at higher speed so the energy waste due to air resistance is greater. If you regen down to a lower speed quickly, you may see a net gain over coasting due to less waste towards air resistance.

Then there's gravity. Not using regen on a down-slope is a perfectly good waste of gravity.
I did an experiment a while back with the Tesla, which has a very accurate energy usage estimating system based on terrain and other factors. I was at the top of a very long slope and I looked at the expected energy usage graph, which naturally assumed the use of regen to slow down. Well, instead of using regen I allowed the car to speed up and slow down while keeping regen close to zero. This was at speeds of about 60-85 MPH. At the end of the slope the actual energy usage was significantly higher than predicted. How could this be if I spent a significant amount of time coasting instead of using wasteful regen? Well, it's because I wasted my potential energy on air resistance instead of using it for regen.

 

I’ve tried both the regen mode and coasting in the D mode and I have found no difference in the efficiency between the two.

like the regen mode better than coasting in D, and that’s become my preferred setting. It now only goes into the D mode if my wife is driving the Bolt. She does not like the regen mode at all.

 

I’ve tried both the regen mode and coasting in the D mode and I have found no difference in the efficiency between the two.

like the regen mode better than coasting in D, and that’s become my preferred setting. It now only goes into the D mode if my wife is driving the Bolt. She does not like the regen mode at all.

I would love to see my wife use any method other than the one she uses. She really likes regen/L, but she also really likes the accelerator. So it seems like she is either accelerating or slowing down. To her coasting seems to be what she mostly wants to avoid LOL

It’s a good thing that a Bolt is so efficient that it really doesn’t matter how it is driven, it’s going to use less energy than about anything else that a particular driver is going to do when they drive it.

Coasting? I usually want to visualize that as having an ocean in view 😉

 

Assume you put the Bolt in neutral, and actually coast to a stop. Say you were going 50 mph when you put it in Neutral. How ever many yards you travel, your average speed for that distance will be 25mph. Now imagine you are in D, L, or CC, going 50 mph. You wait until you are 100 feet from the stop sign, and use regen to stop. Even if you regained 100% of the energy needed to stop, it wouldn't make up for the many yards averaging 25 mph, in the previous example.

 

I use both, with the goal of not totally stopping by the time the light has changed.

 

If you're after efficiency, there's proven ways to increase it:

Accelerate gently, keep the "power' output display on the RH side of the DIC below the top of the oval. Imagine having an egg between your foot and the accelerator.

Slow down: there's a world of difference in energy used between say, 75 Mph and 60 or so. Slowing further from 60 to 50 will make some difference, but not as much as the 75 -> 60 change.

Keep your tires inflated to a bit over the recommended pressure. Watch pressure and adjust as the weather cools when Winter approaches. Tires lose about 1 PSI for every 10 degrees.

These tricks were learned long ago by drivers participating in once-popular economy runs.

 

I drive in L pretty much exclusively. And when I can see waaaay ahead, I engage cruise control. It's surprisingly useful even on thoroughfares posted at 35 mph, and a quick flick of the regen paddle disengages it.

 

Coasting requires being in Neutral, which I personally would never do for many reasons.

And Coasting in Neutral does NOT turn on the brake lights, which regen in L does. I almost always drive in L.

 

If by coasting you mean driving in Neutral, I would never do it for many reasons, safety among them. Besides no brake lights on when in Neutral, but I have confirmed that they are on when I drive in L and lift my foot off the accelerator to start Regen.

FWIW: I have driven down the 5 mile Grapevine on Interstate-5 in Southern Kern County in the far right lane behind a semi driving 35 MPH (the posted speed limit for trucks) in L and CC of 35 MPH and gained 1.1 to 1.5 Kw on my gauge, and of course those 5 miles were FREE!

 

Sure, coasting's better, but it will be a minimal difference. And it does also technically save on battery degradation, as you stop pulling power earler, and put less back in. Personally, I'll frequently get off the throttle early (just shift into N, unlike a gas engine, it won't rev the balls out of the motor), coast for a while, and then then come back into D or L to stop. That way I avoid the annoying portion of coasting where you travel at low speed, but also don't use the friction brakes.
Takes a time or two to get the feel for how far from a stop sign you do it at a given speed, but not hard. Am I saving much in the way of range? No.

 

Sure, coasting's better, but it will be a minimal difference. And it does also technically save on battery degradation, as you stop pulling power earler, and put less back in. Personally, I'll frequently get off the throttle early (just shift into N, unlike a gas engine, it won't rev the balls out of the motor), coast for a while, and then then come back into D or L to stop. That way I avoid the annoying portion of coasting where you travel at low speed, but also don't use the friction brakes.
Takes a time or two to get the feel for how far from a stop sign you do it at a given speed, but not hard. Am I saving much in the way of range? No.

At what speed have you actually shifted from N back to D or are these merely hypothetical musing?

 

Best to coast to stop if you are hypermiling. Bolt doesn't make it easy to coast like the BMW i3 does. It has a detent on gas pedal to let you coast.
EV's are not perpetual motion machines. You may only get 25% of the acceleration power back. That is what my tests show generally. I've tried different velocities and lower speeds should have returned more but even regen on very low current doesn't change a lot from full regen in terms of efficiency. .

 

Best to coast to stop if you are hypermiling.

This is key to this discussion.

If we are simply comparing coasting to a stop vs using one pedal driving to slow to a stop, regenning will be more effecient.
The distance traveled is the same in both cases. In one case you used 0kw of energy, n the other you put "some" energy back into the battery.
-But-
if you are hypermilling that is a totally different animal. When hypermilling you are trying to get the most distance out of 0 energy as possible. Regen will limit the amount of distance you will "coast". Hypermilling will be actuall coasting a lot more than you would be regenning over an entire trip which would likely be much more effecient than regenning all the time and then having to accelerate again (usin gmore power than you regenned).

So if you are actually hypermiling then coasting is more efficient.
If we are talking about general stop and go regen is better (arguable as to how much, but definitely more efficient)

 

Really good drivers maybe are able to coast down in Neutral from 60MPH to 15MPH, then apply brakes for a full stop. Doesn’t sound too good, but energy saved is the square of the speed. If you can stay off your brakes till 15MPH, you are saving 93+% of driver “inefficient” braking energy from 60MPH. As for me, I’m happy when I can coast in Neutral down to 20MPH before having to brake to a stop.
However, we’re not talking about a more important aspect & that is battery stressing. Drawing energy OUT of the battery while at 60MPH in L or D, AND then adding that same energy BACK INTO the battery while slowing & regenerating is a terrible thing to do. If the battery is to last 300,000+ miles, extracting energy from the battery while in D or L, AND putting energy back into the battery while regenerating is the thing…..NOT TO DO.
Who would have thought that doing nothing while coasting in Neutral could be so doubly good for the battery!

 

However, we’re not talking about a more important aspect & that is battery stressing. Drawing energy OUT of the battery while at 60MPH in L or D, AND then adding that same energy BACK INTO the battery while slowing & regenerating is a terrible thing to do. If the battery is to last 300,000+ miles, extracting energy from the battery while in D or L, AND putting energy back into the battery while regenerating is the thing…..NOT TO DO.
Who would have thought that doing nothing while coasting in Neutral could be so doubly good for the battery!

Yes, No, Maybe. There is not yet sufficient data to prove coasting would reduce battery degradation over time. You say it definitely would. Another might say with equal confidence, "If coasting would extend the life of the battery and reduce GMs warranty liability, they would have built in a coasting mode."

jack vines

 

Not easy to hypermile in my town.

 

Same here. But, I love to travel the slower back roads with a bit less traffic trying to push you faster on the road.

 

Regen is not 100% efficient, so if you're using it when not really necessary then you're wasting energy. For example, if you're approaching a red light on a slight upgrade, better to let the energy you've already expended in getting the car up to speed carry the car up to the light while being slowed by gravity. If you power up to the light and then use regen to stop, you're expending extra energy to go up the grade and you're not recouping it all by stopping with regen.

That having been said, when you actually require braking force (i.e, downhill grades, unexpected stops) then having regen to recover most of your momentum into energy is way better than not having it.

Note that you get regen even while using the brake pedal in D mode, so you don't have to be a one-pedal driver to benefit.

Note also that you don't need to go from L into N to coast - you just need to apply the right amount of pedal pressure to maintain roughly 0 on the power meter.

 

I drive on rural roads with very little traffic. When I see a train about to cross and there's no one behind me I just let the car coast from a long distance. There's no point rushing to get to a railroad crossing and then wait 5 minutes. I do love one pedal driving in the Bolt more than in the Volt. The regen in the Volt isn't aggressive enough. I end up using the regen paddle most of the time. But the Bolt's regen is strong and somewhat predictable. I can feather the accelerator pedal or use the regen paddle as needed.

 

Before I would even dream of putting my transmission in neutral while the car is traveling at speed, I would make completely sure that everything cooling wise and lubrication wise is in full operation, and specially pressurized lubrication. If anything shuts off from being in neutral it is going to be a very expensive lesson. And the motor always turns. There are permanent magnets that are trying to generate some energy without back feeding and power into the stator coils to max the regen.

I just don’t know enough about the design of the bolt propulsion unit, and the last people I am going to listen to about it are people speculating on an Internet forum. I don’t want anyone to take personal offense, but I don’t trust a single thing I read about this type of discussion.

The minuscule amount of generation that is going to happen due to rotating magnets is something that neutral on the transmission shifter is not going to change. I think the only reason for the neutral is for a car wash conveyor to pull the car through.

Good luck hypermiling for ant shite return. I don’t chase rolling nickels because there is much more meaningful ways to save. Like combining trips. I challenge anyone to get a lower energy use than performing two trips in one occasion by planning ahead.

But don’t let me change the hypernerding discussion if it’s what blows up anyone’s skirt. YMMV

 

I do not think there is a measurable difference in the efficiency of regeneration between one-pedal deceleration and coasting to stop. At the same time if get green before you completely stopped, you will use less energy accelerating back to the travel speed. So, all things considered, coasting (as a habit) is probably going to be somewhat more efficient. Regardless, I always use the one-pedal drive function, as IMO it's safer.

A corollary question perhaps could be, What's the max regen capacity of the Bolt - would it be the same 55 kW as [GM says] you'd get at an adequately powered L3? I forgot what was the highest level was that I observed.

 

I do not think there is a measurable difference in the efficiency of regeneration between one-pedal deceleration and coasting to stop. At the same time if get green before you completely stopped, you will use less energy accelerating back to the travel speed. So, all things considered, coasting (as a habit) is probably going to be somewhat more efficient. Regardless, I always use the one-pedal drive function, as IMO it's safer.

A corollary question perhaps could be, What's the max regen capacity of the Bolt - would it be the same 55 kW as [GM says] you'd get at an adequately powered L3? I forgot what was the highest level was that I observed.

I have heard it’s 70kW. I have never looked to see what the kW meter can max at, but I have seen more than 60.

What I have noticed is what the CC does when it gets put on resume after coming to a stop. I will hit resume at about 20 mph, and the CC will get up into the high 60’s. And that is almost to the point where the big ring color starts to change to yellow. The CC will use right below the threshold for inefficient acceleration.

Using friction brakes will also turn the big ring yellow. I am always watching for where I am going to come to a stop to really look at the kW meter so I have never seen the in regen/paddle full output for regen.

 

Coasting as in no energy used nor regenerated ? True, coasting is more efficient, but I doubt it is THAT more efficient. So just drive and enjoy ! The Bolt EV is a very efficient car either way.
I like to keep sometimes the energy usage to zero, so I play with the acceleration pedal but that’s only for fun…

 

One should drive a BMW i3 and see how easy they made putting motor in a freewheeling state. No input or output power. I state that driving in N is dangerous. Don't attempt it in Bolt except in car wash mode.

 

I've seen over 70kW on regen, and 150kW at full throttle. The battery and associated electronics are designed for it. I seriously doubt the charge/recharge that happens from regen will have any measurable impact on the battery's overall life

 

Somebody played a card.

 

But most people get butthurt early and get butthurt fast these days.