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Discussion Starter · #1 · (Edited)
I have a 2016 Volt and have been reading a little bit on techniques to extend EV range.

The question I have is on acceleration. Should we reach our top speed accelerating as slow as possible, Fast as possible, or somewhere in between?

I had always assumed slow acceleration from a stop. One article even suggested cruise-control as soon as able and use the cruise control acceleration button to gradually get to your top speed.

However... now I'm questioning this after reading this article on hypermiling:
http://www.wikihow.com/Hypermile

This article suggests brisk acceleration to your top speed.

For you long time volt owners, what do you suggest? Have I been accelerating slow for no reason?
 

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Hypermile works on Gas only cars. Gas engine has a peak efficiency at high RPM range.

EV peak efficiency is near zero, so the slower the acceleration the better your range. You can test it yourself, drive like mad and then another time cover the same distance but drive like a grandma.
 

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With a transmission they are trying to get the a higher gear ratio faster as well... you don't have that issue in an EV (unless you are still going through a transmission like the Audi A3...I think it still passes through) but the Volt with a steady increase is preferred and you can get to 30 mph quickly without trying to hard.

I don't think you have to baby it but it doesn't hurt. Dropping the pedal is going to consume a good chuck of power and even that little extra could have gone to just keeping a steady speed for another mile or two.
 

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There has been some suggestion on ICE cars that getting quickly up to speed may increase mileage by getting the car into the more efficient gears sooner. Based on what I've read, I don't think that is the case at all with the Volt.

Personally, with respect to acceleration, I don't notice much of a difference in range unless I'm flooring it continuously throughout a drive. The biggest mileage killer is speed due to wind resistance.
 

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There is a green ball on the left side of the display. The ball goes up or down depending if you are accelerating or decelerating. To achieve peak efficiency in a Volt, keep the 'Ball' green. When you accelerate or decelerate too fast , the ball turns yellow.
 

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The question is how efficiently does the car produce power at different power output levels. That article is about the efficiency vs. power output of an ICE engine, so not necessarily relevant to an electric motor. As far as I understand, it turns out that an electric motor does have a similar relationship between power and efficiency. But the Volt has the complexity of having two different electric motors of different sizes and may engage them in combinations, each of which probably has a different level of efficiency. So if you floor it, you probably get into a less efficient configuration optimized for response rather than range.

There is an indicator on the dash (at least in the gen 1) that helps you keep the car in the efficient zone. It seems to want gradual, somewhat sluggish acceleration. If you hit the resume button on the cruise control, you get pretty good acceleration and the dash indicator stays pretty well centered. I use that method.
 

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Brisk acceleration won't hurt efficiency much, with ICE very little. The worst thing with any car is changing your speed when you don't need to (accelerating up faster than you need to then having to slow down again, especially at highway speeds).

Electric motors have similar efficiency maps to gas cars, they have a most efficient RPM range and it is usually not near 0 RPM (they tend to produce max torque there, but are not the most efficient since they are burning a lot of current at max torque).
 

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Peukert effect: Losses to battery internal resistance vary exponentially with current.

That is, the more instantaneous power you ask of a battery, the more energy is lost to internal resistance.

Short answer: Gentle acceleration.
Fun answer: It's a much smaller amount than in a gasoline powertrain going to "open loop" operation. Peukert's constant for lithium-ion batteries is very close to 1.
 

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I think the reason you don't see a big drop in EV mileage by lead footing it, is that the battery isn't anywhere near it's max discharge rate. IIRC, the packs were rated at 20C discharge? ie - 20 times kWh capacity, or for a 17kWh pack, 340kW, three times the peak controller programmed discharge rate. As far as the battery is concerned, you never get your foot more than 1/3 the way down. If you are accelerating moderately, say 35kW, it's barely feeling it yet.

Someone can correct me if I'm wrong.

Gas engines suffer a lot from a lead foot due to something called power enrichment, and they can't recover kinetic energy. The AF ratio falls during acceleration. Crusing down the freeway you might be 14.x:1 air/fuel ratio. Mash the go pedal and it can fall as low as 10:1 on some cars, but more normally 12:1. Blasting off first sucks down more fuel per HP generated, then the velocity is just burned off as brake heat.
 

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A real-world example of this is driving in Normal versus Sport mode. Even though the difference is barely perceptible, you'll see a difference in energy usage.
I don't see a difference in normal and sport, I have seen my best range of over 50 miles in my 2012 in sport mode, lead footing every acceleration (just not many of them and not at high speeds).
 

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I don't see a difference in normal and sport, I have seen my best range of over 50 miles in my 2012 in sport mode, lead footing every acceleration (just not many of them and not at high speeds).
Interesting. I've gotten better about gently accelerating in Sport, but I still usually see about a two to three mile range difference. When intentionally accelerating harder, I usually see about five miles less range.
 

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The "mid-travel" pedal mapping in Normal is so bad I can't use it. "Nothing, nothing, nothing, nothing, EVERYTHING!!!

I think remapping the pedal to something more linear is my #1 reason for wanting to hack the damn ECU.
 

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Running an ICE at wide-open-throttle is more efficient, therefore, hypermilers use this technique. It's a pulse and glide technique that really tees-off normal drivers. It is best to have a stick-shift so that the gears are manually select-able as early as possible.

Volt is primarily an EV with one gear, so, ICE techniques don't work. Max torque, unlike an ICE, is near zero RPMs. I'm no hypermile expert, but, I'm guessing that slow and stead is better for Volt.

/Not a hypermiler. More a save-time-miler. Best speed to Regula and such.
 

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Medium.

The motor and inverter efficiency is still a curve (albeit flatter than an ICE).
Too little or too much output are inefficient.
Maximum efficiency is somewhere in between.

Just drive it like a normal car in accelerating and you'll be pretty much near max efficiency.
However, even if you floor it, you probably won't see much of a difference in the end - so long as, like mentioned before, you're not flooring it to come to a stop at the next light.
For example, freeway onramp flooring it vs 50% of max won't make much difference in the grand scheme of things. It's having to slow down again that kills efficiency the most.
 

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The answer changes when you're using the battery to heat the cabin. Since you now are pulling a heavy load even if the car is not moving, completing the trip more quickly may result in a lower trip energy usage, even though more aggressive driving is, by itself, less efficient.
 

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For EVs, it seems like the power being consumed is power = resistance X current^2. So, doubling current will multiply power consumption by 4x. There are lots of factors that will change this: e.g., resistance may not be constant. Getting to speed faster and then coasting might sometimes win when power consumption is higher for heating, etc. I still haven't figured this out to my satisfaction.

For conventional gas engines, hypermiling gains because, as others have said, you are running the engine in a more efficient mode. The other thing hypermilers sometimes do is pulse (give it the gas) and glide in neutral with the engine turned off. I've done this gliding with the engine off, but you've got to be really careful; it's not entirely safe (are the airbags still working? you might get only a couple stops before the power brakes stop being powered, etc.)
 

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You want to hypermile your ICE engine, the first thing you need to do is dyno it. You want to always stay in the "fat" area of the torque curve. Datalog it to insure power enrichment doesn't occur. This is the RPM and throttle position you want to be at.

Engines that are able to stay out of the PE tables, and make 90% of peak torque at low RPM are the weapons of choice.

That's why you'll never catch a diesel with a gasoline powerplant. They don't have PE, and make full torque at a very low RPM.
 
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