Chevy Bolt EV Forum banner

1 - 20 of 81 Posts

·
Registered
Joined
·
118 Posts
Discussion Starter #1
Hi Everyone,

I am wondering what is the most efficient way to accelerate from a stop light. In gas cars, there is such a thing as accelerating too slowly, which results in using more fuel.

Is this the same for electric cars? So, is it better to gun it a little and use 30 kW until you reach your desired speed, or use 12 kw and slowly reach your speed?
 

·
Registered
2020 Chevrolet Bolt
Joined
·
202 Posts
Hi Everyone,

I am wondering what is the most efficient way to accelerate from a stop light. In gas cars, there is such a thing as accelerating too slowly, which results in using more fuel.

Is this the same for electric cars? So, is it better to gun it a little and use 30 kW until you reach your desired speed, or use 12 kw and slowly reach your speed?
Purely from the perspective of air and rolling resistance, it's more efficient to accelerate slowly because it lowers your average speed.

From the perspective of losses in the electrical system, if accelerating hard causes the battery and motor to heat up, that implies some thermal losses (from inefficiency in converting electrical energy to kinetic energy).

Having said that, I don't know for sure. For any given EV, there might be an ideal acceleration > 0.

Edit: I failed to answer your actual question. Is it better to gun it a little? Why yes it is. In fact, it's even better to gun it a lot. ;)
 

·
Registered
Joined
·
7,963 Posts
An EV uses the exact same amount of energy to accelerate to 60 mph whether it takes a second or a minute according to CleanTechnica.
As liuelson said, there will be some tiny difference in motor efficiency. That difference would be so small as to be a total waste of time to look for. I am sure there are engineer geeks on here who are rushing out to measure it right now. ;)
 

·
Registered
Joined
·
609 Posts
The laws of physics agree with Martin D assuming there is no change in efficiency of the motor, battery, cable, etc. However once you are at speed, the energy required to maintain the velocity goes up as the velocity squared (in meters/second). So once you are going faster, you will use more energy.

Personally I have found the most efficient way to accelerate is downhill. :);)
 

·
Registered
Joined
·
289 Posts
As liuelson said, there will be some tiny difference in motor efficiency. That difference would be so small as to be a total waste of time to look for. I am sure there are engineer geeks on here who are rushing out to measure it right now. ;)
It is an interesting article. I am on my phone and not through tapatalk so I will let someone else find the url.

“How EV Range is affected by Hard Acceleration “

-by Andy Miles
Published April 16, 2018 in CleanTechnica

He goes on to say that people are not capable of regulating speed to plateau at and will end up driving faster at any given point in time while hard accelerating, and friction loss (rubber too). Heat generated in the motor windings increases also meaning the motor itself is loading energy in the form of heat instead of kinetic energy.

What I have noticed is our cruise control. If you hit “resume” at a much lower speed than it is set for, the acceleration is neither sluggish or gentle. I would say more like “brisk” , maybe 50 kW load.

edit: “How EV Range is affected by QUICK Acceleration “. (My bad)
 

·
Registered
2017 Bolt Premier
Joined
·
437 Posts
An EV uses the exact same amount of energy to accelerate to 60 mph whether it takes a second or a minute according to CleanTechnica.
Really? So if I floor it or creep my way to 60, the total energy expenditure to that point would be the same? Interesting.
 

·
Registered
Joined
·
118 Posts
Discussion Starter #10
An EV uses the exact same amount of energy to accelerate to 60 mph whether it takes a second or a minute according to CleanTechnica.
Wow, that is fascinating. So, all things being equal, just drive however you feel like driving at that time. Slow if you are in a mellow mood and briskly when you feel like it since the energy used is roughly the same.
 

·
Registered
2020 Chevrolet Bolt
Joined
·
202 Posts
It is an interesting article. I am on my phone and not through tapatalk so I will let someone else find the url.

“How EV Range is affected by Hard Acceleration “

-by Andy Miles
Published April 16, 2018 in CleanTechnica

He goes on to say that people are not capable of regulating speed to plateau at and will end up driving faster at any given point in time while hard accelerating, and friction loss (rubber too). Heat generated in the motor windings increases also meaning the motor itself is loading energy in the form of heat instead of kinetic energy.

What I have noticed is our cruise control. If you hit “resume” at a much lower speed than it is set for, the acceleration is neither sluggish or gentle. I would say more like “brisk” , maybe 50 kW load.

edit: “How EV Range is affected by QUICK Acceleration “. (My bad)
Here you go:

The author did try to test whether hard acceleration made a difference, and for his test, it resulted in 7% more energy used over a 30 mile trip.
 

·
Registered
Joined
·
118 Posts
Discussion Starter #13
He goes on to say that people are not capable of regulating speed to plateau at and will end up driving faster at any given point ....

What I have noticed is our cruise control. If you hit “resume” at a much lower speed than it is set for, the acceleration is neither sluggish or gentle. I would say more like “brisk” , maybe 50 kW load.
I have noticed that about acceleration: when I floor it I overshoot my target speed. And I have noticed the cruise control is quite brisk in acceleration.

Thanks for the information! :)
 

·
Registered
Joined
·
118 Posts
Discussion Starter #14
Put an extra PSI or so in your tires and you will probably save more energy. Sneak over and put an extra PSI in your neighbors ICE and you'll probably save 10x more energy. Some things are not worth worrying about... IMHO.
My tires are aired up north of 50 psi at the moment (the car doesn't have oem tires.) I aired the tires up on a cold day, and now that it is warmed up I may need to let some air out.
 

·
Registered
Joined
·
289 Posts
Really? So if I floor it or creep my way to 60, the total energy expenditure to that point would be the same? Interesting.
The physics of it it may be true but in the reality of it humans are for the most part incapable of the smooth application of power ending in the exact speed targeted, and need to slow the acceleration to something easier for us to react to. We have to keep the car in the lane while calibrating a roll-off of the acceleration to exactly end at the target speed.

That was a long way of saying the Cruise Control is way better at it than any of us. Just drive normal, but letin’ ‘er rip on occasion will cost you not because you punched it up to the speed limit, but because you went past it before backing off.
 

·
Registered
Joined
·
118 Posts
Discussion Starter #16
Here you go:

The author did try to test whether hard acceleration made a difference, and for his test, it resulted in 7% more energy used over a 30 mile trip.
I looked through the article. That is amazing actually. The difference between max acceleration and gentle acceleration is only 7%. Wow!
 

·
Registered
Joined
·
1 Posts
Good Day,

Energy use will be the same -- in theory -- to arbitrary speeds. Having said that, hard -- fast, pedal to the metal acceleration -- will cause more wear on the battery as you are drawing more power which creates more physical stress (the side effect being additional heat on the battery pack). Steady acceleration is best in my opinion, though it's fun to give it some juice.
 

·
Registered
2017 Bolt Premier
Joined
·
437 Posts
I looked through the article. That is amazing actually. The difference between max acceleration and gentle acceleration is only 7%. Wow!
That’s interesting. Not sure a 30 mile trip is enough to draw a conclusion, but if it’s accurate over the lifetime of a car/battery, that’s pretty amazing!
 
1 - 20 of 81 Posts
Top