Pulse and Glide (Coast and Burn) Calculator for EV's

[CoulombMotorsport]

Coast and Burn (Pulse and Glide) Calculator

Postby CoulombMotorsport » Thu Jan 28, 2016 2:45 am
Hi all,

So my brother and I are from Perth, Western Australia and we have been building electric endurance vehicles in our garage since 2009 when I was 15 and he was 11. We've now built Australia's most efficient manned land electric vehicle, which achieved 131.7 km/kWh (on a very windy day) and although we're not eligible for the Shell EcoMarathon competition (as we're not an educational institution) we're currently trying to beat the Australasian record of 434 km/kWh.

To try and improve our vehicle's efficiency we're not only improving the vehicle's components but trying to develop a very efficient strategy for the driving of it. One of the most popular fuel saving strategies used by hyper-milers is Coast and Burn (a.k.a Pulse and Glide) but there is very little information currently about it online so I decided to do my own theoretical research to estimate it's effectiveness.
In the following topic, I'm trying to develop a calculator to determine the effectiveness of a Coast and Burn strategy using an excel spreadsheet which takes the following inputs;
- Crr (co-efficient of rolling resistance)
- Cd (co-efficient of aerodynamics)
- Frontal area of the vehicle (m2)
- Mass
- Burn Speed (what speed do you accelerate to?)
- Coast Speed (what speed will you coast down to?)
- Motor Power

and then provide the user with the following information:
- How far will you coast?
- How long will you coast for?
- How far will you burn (pulse) for?
- How long will you burn for?
- Percentage of time spent burning/ percentage of time spent coasting
- wH/km for Burn/Coast Strategy
- wH/km for Constant Speed Strategy

[CoulombMotorsport]

So the actual calculator is in an excel spreadsheet and is explained in a short-ish video at the following youtube link:

www.youtube.com/watch?v=GQp0u5-NE6I

The link to download the calculator is in the comments.

Kind of unsurprisingly, I've found that Pulse and Glide doesn't work for the vast majority of electric vehicles as the efficiency of the motor doesn't vary greatly.

[sendler]

Does Pulse and Glide actually hurt efficieny with an electric vehicle due to heat losses increasing as to the square of the increased current? Or it doesn't really matter, coming down to simply what speed you end up averaging.

[CoulombMotorsport]

Hi sendler, given that motors have fixed iron losses in their stators they have peak efficiency bands just like gasoline engines. So even though you're putting more power through the motor and hence the heat losses are higher, it's actually more efficient (89.5% in my motor's case) to run at a higher amperage (13A) than the constant speed current required of 4A (where the efficiency is 84%). However, given that at a constant speed you're not expending additional energy accelerating and because the efficiency is pretty close anyways it works out better to maintain a constant speed.

[Gasoline Fumes]

Originally Posted by CoulombMotorsport

...it works out better to maintain a constant speed.

Just on flat ground, or it is that true on hills too?

[sendler]

Do you have a thread or web page about the vehicle?

[CoulombMotorsport]

@Gasoline Fumes
On hills, we've found it is more efficient to burn as the vehicle requires more torque (more amps) to pull up the hills and so if you burn hard and go up faster you spend less time at full power. Once we've gained height we then freewheel down the hills as much as possible during which time the motor doesn't use any power at all.

[CoulombMotorsport]

@Sendler, we certainly do. Not much info at all about our current efficiency car as it only launches March 12 and so it's under wraps at the moment.

Our website (rather outdated) is: Coulomb Motorsport | Home
Facebook page (public): www.facebook.com/CoulombMotorsport
and our YouTube channel (most up to date) is: https://www.youtube.com/user/CoulombMotorsport

I hope you find it informative. Any suggestions or questions, please let me know.