Continous drive or accelerate and coast ?

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ofx210p
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Continous drive or accelerate and coast ?

This is just something thats been buzzing around my head (whilst i'm riding) for the past few days and i keep forgetting to put on here.

Some of the million milers car drivers (i think thats what they're called), the bunch of people who try to get every last km out of their fuel in cars, often use the accelerate and coast driving method. Apparently because of pumping losses its far less efficient to drive a car at very low revs. There's much more to it but you can google that and read all about it.

However my thoughts were, is there any benefit to using brief moments of acceleration and coasting in using battery power ? or is simply continual low current driving better.

My personal thoughts are that its probably better to have a continual low current drain, however, whats your thoughts.

I guess the easiest way will be to fit the bloody cycle analyst that i've not got around to and then i could answer the question ! lol

MEroller
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Re: Continous drive or accelerate and coast ?

In electric propulsion with direct drive (no gears to shift) it is highly likely that you will get most range at smallest current, creeping along at a walking pace.

In combustive propulsion you get the most range in highest gear and the lowest RPM at which the engine still runs smoothly. As this will be at a far higher speed than walking pace it will take a fair amount of accelerator travel to create the torque necessary to turn the wheels. This will actually reduce the pumping losses of a throttled gasoline guzzler.

And for both means of propulsion it is most important to keep that ideal speed constant, with no braking nor acceleration. So this is only a very theoretcial scenario :-)

My rides:
2017 Zero S ZF6.5 11kW, erider Thunder 5kW

Mik
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Re: Continous drive or accelerate and coast ?

I think gentle is better with a Vectrix.

There is no way of avoiding the losses / friction from the motor continuously spinning, because of the single gear fixed transmission.

I think the hypermilers try to run the ICE for short periods at it's most efficient RPM, then turn it off. To get an idea about the losses saved that way, you can imagine cranking a car engine (with the ignition off) by hand.

You cannot choose the most efficient RPM on a Vectrix, unless you accept to have your speed dictated by that. In that case, about 40km/h is probably best.

P = R * I^2 means that the losses due to battery and cable resistance grow exponentially with the current. Harder acceleration causes disproportionally more heat in the battery and cables.

So basically give it only as much throttle as you need to eventually reach your desired constant speed.
.

I have a related question about coasting on a Vectrix, for example while approaching a red traffic light which is likely to turn green soon.

Would it be more energy efficient to:

A) coast with minimal throttle applied, just enough to make the motor spin at the same speed that the Vectrix is coasting at, keeping the gear box as quiet as possible;

or

B) release the throttle fully while coasting, slowing down quicker, saving energy first but then using more to re-accelerate again?

This information may be used entirely at your own risk.

There is always a way if there is no other way!

Joshteacher
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Re: Continous drive or accelerate and coast ?

I've thought a lot about this since I've been trying to keep voltage above 124V during my commute in order to avoid the dreaded battery light. My experience has been to slow down and coast as i aporoach a red light in hopes that I don't have to make a full stop. For a "stale green" light, I've been playing it more conservatively, since more likely than not that light will change yellow then red.

I'm hoping that lower speeds and better charging routines will help me regain some more voltage, but in the meantime going slow and constant seems to please the batteries the most.

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