Beating Cruise for Economy? - Renault Z.E. Forum
 
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post #1 of 7 (permalink) Old 04-17-2014, 04:47 AM Thread Starter
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Beating Cruise for Economy?

Strange thing, but last night I set my cruise at 54 mph and thought that this would improve my range over normal (ie me) driving. But keeping a close eye on the remaining range, the miles were disappearing at a fair old rate. I thought hang on a minute I could do better than that myself - and - wait for it, sure enough I did. Perhaps it's better to have a human operated car for economy after all? I guess we can judge when to lift off in certain driving conditions, hills, corners etc a bit better than we thought. Either that or my cruise has a heavy right foot. Any one else been experiencing this, though I have no actual numbers to prove it? Maybe something to do with a continuous draw of power at that speed? Odd.
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post #2 of 7 (permalink) Old 04-17-2014, 05:06 AM
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RE: Beating Cruise for Economy?

When I turn cruise control on, even if I am only a couple MPH from where I need to be I can feel the acceleration up to cruise, something I do not notice when in manual control.

Not very scientific but I have the feeling that cruise control does eat into your miles. I did a return journey the other day that was stretching the range limit. I thought to eck out the range I would where possible use cruise control, it did not stay on long as I did notice the meter dropping more quickly.

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post #3 of 7 (permalink) Old 04-17-2014, 05:09 AM
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RE: Beating Cruise for Economy?

In general, cruise can be quite good for economy but if you want to get the best on an ICE car its usually best to let the car speed up on descents and slow on ascents, rather than trying to maintain a constant speed.

IIRC "resume" mode on the Fluence ZE's cruise results in far harder acceleration than I would normally use to gather speed again after, say, a roundabout, resulting in readings of upto 45kW - I would never hit that figure when driving with an eye to range.
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post #4 of 7 (permalink) Old 04-17-2014, 07:21 AM
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RE: Beating Cruise for Economy?

As ED says.

The cruise is quite aggressive. It is annoying really because a well-designed EV would have the cruise control integrated with the power electronics. You could achieve a 'perfect' speed setting if done correctly (by setting and synchronising the motor drive frequency with the speed). Clearly they have not done that and the cruise is a separate system that sends a [inevitably slighty delayed] control signal to the accelerator circuits.

Anyhow, it is not bad, but will over/undershoot a little. As mentioned, if you go rolling up a hill with cruise on it will suddenly give you double the power before backing off. Not the ideal for economy.

Basically, if you want max economy you can set the cruise if you are on flat ground (eg. south of Rugby on the M1). If you have terrain to go up and down, forget cruise. Pick up a bit of extra speed before the grade, then hold the power steady and allow the speed to drain away. Once over the crest let the speed build up again and then roll off the power gently. Try to stay under 20kW at all times.
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post #5 of 7 (permalink) Old 04-17-2014, 09:15 AM
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RE: Beating Cruise for Economy?

Agree. I've been alarmed at the profligacy of using cruise and after a brief flirtation, felt if I lived in East Anglia it might be worthwhile, but up here where every hill is a mountain, it's just not worth even playing with.
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post #6 of 7 (permalink) Old 04-19-2014, 02:41 PM
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RE: Beating Cruise for Economy?

To my mind nothing beats a light foot and a good look ahead to judge the situation, something cruise control can't do.
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post #7 of 7 (permalink) Old 04-21-2014, 03:56 PM
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RE: Beating Cruise for Economy?

I think cruise works well if you have flat empty roads and you don't want to concentrate on driving in the most economical/range-friendly way all the time, but it should be possible to beat it the rest of the time.

It seems a pity that the cruise on the Fluence ZE is set up to act in a similar way to systems fitted to ICE cars - it might have been nice to have an EV-optimised mode or modes, permitting less aggressive acceleration, or allowing the speed to drift a bit from the level set in circumstances where this can usefully save on battery charge.
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