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Discussion Starter · #1 ·
A conversation on another thread, and some driving today made me think I should double check I understand some of the basics of EV driving. I've had an EV nearly a year now so I should perhaps have double checked this earlier, but better late than never! I've attached a picture from the dashboard of my e-Golf to illustrate my questions.

First question is, am I right that if the gauge reads exactly what is shown in the picture while my vehicle is moving then I am coasting? And that this is true whether I have regen turned on or not?

If so, am I also right that if I'm on a motorway on cruise control, if the gauge is either on 0 as shown, or somewhere up in the blue bit then I am driving with just as much efficiency at that exact moment in time as I would be if I was setting the speed myself with the pedal?

However, if I'm on cruise control and the needle moves into the green bit (so, I'm on a downhill slope), I am then at that moment in time driving less efficiently than if I turned off cruise control, turned off regen, and let it coast building speed down the slope?

If so, the most efficient way to drive on the motorway if you did want to in the main use cruise control is to keep an eye on that gauge, and as soon as it creeps into the green bit cancel the cruise control (with regen off) and let it coast and build up speed. Then, once the speed slows down again to your cruise control set point (so, you're no longer going downhill) re-engage the cruise control?

Thanks!

(And yes... I know I need to dust my dashboard thank you very much! :LOL: )

137571
 

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OP, I think you are confusing yourself with too many considerations.

My 2c:
  • hand at 0 is "coasting", so no energy use;
  • hand in blue and above, using energy (battery) to move;
  • hand in green, recuperating energy to the battery;

Anything beyond that is "use ACC" as much as you can. You will not be able to drive the car more efficiently, although some people prefer to be in control. I say that with the assumption that the speed is fixed, i.e. even if you manually control speed you can't increase or reduce it.
 

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I’d say you’re correct it’s going to be more efficient to coast downhill than use regen. Which is fine if you’re well under the speed limit to start with and the hill isn’t too steep etc etc. If you need to keep it under the speed limit then using regen to do that is obvs better than using friction brakes. On a longish s sedate motorway drive I did this a bit on some steep hills, setting the regen to 0 and cancelling cruise. Let my speed pick up downhill and then resume cruise once my speed is back at the set point.
 

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Discussion Starter · #5 ·
OP, I think you are confusing yourself with too many considerations.

My 2c:
  • hand at 0 is "coasting", so no energy use;
  • hand in blue and above, using energy (battery) to move;
  • hand in green, recuperating energy to the battery;

Anything beyond that is "use ACC" as much as you can. You will not be able to drive the car more efficiently, although some people prefer to be in control. I say that with the assumption that the speed is fixed, i.e. even if you manually control speed you can't increase or reduce it.
Thanks! I probably worded it confusingly. What I'm getting at is, I've heard that not using cruise control and driving using the pedals with regen off is most efficient on motorways because you can,
  1. Allow your speed to decrease a bit when going uphill - so you're not using the battery to 'power up' hills,
  2. Allow your speed to maintain or increase a bit when going downhill by coasting.
But I like to use cruise control, so I'm wondering whether there is a middle ground whereby you leave the cruise on most of the time, so still take the efficiency hit of it 'powering up' hills, but switch the cruise control off temporarily and coast down hills when you get to them?

I’d say you’re correct it’s going to be more efficient to coast downhill than use regen. Which is fine if you’re well under the speed limit to start with and the hill isn’t too steep etc etc. If you need to keep it under the speed limit then using regen to do that is obvs better than using friction brakes. On a longish s sedate motorway drive I did this a bit on some steep hills, setting the regen to 0 and cancelling cruise. Let my speed pick up downhill and then resume cruise once my speed is back at the set point.
Ah! Sounds like you do what I'm describing then. You mostly keep your cruise on, but turn it off temporarily and coast when you come to the downhill bits?
 

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If so, the most efficient way to drive on the motorway if you did want to in the main use cruise control is to keep an eye on that gauge, and as soon as it creeps into the green bit cancel the cruise control (with regen off) and let it coast and build up speed. Then, once the speed slows down again to your cruise control set point (so, you're no longer going downhill) re-engage the cruise control?
Yes. The reason is that although regen captures energy, much better than friction brakes, it's not as efficient as coasting downhill and storing that extra energy as kinetic energy.

But there is an easier way to do this:
  • keep an eye on the gauge
  • if it creeps into regen (green) bit, lightly apply pressure on the accelerator to tell the car to speed up. Maintain the needle to be around 0
  • slowly back off the accelerator as the road levels, try to maintain needle around 0 and your speed will slow down to CC speed and CC takes over automatically
Easy :) Most modern cars have overtaking feature where it allows you to override cruise control by speeding up and automatically resumes to prevent you from slowing too much.

But don't sweat over it and don't stare at the needle. Drive safely.
 

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Discussion Starter · #7 ·
Yes. The reason is that although regen captures energy, much better than friction brakes, it's not as efficient as coasting downhill and storing that extra energy as kinetic energy.

But there is an easier way to do this:
  • keep an eye on the gauge
  • if it creeps into regen (green) bit, lightly apply pressure on the accelerator to tell the car to speed up. Maintain the needle to be around 0
  • slowly back off the accelerator as the road levels, try to maintain needle around 0 and your speed will slow down to CC speed and CC takes over automatically
Easy :) Most modern cars have overtaking feature where it allows you to override cruise control by speeding up and automatically resumes to prevent you from slowing too much.

But don't sweat over it and don't stare at the needle. Drive safely.
Oh, of course! Yes, that makes much more sense than switching it off and on again. Ok, I think I'll try to do this from now on. I know I could drive most efficiently by switching the CC off totally so that I'm also allowing my speed to decrease a bit going up steep hills, but that's too much hassle for my liking. But just allowing the car to pick up speed by using your method when going downhill, and when doing so wouldn't annoy other drivers or break the law doesn't sound too onerous and might get me a few extra miles over a long journey.

Thanks!
 

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  1. Allow your speed to decrease a bit when going uphill - so you're not using the battery to 'power up' hills,
  2. Allow your speed to maintain or increase a bit when going downhill by coasting.
That is why I said "fixed speed". If you want to control it yourself, those two points are all good.
 

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I’d say you’re correct it’s going to be more efficient to coast downhill than use regen. Which is fine if you’re well under the speed limit to start with and the hill isn’t too steep etc etc. If you need to keep it under the speed limit then using regen to do that is obvs better than using friction brakes. On a longish s sedate motorway drive I did this a bit on some steep hills, setting the regen to 0 and cancelling cruise. Let my speed pick up downhill and then resume cruise once my speed is back at the set point.
Interesting debate isn't it...by speeding up, more energy is going into noise, heat etc overcoming air resistance. That will increase as the square of speed in general. If regen efficiency is broadly similar across the speed range then I'd suggest it ought to be more efficient to capture excess energy using regen rather than burn it as heat. If you want the excess speed, then of course that's a different discussion.
 
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Going downhill on motorways has various scenarios which include,
HGV generally speed up downhill
Modern cars on CC / ACC stay at constant speed
Some drivers just vary.

I normally switch off ACC downhill, speed up and then re-engage ACC when returned to my established speed.
 

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It's not totally clear cut. It really depends on how fast you are going, how steep the hills are and how strong the wind is. I suspect that ACC is unnecessarily fast to accelerate and wastes a little energy by slowing you down rather than coasting. However, significant speed increase by coasting would also waste energy.

There will be an optimal middle ground which would require constant variation in speed that ACC is designed to avoid. Full manual control is needed to achieve maximum efficiency, but that doesn't mean always coasting as much as possible.
 

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Throwing this out there as an alternative - do you have a speed limiter? On the GTE, it'll coast until it hits the limit, then regen to hold the limit. You have to hold the accelerator down yourself (but not with much finesse, as the limiter will control your speed), but you can ease off when you reach an uphill to slow down a bit and use a little less energy to reach the top. It's kind of a happy medium between full control and ACC. This is becoming my preferred driving style for the country roads. For motorways, I still tend to be lazy and use ACC.
 

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Discussion Starter · #13 ·
Going downhill on motorways has various scenarios which include,
HGV generally speed up downhill
Modern cars on CC / ACC stay at constant speed
Some drivers just vary.

I normally switch off ACC downhill, speed up and then re-engage ACC when returned to my established speed.
I will probably speed up downhill now using wyx087’s technique, unless doing so would force me to overtake a vehicle that has just overtaken me, because I feel like that is just annoying to them as they’ll have to overtake me again a second time when I slow back down to my set speed.

Throwing this out there as an alternative - do you have a speed limiter? On the GTE, it'll coast until it hits the limit, then regen to hold the limit. You have to hold the accelerator down yourself (but not with much finesse, as the limiter will control your speed), but you can ease off when you reach an uphill to slow down a bit and use a little less energy to reach the top. It's kind of a happy medium between full control and ACC. This is becoming my preferred driving style for the country roads. For motorways, I still tend to be lazy and use ACC.
I’m not sure, but that’s basically the exact opposite of what I’m wondering about doing anyway isn’t it? As in, whether I should accelerate on the downhill bits and maintain speed on the other bits. That would have me decelerate on the uphill bits and maintain speed on the other bits 😃 I think I want to continue to use ACC in the main... I figure I paid for a car with snazzy toys so I should use them! But more importantly, I do find it makes motorway driving more relaxing most of the time
 

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Throwing this out there as an alternative - do you have a speed limiter? On the GTE, it'll coast until it hits the limit, then regen to hold the limit. You have to hold the accelerator down yourself (but not with much finesse, as the limiter will control your speed), but you can ease off when you reach an uphill to slow down a bit and use a little less energy to reach the top. It's kind of a happy medium between full control and ACC. This is becoming my preferred driving style for the country roads. For motorways, I still tend to be lazy and use ACC.
I think I'm likely to adopt this technique. Not least because the MG5 won't have ACC but will have a speed limiter. I can then pretend that I prefer not to have ACC because it's less efficient.
 

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I’m not sure, but that’s basically the exact opposite of what I’m wondering about doing anyway isn’t it? As in, whether I should accelerate on the downhill bits and maintain speed on the other bits.
It let's you speed up on the downhill within the limits of the law (or more specifically, within the limits of the limit that you set on the limiter), ease up on the uphill if you want, and otherwise maintain speed with minimal effort. Basically it lets you ease up on the uphill without having to switch something off.
 

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I believe the MGS does not use regen when on CC and going downhill, as the mfrs used a CC module out of the parts bin that didn't understand regen, so instead it uses the discs to prevent speed increasing! Has this been fixed on the MG5 ?
 

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Discussion Starter · #17 ·
It let's you speed up on the downhill within the limits of the law (or more specifically, within the limits of the limit that you set on the limiter), ease up on the uphill if you want, and otherwise maintain speed with minimal effort. Basically it lets you ease up on the uphill without having to switch something off.
Thanks, but I like using the adaptive cruise control most of the time, so I think I'll stick with that. This was more an exercise in using the coasting more on long trips than abandoning ACC altogether.
 

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If i can i coast down hill and before going up and loosing speed i apply power to get me up the next hill. At most the power applied is the max that can be applied in the Eco+ mode (equal to about 1.8-1.9 on the Golf gauge) without causing kickdown. If this results in speed reduction so be it. If no hill coming allow speed to decay down to desired cruise speed before engaging cruise and perhaps limiting speed to 60mph if still in Eco+.
 

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I believe the MGS does not use regen when on CC and going downhill, as the mfrs used a CC module out of the parts bin that didn't understand regen, so instead it uses the discs to prevent speed increasing! Has this been fixed on the MG5 ?
Well you could call it fixed... They removed Adaptive Cruise Control altogether. So no automatic application of the friction brakes at the expense of no automatic slowing at all. It's a great improvement in my opinion.
 
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