Regenerative Breaking

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Deleted User 192

Post by Deleted User 192 »

G43FAN wrote: Tue Feb 09, 2021 4:26 pm I'm slightly confused by replies to this question. Are you saying that the ID3 will recognise a roundabout and slow down? Isn't this based on the Vehicle in front as in other vehicles with ACC?

It knows when you're coming up to a roundabout or tight bend, nothing to do with whether there are other vehicles in front of you.

Deleted User 192

Post by Deleted User 192 »

Hobbibear wrote: Tue Feb 09, 2021 5:40 pm My understanding of regeneration or should I say logic, is if in DB on the ID3 the car slows to about 3mph so you have a rolling motion and if you drive to that the power needed to increase momentum is less than if the car comes to a holt, as you will use more battery power to start from a stand still than from a rolling motion and that’s a better system than the EVs that when using one pedal driving that comes to a stop.

I think you're right - it's generally more efficient to coast and keep the car moving than to stop it completely.
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Post by Daveion »

G43FAN digital scott28tt
I experimented a bit today and found I get auto regen braking when approaching bends and roundabouts without ACC activated. I also get the regen braking from the pedal so now find general around town driving suits me better in D.
The auto braking must surely be in other braking settings like road recognition. I didn't have time to look further today.
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Post by simonrg »

scott28tt wrote: Tue Feb 09, 2021 6:27 pm
Hobbibear wrote: Tue Feb 09, 2021 5:40 pm My understanding of regeneration or should I say logic, is if in DB on the ID3 the car slows to about 3mph so you have a rolling motion and if you drive to that the power needed to increase momentum is less than if the car comes to a holt, as you will use more battery power to start from a stand still than from a rolling motion and that’s a better system than the EVs that when using one pedal driving that comes to a stop.

I think you're right - it's generally more efficient to coast and keep the car moving than to stop it completely.
This might be obvious, but ...
It's not just stopping which is less efficient than coasting, but any regenerative slowing down.
Driving with mechanical braking is less efficient than regeneration which will be less efficient than coasting.
Regeneration can only recover 60-80% of the energy used to get the car to speed.
ICE cars are different from EVs, in an ICE car starting from stopped is considerably less efficient than rolling, in an EV this is not the case.
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Post by hwhbev »

I think that the way you drive is the most significant factor in energy efficiency. The car whose driver has a heavy right foot (hard acceleration, hard braking) is going to have much greater energy usage than the light-footed driver who accelerates slowly, is thinking ahead all the time, lets the vehicle slow down gradually using air/wheel resistance as much as possible, etc.

The question I have is whether there is any significant difference between D and B for the light-footed driver? Set to B, the light-footed driver can still get the car to ‘coast’ by not taking their foot completely off the pedal. If they need to brake then taking their foot off the pedal in B mode is the same as getting some regen from pressing the brake pedal when in D mode. So is there any real difference between D and B for Mr/Mrs Light-Foot?
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Post by Daveion »

Im with you hwhbev. I think D suits the light foot better and makes for a better drive.
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Post by Daveion »

I looked further into my auto braking today and confirmed it wasnt just a Senior moment!
The ACC was deactivated but the car was still slowing at bends and rondabouts etc. There was a green illuminated symbol of lanes in the bottom right of the inactive ACC screen. I was able to switch this on and off using the mode. With it on it auto brakes. With it off it doesn't. I looked in the manual later and concluded I must have Eco Assistant activated. This feature is overridden if ACC is active or you are in B rather than D.
I have only very recently started driving in D so never noticed it until now.
Its page 27 and 28 in the manual.
Every time I think I get it I realise:
The more you know
The more you know
The more you know you dont know.
Its a long learning curve that hopefully doesnt reset again with updated SW.
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G43FAN

Post by G43FAN »

I don't have any real life experience of driving EVs to draw on, my car has arrived at the dealers and all being well I will pick it up in March, but reading a lot of info and watching videos plus adding a bit of school level physics.

It seems other EVs have a lever or switch which you adjust to increase or decrease the regeneration and at one extreme this allows the much talked about one pedal driving.
VW seem to have approached this by just using the brake pedal to provide this. The majority of the initial pressure on the pedal adjusts the amount of regeneration and the mechanical braking only takes over if the need to stop cannot be provided by regenerative braking alone.
So from an energy in energy out POV does the regeneration increase with pressure ( I assume it does) at which point the question is where is the balance between long slow braking (lower regeneration amount for longer) over greater pressure and therefore (I think, if I understand this at all) higher input but for a shorter time.

Obviously constant speed with as little braking and accelerating as possible would be the highest efficiency..
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Post by gailjon »

Video here shows the difference:



It is from Marcus EV
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Deleted User 192

Post by Deleted User 192 »

G43FAN wrote: Thu Feb 11, 2021 8:45 am The majority of the initial pressure on the pedal adjusts the amount of regeneration and the mechanical braking only takes over if the need to stop cannot be provided by regenerative braking alone.

So from an energy in energy out POV does the regeneration increase with pressure ( I assume it does) at which point the question is where is the balance between long slow braking (lower regeneration amount for longer) over greater pressure and therefore (I think, if I understand this at all) higher input but for a shorter time.

Obviously constant speed with as little braking and accelerating as possible would be the highest efficiency..

I think that's a good summary of how it works from my understanding and experience in the car.
G43FAN

Post by G43FAN »

gailjon wrote: Thu Feb 11, 2021 8:57 am Video here shows the difference:
That's quite enlightening.. The ACC on my Tiguan only picks up on the car in front and steering input as far as I have ever noticed. I didn't realise the ID3 would identify things like roundabouts.

With regards to the video, the comment about where or why you would use B, I live in a hilly rural area and there are a lot of journeys where I am braking to keep within a 30 limit. Potentially would B be more useful in such an environment or would limiting the speed via Cruise control in D have the same effect anyway?

It's going to be an interesting learning curve.
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Post by Deleted User 192 »

G43FAN wrote: Thu Feb 11, 2021 1:31 pm I live in a hilly rural area and there are a lot of journeys where I am braking to keep within a 30 limit. Potentially would B be more useful in such an environment or would limiting the speed via Cruise control in D have the same effect anyway?

That would be a good use case for B OR using ACC with D - if you need to keep speed to a limit the latter is probably less to worry about.

Many of my journeys (at the moment!) are on local town roads, some with speed bumps or stop/start traffic - I use B for those, but D (with or without ACC) for other journeys.
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Post by Daveion »

gailjon wrote: Thu Feb 11, 2021 8:57 am Video here shows the difference:



It is from Marcus EV
The video was useful. I can hear experienced EV owners bemoaning the discussion here promoting D rather than B and the joys of one pedal driving but maybe VW have pulled something off that was missing in other vehicles. The accelerator pedal is for acceleration and maintaing velocity.
The brake pedal is for braking whether that comes via regeneration or mechanical braking.
I am enjoying the drive in D and dont want to start slowing the second the accelerator pedal is lifted.
The added benefit of regen braking in the SW with regard to road layouts, speed limits, cars in front etc is something I want to understand more but for the moment Im enjoying the set up this way.
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Post by simonrg »

Daveion wrote: Thu Feb 11, 2021 4:10 pm The video was useful. I can hear experienced EV owners bemoaning the discussion here promoting D rather than B and the joys of one pedal driving but maybe VW have pulled something off that was missing in other vehicles. The accelerator pedal is for acceleration and maintaining velocity.
The brake pedal is for braking whether that comes via regeneration or mechanical braking.
I am enjoying the drive in D and don't want to start slowing the second the accelerator pedal is lifted.
The added benefit of regen braking in the SW with regard to road layouts, speed limits, cars in front etc is something I want to understand more but for the moment Im enjoying the set up this way.
When it behaves itself, I like the 0 pedal driving that the ID.3 is capable of.
Set ACC and just steer - car slows down for corners, roundabout, cars in front, coming up to junctions etc..
Just have foot ready in case need to manually intervene or come to a complete stop.
Possibly slows down a bit too much for roundabouts and accelerates a little too quickly when speed limit changes, but pretty impressive.
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Post by OllyExeterID3 »

Having played around, I can agree that 'D' mode and ACC are incredibly efficient for many longer journeys/ring roads and areas where it is beneficial to maintain speed rather than have to keep accelerating from too much regen.

For me, I still use 'B' mode lots in our corner of rural Devon - mainly due to narrow country lanes and 20% gradients that mean having the 'safety blanket' of immediate deceleration is incredibly useful for reaction time and ease. Saying this, using D mode through bends and winding lanes is quickly becoming my favourite way of driving - in good conditions it is unparalleled in ensuring you only decelerate when needed rather than unnecessarily. That is an unexpected bonus that is a world away from the severe one-pedal driving of our i3.
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