Regenerative Braking: beginners explanation, please

[SpikySimonW]

Please explain it to me like I’ve never owned an EV before!

I understand the one-pedal driving concept. Seems like a good idea but not one for me, at least not yet anyway.

I also get the mechanics behind regenerative braking, it’s more the selecting of 1/2/3/A that I’m asking about. Is this not simply various levels of aggressiveness towards one-pedal driving, but of course still having to use the brake pedal as doesn’t stop completely?

I suppose my question is: is it entirely driver preference (of the operation and interplay between accelerator and brake pedals), or is there an efficiency gain/loss depending on selection? As in, will similar energy recovery still occur on depressing the brake pedal - my understanding being the car still initially decelerates using the motors (akin to ramping up the “engine braking”) before applying the actual brakes - or would I be losing out on efficiency by sticking to driving slightly more old school?

TIA

 

[MG Clive]

Hello @SpikySimonW, I think you've already answered your own question really, but very simply:

Level 1 will slow you down a little bit, and put a small amount of energy back into the battery.
Level 2 will slow you down a bit more, and put a bit more energy back into the battery.
Level 3 will slow you down quite aggressively, and put even more energy back into the battery.
OPD will slow you down the quickest, and put the most energy back into the battery, while bringing you to a complete stop.

And yes, it's entirely the preference of the driver, and how it 'feels' to them when they're driving.

The car's actual brakes will hardly be used at all if you're only using the regenerative braking.

 

[mg4mc]

It should be said the levels only apply to lifting the accelerator. The first gentle part of the brake application will then increase the regen up to it's maximum before the friction brakes start being applied when the requested braking force becomes too much for regen to satisfy.

So you can use level 1, but still use the full amount of regen using the brake - you get a feel for it after a while, glancing at the regen figure helps at first.

 

[SpikySimonW]

Thanks both, very helpful to further/cement my understanding.

Suppose I might try level 3 and see how I get on, following the rationale it could maximise the amount of regenerative braking if I then get used to not using the friction brakes as much.

Though, probably better to stop overthinking it and just enjoy the car!

 

[decrep]

Suppose I might try level 3 and see how I get on, following the rationale it could maximise the amount of regenerative braking if I then get used to not using the friction brakes as much.

I think you've misunderstood.
Regen levels, don't really affect the regen/friction braking ratio.
Regen levels only adjust, the accelerator/brake pedal action.
at level 1 lifting off the go pedal, gives a regen level equivalent to ICE engine braking, then transfers regen request to the brake pedal.
As already mentioned the brake pedal has two functions. the first part of the travel invokes regen, the 2nd part of the travel applies the friction brakes.

So this all about driver feel, not about the amount of regen.

If you want an ICE car feel go for level 1, if you like just using 1 pedal to control speed, go with 3 or OPD. Not sure about level 2, you'll have to experiment and see what suits you best.

 

[Kevin Smith]

I think you've misunderstood.
Regen levels, don't really affect the regen/friction braking ratio.
Regen levels only adjust, the accelerator/brake pedal action.
at level 1 lifting off the go pedal, gives a regen level equivalent to ICE engine braking, then transfers regen request to the brake pedal.
As already mentioned the brake pedal has two functions. the first part of the travel invokes regen, the 2nd part of the travel applies the friction brakes.

So this all about driver feel, not about the amount of regen.

If you want an ICE car feel go for level 1, if you like just using 1 pedal to control speed, go with 3 or OPD. Not sure about level 2, you'll have to experiment and see what suits you best.

When you say "at level 1 lifting off the go pedal, gives a regen level equivalent to ICE engine braking", which gear do you imagine the ICE car is in? Engine braking in an ICE car will depend on which gear is selected, strongest in 1st gear and weakest in 7th(6,5,4th depending on number of gears). I would say from experience level 1 is approximately like lifting in 6th, level 2 like lifting in 4th and level 3 like lifting in 3rd. but it is more complicated than that depending more on speed, incline and so forth. Whichever regen level you set you then get to practice lifting more or less gently for the cruise or deceleration you want. If you are incredibly pedal dextrous you can hold the motor/regen % at a more or less steady 0% for a cruise.

 

[Anon70]

There are also different schools of thought on when it is best to use more or less regen. The thinking goes that more more energy you wipe off of the car the more you will need to get it back to where it was. So allowing more coasting and less regen gives better efficiency than high regen and the need to use more power to get back up to speed. That is why the A, adaptive setting should be auto adjusting based on traffic.

 

[decrep]

The thinking goes that more more energy you wipe off of the car the more you will need to get it back to where it was. So allowing more coasting and less regen gives better efficiency than high regen and the need to use more power to get back up to speed. That is why the A, adaptive setting should be auto adjusting based on traffic.

This is only true, if you have little control over your right foot!

The only reason you'd be using more regen is if you lift your foot off more than needed.
If you slow to the necessary speed, and no more, the above argument is meaningless.

OK, so I guess some people are just used to taking their foot off the go pedal and cruising when needing to slow down. If that's the way you want to drive, by all means deactivate the go pedal invoking regen..

 

[MickeyD]

Supplementary question-1,2,or 3 for ‘de-rusting’ brakes ?

 

[mg4mc]

Doesn't matter, you need to apply the brake firmly to get past all the regen, whether accelator lifting or initial gentle brake application induced.

 

[decrep]

Supplementary question-1,2,or 3 for ‘de-rusting’ brakes ?

Makes no diff, same amount of regen in all 3 cases.
You need little or no regen for derusting brakes, it's been said many times before.
no regen in reverse, at 100% SoC or in Neutral.
If you're brave you can also use accelerator and brake pedals together, (I haven't tried this yet.). Also hard braking above regen levels will do some good.

 

[mg4mc]

As soon as you press the brake, the accelerator cuts out.

 

[decrep]

As soon as you press the brake, the accelerator cuts out.

I haven't tried it but somebody here definitely said it works

 

[tsedge]

I prefer the Adaptive (A) setting, because at motorway speeds it is like an ICE car and my foot doesn't get tired holding the accelerator down far enough to maintain speed, but then at slower speeds it progressively increases to provide high regen, which is ideal for traffic.

 

[MG Clive]

I prefer the Adaptive (A) setting, because at motorway speeds it is like an ICE car and my foot doesn't get tired holding the accelerator down far enough to maintain speed, but then at slower speeds it progressively increases to provide high regen, which is ideal for traffic.

Ahh well, I don't like the adaptive, I want to know that when I lift my foot off the accelerator pedal, the car is always going to react in exactly the same way with regards to it's braking.

 

[tsedge]

Ahh well, I don't like the adaptive, I want to know that when I lift my foot off the accelerator pedal, the car is always going to react in exactly the same way with regards to it's braking.

Interesting. I find the Adaptive setting entirely predictable and haven't had any issue getting used to how it works.

 

[OriginalBigAl]

Has anyone else noticed the regen values and feel change when switching driving modes?
Start with "normal Level 3 " as default and on a flat level road and on a steady positive throttle change to "Sport level 3 " then " custom level 3 " and onto " Snow level 1 " then to "ECO level 3" , all default settings.
From custom to snow the car seems to surge slightly and feels less restrictive , going to eco there is then a slight slowing and more resistance is felt. Does this suggest that on level 3 even on a positive throttle there is always a little re-gen and resistance being produced, as a by product of that setting. Sounds wrong and counter intuitive but for now its the only explanation I can think of, otherwise a positive throttle should suggest no re-gen at all?

 

[mg4mc]

But changing the modes changes the accelerator response curve, so holding a steady position whilst changing modes is meaningless, with each regen setting you will on a different point of the curve.

 

[OriginalBigAl]

But changing the modes changes the accelerator response curve, so holding a steady position whilst changing modes is meaningless, with each regen setting you will on a different point of the curve.

That makes sense up to a point, the slight kick/surge that is felt when changing to Snow setting is strange, you would think that Snow setting would give you the most relaxed throttle response for any given throttle position, the level 1 regen default would be to stop locking the wheels on a slippery surface when releasing the throttle.
All the other modes are default level 3 and not much difference ( if any ) in a perceived difference in response when scrolling through from one to the other on a steady throttle . The only obvious slight differences is either side of Snow mode.
You would also imagine that any regen setting points on any of the curves would only be applicable when the power goes into minus figures, on plus power settings they should be non applicable?
Its not an argument , I'm just trying to understand why it does what it does.

 

[SpikySimonW]

Snow mode?