Breaking & recuperation

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RAL7004
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Breaking & recuperation

Post by RAL7004 » Sat Feb 08, 2020 4:20 pm

7FDA2892-8442-453F-B6CE-50336621FDE0.jpeg

Found this and wonder how recuperation works in „normal“ (I.e. NOT one pedal) driving.
I understand that there are four levels. Does this mean that if I break in “level 4” 0.1G deceleration will be achieved via the motor/recuperation before the mechanical breaks will step in - in “level 1” after 0.01 G ?

Joolsdc
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Re: Breaking & recuperation

Post by Joolsdc » Sat Feb 08, 2020 9:06 pm

The way I thought it was explained: 3-4 levels of brake recuperation controlled by paddles on steering wheel. This only uses the motor in reverse to charge batteries
Press the one peddle button drive button on centre console. Thus had 3-4 levels as well. But thus time the brakes will also be applied to come to complete stop

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rickwookie
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Re: Breaking & recuperation

Post by rickwookie » Sun Feb 09, 2020 11:14 am

Yes the brake will only be applied, without you actually pressing the brake peddle, in one-peddle mode (with the exception of the low-speed traffic collision avoidance, and perhaps adaptive cruise emergency?). Even then I think the break is only applied the bring the car fully stationary after it has slowed. In any other mode, it’s simply regen slowing you down, the aggression of which which can be selected using the paddles on the steering wheel.

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RAL7004
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Re: Breaking & recuperation

Post by RAL7004 » Sun Feb 09, 2020 11:52 am

OK - what I would like to know is the following:
Let‘s assume we drive in „normal“ mode, 0.1 G recuperation.
When the throttle/accelerator pedal is released we will glide (I hope).
When pushing the break pedal to a certain extent recuperation with 0.1 G will start and we will decelerate.
If we push harder the mechanical breaks will kick additionally in to further decelerate the car.

Btw: if this is how it works why recuperation isn’t depending on the extent of pushing the brake pedal?

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keithr
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Re: Breaking & recuperation

Post by keithr » Sun Feb 09, 2020 6:20 pm

I don't speak that language, but I understand it to be saying that in normal 'D' mode you can choose between 0.04, 0.06, 0.08 or 0.10g of regenerative braking when you take your foot completely off the accelerator pedal. In the one-pedal mode you can choose between 0.10, 0.14 or 0.18g of regenerative braking. So the nearest you can get to coasting is in D mode, lowest setting, i.e. 0.04g. The only way to really coast, apart from balancing it on the accelerator pedal, would be to put it into 'N' - neutral - but I suspect that might not be recommended.

In my Nissand LEAF, and I assume it wil be the same in the Honda e, when you apply the brake pedal it will always give preference to regenerative braking and use as much regen. as possible before then applying the brakes (to optimise the range). So if you were in 0.04g mode and pressed on the brake pedal sufficently to give 0.3g of braking, then it would use the maximum of 0.18g regen. (assuming you were travelling fast enough to get 0.18g regen.) and 0.12g from the brakes.

For perspective, I remember reading an Autocar road test of the car I had back in 90's, a Vauxhall Astra GTE 2.0 16V, which they said had good brakes and measured it under maximum braking as giving 1.1g of retardation.

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Re: Breaking & recuperation

Post by rickwookie » Thu Feb 13, 2020 10:29 pm

I assume those regen levels are what gets applied when you come off the throttle. It would always make sense for the car to try to use as much regen as possible when you actually press the brake, irrespective of what level you’ve set, before actually applying the friction brakes.

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RAL7004
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Re: Breaking & recuperation

Post by RAL7004 » Fri Feb 14, 2020 7:11 am

I assume (and hope) it's different:
The three recuperation levels (on the right of the picture) will be applied during "one pedal diving" – when you come off the throttle.
In "normal" mode we will glide (or whatever you call it in English – "segeln" in German) when the throttle/accelerator pedal is released.
When pushing the break pedal recuperation will start according to the level you have chosen (0.04, 0.06, 0.08, or 0.1 G). Breaking via the electric motor will only work to a certain degree – thereafter, the mechanical breaks will kick in.

Have a look at this video from Volkswagen and their solution for the current e-Golf:


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keithr
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Re: Breaking & recuperation

Post by keithr » Fri Feb 14, 2020 2:27 pm

RAL7004 wrote:
Fri Feb 14, 2020 7:11 am
I assume (and hope) it's different:
The three recuperation levels (on the right of the picture) will be applied during "one pedal diving" – when you come off the throttle.
In "normal" mode we will glide (or whatever you call it in English – "segeln" in German) when the throttle/accelerator pedal is released.
When pushing the break pedal recuperation will start according to the level you have chosen (0.04, 0.06, 0.08, or 0.1 G). Breaking via the electric motor will only work to a certain degree – thereafter, the mechanical breaks will kick in.

Have a look at this video from Volkswagen and their solution for the current e-Golf:
That sounds identical to the Nissan LEAF that I have, and indeed most/all other electric cars that I've read about. It has a BMS (Brake Management System) that controls the brakes (braking "by wire", rather than manual braking). I believe it uses an electric motor or solenoid to control the brake master cyclinder, all computer controlled, of course. So when you apply pressure to the brake pedal it is programmed to give you the level of braking you would expect from a conventional manual brake pedal, but it will be using as much regenerative braking as possible (regardless of which regenerative braking mode you have selected) and then additionally apply the brakes to give you the retardation you want/expect. When the battery is fully charged there will not be any regeneration available (you can't put charge into a battery if it is fully charged!) so it will be applying the brakes harder. (In normal D mode there will be less, or no, engine braking effect when you back off on the accelerator pedal with a fully charged battery, but in one pedal mode it will automatically apply the brakes to simulate the same level of slowing as when the battery is not fully charged). Likewise if the battery is too hot or cold then it will use less regenerative braking to prevent damaging the battery, so again in that case it will apply more brakes, but it always tries to make the brake pedal response seem the same to the driver, whatever is the mix of regen. and brakes.

Because the brakes on an electric car are used less (due to harnessing regenerative braking) it will occaionally not use regenerative braking at all, and just use the brakes, in order to help prevent the brakes from seizing up. When I'm using e-pedal, i.e. one pedal driving, my LEAF occasionally chooses to do that when I'm slowing down to stop at a junction at the bottom of a steep hill, so it takes the opportunity to apply the brakes harder than normal - quite clever. :)

BTW, many reviewers seem to think that strong regenerative braking enables you to have one pedal driving, but it doesn't. It's only truly one pedal driving when the car will also automatically apply the brakes to bring the car to a complete halt when you simply take your foot off the accelerator pedal. If you have to use the brake pedal to bring the car to a halt then it isn't one pedal driving. The Nissan LEAF was the first car to have one pedal driving, which Nissan calls e-pedal. The Honda e also has it (but it hasn't given it a name!).

So when you don't use the brake pedal, but simply back off on the accelerator pedal, it will give you increasing regenerative braking from virtually none up to the maximum when you take your foot completly off the pedal, with the maximum depending on the regen. mode you've selected. Therefore the nearest you can get to gliding , or coasting, i.e. the car just rolling under it's momentum but with no driving or braking force (like when you stop pedalling on a bicycle) is in D mode with the maximum of 0.04g regenerative braking selected. However, often when I'm in e-pedal mode (one pedal driving), I can coast/glide by simply backing off the appropriate amount on the accelerator pedal, i.e. so that the real-time display of power consumption or regenerative breaking is displaying no power being consumed or generated.

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keithr
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Re: Breaking & recuperation

Post by keithr » Fri Feb 14, 2020 2:48 pm

rickwookie wrote:
Thu Feb 13, 2020 10:29 pm
I assume those regen levels are what gets applied when you come off the throttle.

Actually it doesn't have a throttle! ;) Only petrol powered internal combustion engined cars have a throttle (to throttle the amount of air entering the engine). Diesel engined cars and electric cars don't have a throttle.

Sorry, I couldn't resist ! :geek: I'm sure it was just force of habit!

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Re: Breaking & recuperation

Post by rickwookie » Sat Feb 15, 2020 2:02 pm

keithr wrote:
Fri Feb 14, 2020 2:48 pm
rickwookie wrote:
Thu Feb 13, 2020 10:29 pm
I assume those regen levels are what gets applied when you come off the throttle.

Actually it doesn't have a throttle! ;) Only petrol powered internal combustion engined cars have a throttle (to throttle the amount of air entering the engine). Diesel engined cars and electric cars don't have a throttle.

Sorry, I couldn't resist ! :geek: I'm sure it was just force of habit!
Actually, as an alternative to typing "accelerator pedal", it's just quicker (the 'quicker' pedal is another alternative of course). Easiest of all to type would be "gas", but I have some standards. :lol:

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