Regenerative Breaking - Explained

[Ozukus]

This is an attempt to explain the way that Regenerative Breaking works - please feel free to amend, discount, simplify or agree even!

Regenerative Breaking is engaged through the application, or release, of pressure on either the break pedal or the accelerator pedal dependent upon the manual B setting of 0-5 or the default B setting while in drive of 2. Lets start with the two extremes of 0 and 5.

With B set at "0" or "coast" mode if you

- apply pressure to the break pedal the first 15mm of pedal travel will increment the regenerative breaking through B1, B2, B3, B4 to B5 before it engages the friction breaks.

- reduce pressure on the break pedal then you will be applying friction breaks until the last 15mm of pedal travel where it will decrement the regenerative breaking from B5, B4, B3, B2 to B1 until the pedal is full disengaged.

- apply or reduce pressure to the accelerator pedal then the first or last 15mm of travel respectively will effectively be a dead zone.

With B set at "5" or "maximum regen" mode if you

- apply pressure to the accelerator pedal the first say 15mm of pedal travel will decrement the regenerative breaking through B4, B3, B2, B1 to B0 before it applies power to the electric engine.

- reduce pressure on the accelerator pedal then you will be reducing power to the electric engine until the last 15mm of pedal travel where it will increase the regenerative breaking from B1, B2, B3, B4 to B5 until the pedal is full disengaged.

- apply or reduce pressure to the break pedal then the first or last 15mm of travel respectively will effectively be a dead zone.

Now looking at the other options of 1-4 we will use B2 or standard drive mode (default B2) as an example. So if you

- apply pressure to the break pedal the first say 6mm of pedal travel will be a dead zone and next 9mm will increment the regenerative breaking through B3, B4 to B5 before it engages the friction breaks.

- reduce pressure on the break pedal then you will be applying friction breaks until the last 9mm of pedal travel where it will decrement the regenerative breaking from B5, B4 to B3 with the last 6mm being a dead zone until the pedal is full disengaged.

- apply pressure to the accelerator pedal the first say 9mm of pedal travel will be a dead zone and the next 6mm of travel will decrement the regenerative breaking through B1 to B0 before it applies power to the electric engine.

- reduce pressure on the accelerator pedal then you will be reducing power to the electric engine until the last 6mm of pedal travel where it will increment the regenerative breaking from B1 to B2 and the last 9mm being a dead zone until the pedal is full disengaged.

I have used 15mm as an example figure in order to describe the process however what I have learnt is that I can set the paddles to either B0 or B5 and use either the break pedal or accelerator pedal to establish the level of regenerative breaking that is applied.

So for motorways I can set it to B0 or Coast mode and with a light application of the break pedal can control the level of regenerative breaking that is occurring with my break lights on.

 

[Paule23]

Interesting stuff, where does this information come from?

 

[user 258]

Hi,

I agree pretty much with Ozukus and his post. My only comment is that I suspect that as soon as the brake pedal is pressed some friction braking is applied at the same time as regen braking. I think this is done either for safety (so some friction brakes are always applied) or to get a smooth transition from regen to friction. Regen braking is pretty useless at speeds below about 6mph so when slowing down it would have to transition from regen to friction as you slow. As a previous Prius driver it was possible to detect a slight change at this point, and Toyota have had 15+ years to perfect it.

Personally, I now just switch straight to B5 as I like the almost one pedal driving. I am, however, careful when using the full B5 braking to check if there are close cars behind and if so also use a little foot brake to display the brakelights.

Kind regards,
Mark

 

[Ozukus]

Interesting stuff, where does this information come from?

The information comes from this forum and from personal experience.

Here's a couple of posts that have references to regenerative breaking.

http://www.myoutlanderphev.com/forum/viewtopic.php?f=9&t=969

http://www.myoutlanderphev.com/forum/viewtopic.php?f=10&t=531

From a personal perspective it was a comment "jaapv" made in the first post that got me thinking about it and from that I decided to do some testing. Naturally this was with a semi depleted battery as with a full battery regenerative breaking will do nothing as it has nowhere to store the energy. I had two trips recently that included a very long decline as you go down the A20 or A21 so fiddled about with the paddles, accelerator and brake, which resulted in my post on how I think it works.

 

[PolishPilot]

...
Personally, I now just switch straight to B5 as I like the almost one foot driving.

Same her. One foot driving is very relaxing.
If I want to coast I just apply some gas pedal.
I have the energy flow diagram permanently displayed,
I can see easily whn I regen or coast.

Also the power gauge is a good indicator
how much the throttle should be pressed.

 

[maby]

I did try driving on B5 for a while, but I had a couple of close calls where the guy behind almost ran into the back because of the lack of brake lights, so I reverted to normal driving. Having to check behind before braking to see if there is someone close and then select whether to use the pedal or not just adds to the number of distractions. I just use B5 on long hill descents now.

 

[user 258]

I did try driving on B5 for a while, but I had a couple of close calls where the guy behind almost ran into the back because of the lack of brake lights, so I reverted to normal driving. Having to check behind before braking to see if there is someone close and then select whether to use the pedal or not just adds to the number of distractions. I just use B5 on long hill descents now.

Hi,

Yes, I accept that point. I've just got (maybe was always) into the habit of knowing if anything was behind me at all times anyway so it doesn't really add an extra step for me anyway.

Kind regards,
Mark

 

[jaapv]

Driving on B5 does not add anything for me, the feel of the car, to me, is just right at the standard setting and very similar to me previous car on compression braking. Nor did I discover any benefits in regenerating electricity, so I would only use it on hills.

 

[anko]

Nor did I discover any benefits in regenerating electricity, so I would only use it on hills.

How can you "not regenerate electricity"? With any B setting, even B0, you will regenerate electricity when you operate the break pedal.

 

[user 258]

Nor did I discover any benefits in regenerating electricity, so I would only use it on hills.

How can you "not regenerate electricity"? With any B setting, even B0, you will regenerate electricity when you operate the break pedal.

Hi,

I think he means using B5 doesn't generate more energy than using B2 and pressing the brake pedal somewhat since pressing the brake pedal will increase the amount of energy captured.

Kind regards,
Mark

 

[jaapv]

Nor did I discover any benefits in regenerating electricity, so I would only use it on hills.

How can you "not regenerate electricity"? With any B setting, even B0, you will regenerate electricity when you operate the break pedal.

Because it will not generate more by setting a paddle. The regeneration is governed by the kinetic energy of the car. I think we are talking at cross-purposes here. I meant there is no extra benefit to be gained by using the paddles instead of the brake pedal.

 

[anko]

I meant there is no extra benefit to be gained by using the paddles instead of the brake pedal.

If that's what you meant, I agree with you. Choosing any of the B levels is a matter of taste.

 

[Ozukus]

I meant there is no extra benefit to be gained by using the paddles instead of the brake pedal.

If that's what you meant, I agree with you. Choosing any of the B levels is a matter of taste.

This was part of what my post was trying to explain, that the regenerative breaking is actually controlled by the brake and accelerator pedals and the B setting just determines how that is applied.

- If B0 is set then regenerative breaking is controlled through the brake pedal

- If B5 is set then regenerative breaking is controlled through the accelerator pedal

- Any other setting then it is a combination of both the brake and accelerator pedals

I think that the paddles in most cases are really just a novelty and there are only specific circumstances where they become really beneficial, by example.

- For steep downhills setting at B5 will provide a lot of regen
- For any reasonable uphill setting at B0 will ensure that you maximise coast if you do have to take your foot off the accelerator and not engage the equivalent of an engine brake as the amount you will regenerate will not replace what you use to get back up to speed

To that end I would agree with JAAPV that only under specific circumstances you may use the paddles to increase your EV range, otherwise you are using them for the novelty of paddle braking control instead of using the accelerator and brake pedal as described earlier.

 

[maby]

I do think that the paddles serve a purpose for hill descents - they apply a more controlled level of braking than can be achieved with the pedal.

 

[jaapv]

I would agree with this analysis. It also implies that it is reasonable that the brake lights do not come on. You do not want to blind the guy behind you on a descent at night. It would be quite nervous for the traffic behind you if the lights come on each time you lift your foot off the accelerator in flat driving as well.

If the paddles are left alone in the vast majority of circumstances (depending where one drives the car of course) it will behave like any other car and not endanger traffic by sudden braking without the brake lights, whilst still regenerating the same amount of electricity.
To build the car to drive like a conventional car was one of the design targets.

 

[SMB]

Some good info here. Makes me think there should be a compulsory 1 day training course when you buy the PHEV in order to teach you how the bl00dy thing should be driven! The dealership seem pretty clueless.

 

[Ozukus]

When I took the car for a first test drive at Mitsubishi Bromley the young lad who took us out was excellent and explained that he had received special training. The dealership then transferred to Mitsubishi Shirley under the Masters Group and the whole lot there are absolutely clueless.

I think there is more meaningful information on this site that has been garnered from actual use than anything that the dealerships could provide.

 

[Marksuk]

So just to recap....
The brake pedal activates regenerative braking in certain circumstances.
The brake discs etc are then doing little work because of this. You would think the discs would be smaller if this was the case.
It makes you wonder why it has got brakes/discs at all or is that a legal requirement.

Is all this actually real information or just what seems logical-ish, personally I thought the brakes would work just as normal as in any car and this brake mode of operation seems a bit OTT. I would think certain features like ABS and traction contol would be a bit of a nightmare if this is the case. If the system is so advanced then why does it just have a mechnical and not an electric handbrake.
I would think braking and regeneration are two independent different systems and are not really interlinked at all TBH. I have personally have no proof of this otherwise.

 

[anko]

It makes you wonder why it has got brakes/discs at all or is that a legal requirement.

Breaking capacity under B5 is 1,0 m/s2. This may already result in 40 kW or more power being returned to the battery. But minimal braking capacity for a car is 5.8 m/s2 by law (at least in the Netherlands). No way you can provide that amount of stopping power by means of regenerative breaking without blowing your battery to kingdom come.

And let not forget, when the battery is full, there is no regenerative breaking. So, you will still need the normal amount of conventional stopping capacity.

 

[Ozukus]

"The brake pedal activates regenerative braking in certain circumstances."

Correct and so does the accelerator pedal, explained in initial post.

"The brake discs etc are then doing little work because of this. You would think the discs would be smaller if this was the case."

The regenerative breaking is similar to engine breaking and it won't really stop the car effectively. You still need the brakes to be like normal brakes as it has to stop 2 tonnes of vehicle. It's just the same as a normal car that uses both engine breaking and discs to stop the car.

Also with a full battery regenerative braking does absolutely nothing so you definitely need brakes to stop the car with a full battery.

"Is all this actually real information or just what seems logical-ish"

Based on usage and testing I believe the information I posted is correct. you can also test it yourself, find a reasonably long downhill, set the B mode to B0 or coast and make sure your battery has a level of depletion. As you are going down the hill just very lightly touch the brake and you will see the energy flow go from the wheels to the battery and the needle in the power regen will show a level of regen. Then add slightly more pressure to the brake pedal and you will see the need in the power regen area show an increased level of regen. as you lift/apply/lift/apply pressure to the brake pedal you will see that you can control the amount of regen being applied.

It's also apparent when the battery is full as the initial application of pressure to the brake pedal does nothing at all until it kicks in the friction brakes and lifting your foot off the accelerator it feels like its coasting, whereas when the battery is depleted lifting your foot off the accelerator gives you the feeling of engine braking and when you apply pressure to the brake pedal you get an immediate feeling that you are braking the car, when in effect you are just increasing the B level through to 5 before the friction brakes kick in.