Regeneration Boost Switch

[Empty Sea]

When the Regeneration Boost switch is turned on, does anyone know if the brake lights come on when you take your foot off the accelerator pedal - i.e. to allow the car to slow down?

[philip42h]

I don't know, of course, but I rather doubt it ... lifting one's foot off the accelerator causes any car to slow down but no one expects the brake lights to come on; brake lights coming on, even with a tad extra regenerative braking, is likely to cause 'panic' amongst the drivers following ... 😉

[swoop5511]

there is no official EU/UK law, but a general UN directive that most manufacturers adhere too

Quote

The law that defines whether brake lights come on for cars braking with regenerative braking is the UN rules. The law changed sometime around 2015/2016. Before then, it was actually prohibited to have brake lights illuminated by regen with no brake pedal input¹. Electric regenerative braking systems as defined in paragraph 2.17., which produce a retarding force upon release of the accelerator control, may only generate the signal mentioned above at decelerations above 1.3 m/s². However, if the signal has been generated, the signal shall be de-energized when the vehicle speed exceeds 5 km/h¹

 

[Cyker]

It is likely - Most of the 'one-pedal driving' style modes in EVs trigger the brake lights when you lift off past a certain point, for safety reasons.

It's a bit annoying to not know when your car is showing brake lights; I put a little reflector in the back of mine because I wanted to see when the cruise control actually activated the brake lights - It turns out it brakes quite strongly (Like, 2nd-gear strongly!) with just engine-braking before it uses the brake lights, which is now another reason why I disable cruise control when cars are slowing down ahead and handle it myself!!

 

[Empty Sea]

Thanks for the helpful responses - which also answer a similar query about slowing down when using the Dynamic Radar Cruise Control. For anyone following, it may indeed appear that the driver of the car is braking a lot, when, in fact, it's just the accelerator being eased off.

[Cyker]

TBH it's a non-issue either way - Manual drivers who use engine braking can slow down just as quickly without brake lights, and many people in normal cars are often pressing on the brake pedal randomly and for no apparent reason (I was behind a Nissan Primera the other day and it was like they were transmitting morse code or something, the amount of random braking they were doing. Not just to slow for bends or traffic but even just in the middle of a clear straight road! The stupid thing was I was still somehow slowing down faster than they were and I wasn't braking most of the time! I can only imagine they had a faulty brake switch or very big feet!)

 

[wivenhoe]

My Lexus RZ has the option to show in the central screen when the brake lights are on. This shows them being on when regenerative braking is happening. 

[Cyker]

Ooh that's neat, never seen a car you could do that with!

[jthspace]

I recently had to drive a school minibus, even though I have a licence the council insisted I take a day-length driving course and test. Driving along all OK, approaching a round-about changed down gears to be in the right gear to either stop or accelerate. Did it again at traffic lights and next roundabout. Told I would fail the test as I have to pull up in the gear I’m in (could be 6th) and then select 1st to pull away.  My nephew is a driving instructor and said this is how they teach driving these days. I also drive my friends 16 gear tractor but that one I can leave in 8th all day long 😂. 

[Cyker]

I don't think they'd fail you for that, but I was also taught to stay in gear when slowing to a stop. I think the idea is to lesson the workload, and give you more brain space to check mirrors and blindspots and such, and forgetting those because you're downshifting would attract minors

However, for things like roundabouts, I was taught to be in an appropriate gear when on approach in case I had an opportunity to go, as you will pick up minors for missing opportunities to go.

It kinda makes sense to me because if I'm going to stop anyway (e.g at lights that have just turned red), why go to the effort of shifting down through the gears, but where you are just slowing and maybe not stopping (e.g. at roundabouts or lights that have been red for a while), it makes absolute sense to shift to a more appropriate gear - Again you can pick up minors if you are not in the right gear and have to scrabble for the right gear at the last moment, esp. since you're usually in a situation where you should be checking mirrors and blind spots when that happens.

Alas all that time I honed those skills are wasted since I now have a hybrid!

 

[Rhymes with Paris]

Aye, that method does not make sense to me either.

It certainly wouldn't work with a sequential gearbox such as on motorcycles, where you have to anticipate and change down aiming to be in second when you have to stop.

Then only one click to neutral, and another for first to pull away again.

I was once told by a IAM instructor that gears are for going, and brakes for stopping on a car.

When queried, the reason given was that in the unlikely event of brake failure, you wouldn't know about it until too late if using gears to slow down.

Quite what you are meant to do if discovering brake failure in a higher gear was not elaborated upon.

So I still think that even in that highly unlikely scenario, it is better to be  changing down, and in usual situations too, with braking if needed.

Only had total failure once in a borrowed Morris 1000 van, no option but to change down through the gears until in second, then handbrake to stop.

So that IMO alone makes nonsense of keeping in a higher gear until stopped.

 

[philip42h]

17 hours ago, Empty Sea said:

Thanks for the helpful responses - which also answer a similar query about slowing down when using the Dynamic Radar Cruise Control. For anyone following, it may indeed appear that the driver of the car is braking a lot, when, in fact, it's just the accelerator being eased off.

Well, yes and maybe no ... the RAV has relatively light regenerative braking so probably doesn't show the brake lights under a normal 'lift off' - whether under driver control or adaptive cruise control. But, if under adaptive cruise control the car decides that it needs to stop it certainly does hit the brakes, potentially very hard! 😉

[philip42h]

1 hour ago, Rhymes with Paris said:

gears are for going, and brakes for stopping

I've been told that too - and generally believe that to be the case. If you want to bring the car to a stop, use the brakes - that's what they are there for. But that doesn't mean that you shouldn't put the car into the correct gear to get the benefit of a little engine braking when going down a long hill ...

It's getting all a bit academic in these days of 'gearless' EVs and eCVT hybrid 'automatics' but going back a few years to when I last drove a manual I would always want to be in a gear that was appropriate for the speed and rate of acceleration / deceleration that I was doing - I wouldn't want to depress the clutch to disengage the gearbox until I was effectively at a standstill. And the appropriate gear would be as much determined by what I expected to do next as to what the car is doing right now.

[adidev]

2 hours ago, philip42h said:

4 hours ago, Rhymes with Paris said:

gears are for going, and brakes for stopping

I've been told that too - and generally believe that to be the case. If you want to bring the car to a stop, use the brakes - that's what they are there for. But that doesn't mean that you shouldn't put the car into the correct gear to get the benefit of a little engine braking when going down a long hill ...

I'll throw my 5p here - this was old school. With modern ICE, if you're using motor to slow down, the fuel is shut off while the motor is spinning, providing load to the gearbox. Whne you clutch, the motor needs fuel to spin - less efficient

[Rhymes with Paris]

Well , I am old school.

And so is the Yaris I run.

I don't have any experience driving newer cars made after 2012,so maybe a different technique needed now with the newer ones.

 

[Cyker]

7 hours ago, philip42h said:

Well, yes and maybe no ... the RAV has relatively light regenerative braking so probably doesn't show the brake lights under a normal 'lift off' - whether under driver control or adaptive cruise control. But, if under adaptive cruise control the car decides that it needs to stop it certainly does hit the brakes, potentially very hard! 😉

No hybrid will trigger the brakelights on lift off - They generally simulate light engine-braking, 4th/3rd-gear ish levels, so it's not really needed.

It's specifically the 1-pedal driving modes where they tend to do it. e.g. the Kona has 4 levels of regen braking, and levels 1 and 2 won't trigger the brakelights, but 3 and 4 will because they slow the car much harder. Likewise the Leaf won't unless you turn on the one-pedal driving mode, then it will when slowing the car down above a certain rate.

But yes, the adaptive cruise will light up the brakes when stopping or in its rabid desire to hold a gap, usually braking uncomfortably hard!!   It really could do with a lot more finesse - it tends to brake far too much and use the B-mode engine braking, which is already quite strong but doesn't trigger the brake lights, which has scared people behind me a bit on the motorway in medium speed traffic. The problem is it sees the car in front slow and tries to keep the same gap instead of letting it close for a gentler braking. When the car in front stops abruptly, it'll really slam on the anchors even tho' it's a couple truck lengths in front which has knocked the wind out of me a few times!

It often does it in situations where I wouldn't even bother to brake and would just lift off and let the light regen/MG2 simulated engine braking slow me down - Because it leaves such a big gap in front that's usually more than enough, especially if the cars ahead usually move off again long before I get anywhere near them!

But this is all why as soon as I see people slowing ahead I immediately hit the massive CANCEL button and take over, as I can just do a much better job of slowing the car down without bruising everyone's ribs  

I'm just glad it's a button - If that was a touch control I think I would have been in many accidents by this point...!  

[ernieb]

This was a very long time ago but I failed my first driving test because I did not use the 'engine brake' enough. That was back in the days when an emergency brake was a rope and anchor tied to the rear bumper. 😇

[Abhinash]

hi guys

abhinash here owner of a 2023 bz4x in Vancouver

with regards to Empty Sea ( Martin ) question, yes the brake lights do come ON when you lift your foot off the accelerator pedal in regenration mode i.e the switch is on.

i've personally tried this many times even at low speeds and they do come on.

[wivenhoe]

You can see the red lines on the bottom of the screen below the music track info - they appear when the brake lights are on in my RZ. They are not shown by default, you need to select them in the screen set up menu. Are you sure the bz isn’t configurable like The RZ ?