Regeneration brake light

[Jomarkh]

I put this on the back of the car this morning

 

[jamesie]

Just put....."If you can read this you are too close.....back off!"

 

[Kithmo]

I put this on the back of the car this morning

Bear in mind most ICE drivers won't know what KERS is.
My "Warning Protected by Nextbase Dash Cam" sticker usually has them backing off if they get close enough to read it.

 

[Les burrows]

DO BRAKE LIGHTS WORK IN REGEN? NO THEY DO NOT
Hi everyone just flicking trough so old threads on the forum yesterday and came across this one again about do the brake lights come on when the car is in regen
Well I can only speak for what I have found out today in my own MG5

This is what I did this morning I removed the cover for the high level brake light from inside the tailgate got at the wiring for the said light and connected an extra cable to it I then ran the cable through the car and connected a small beeper to the other end so now every time the brake light operates the beeper goes off and than went for drive to do some tests and this is what I found

1 the brake lights only work in TWO ways only, they come on when you press the footbrake (obviously) and the only other time they are on is when the GREEN (P) is ALIGHT in the dash, that’s when the auto hold button is alight the one marked (A) then the brake lights stay on until you move off again or select P when the parking brake is on in the dash there is a (P) in RED this is like the handbrake and the brake lights or not on in this mode

So to comfirm
I drove the car for several miles with this bleeper set up and tried every mode possible from 10-60 MPH and no matter if it was in Eco / Normal/or Sport and no matter which KERS setting I used in any of the modes the brake lights do not come on unless you use the foot brake in KERs 3 from almost 70 I took my foot off the pedal to get as much regen as possible still nothing from the bleeper
So Brake Lights Do Not work in Regen 1/2/or3
Pictures below
1 inside off tailgate high level brake light cover
2 cover removed
3 wiring and plug for high level brake light
4 extra cable now attached
5 sound beeper on sunvisor
Could have use a light bulb but the sounder was for better in daylight
Hope this answers some of the questions in the thread
As I said mine is the MG5
Les

 

[n8sail]

Thanks for the great testing, Les!

Indeed concerning. Driving where I live is dangerous enough as it is (Thailand is consistently top 3 in the world for deaths on motorways!) Already had a few people act aggressively towards me after a 'quick' slow down in KERS 3. I have started just touching the brake pedal in situations where it looks like following drivers are too close now, but then of course you cannot modulate your KERS stopping power then other than flicking the level down.

Any dashboard lights/alarms appear with the extra wiring and beeper wired in circuit? I believe some modern cars with CAN bus will throw errors or codes when a bulb is out. Usually this is detected by change in resistance of the circuit... adding a few meters of cable and a different load to the circuit might trip it off, or perhaps the MG5 just doesn't use this feature in CAN bus protocol.

 

[Les burrows]

Thanks for the great testing, Les!

Indeed concerning. Driving where I live is dangerous enough as it is (Thailand is consistently top 3 in the world for deaths on motorways!) Already had a few people act aggressively towards me after a 'quick' slow down in KERS 3. I have started just touching the brake pedal in situations where it looks like following drivers are too close now, but then of course you cannot modulate your KERS stopping power then other than flicking the level down.

Any dashboard lights/alarms appear with the extra wiring and beeper wired in circuit? I believe some modern cars with CAN bus will throw errors or codes when a bulb is out. Usually this is detected by change in resistance of the circuit... adding a few meters of cable and a different load to the circuit might trip it off, or perhaps the MG5 just doesn't use this feature in CAN bus protocol.

Hi n8sail this test I did was just a temporary wiring job to to prove if the brakes worked or not under regen and no they do not the wiring and the beeper have now been removed I’m sorry if I may have confused you in anyway and yes I know some vehicles will give you an alert if you have a bulb out my skoda Superb did that and it was very useful to have
Just be carful when slowing with high regen as traffic behind you I no idea and you can slow down quite quickly in kers 3
Les

 

[Cocijo]

Hi n8sail this test I did was just a temporary wiring job to to prove if the brakes worked or not under regen and no they do not the wiring and the beeper have now been removed I’m sorry if I may have confused you in anyway and yes I know some vehicles will give you an alert if you have a bulb out my skoda Superb did that and it was very useful to have
Just be carful when slowing with high regen as traffic behind you I no idea and you can slow down quite quickly in kers 3
Les

Good test Les. On the ZS I’m told that the brake lights work in regen3 and are based on a decelerometer - greater than a certain level of deceleration and they come on - I’ve not tested this though. It is definitely something to be aware of when driving these cars as many road users seem to completely rely on brake lights on the car in front to tell them when to slow down.

 

[Les burrows]

Good test Les. On the ZS I’m told that the brake lights work in regen3 and are based on a decelerometer - greater than a certain level of deceleration and they come on - I’ve not tested this though. It is definitely something to be aware of when driving these cars as many road users seem to completely rely on brake lights on the car in front to tell them when to slow down.

Hi Cocijo thanks for your reply not sure if you have a 5 or ZS but some on this thread appeared to be under the same impression that the lights came on at certain levels of deceleration on the 5 which is why I did this testing to find out the true story it needs someone to do the same thing with the ZS it’s not difficult and takes very little time I think using a buzzer/bleeper is the best way as you can’t miss it while looking away ie watching traffic for example as you might do with a little bulb in daylight and sunshine, the one I used is only small but at 100dbs you certainly hear it and of course it only sounds when the brake light is on
Les

 

[Dt99idr]

Hi Les, how about repeating the test with a decelerometer in the car? If you have a phone with one built in... In my car I didn't think I got above the 0.3 legal limit.

Ian

 

[Les burrows]

Hi Les, how about repeating the test with a decelerometer in the car? If you have a phone with one built in... In my car I didn't think I got above the 0.3 legal limit.

Ian

Hi lan don’t see what that would do or prove all I know is the MG5 brake lights do not come on at any speed or in any setting and how you can slow down faster than KERS 3 in any mode I don’t know unless of course you run into something in front of you or apply the brakes then the lights will come on
Les

 

[rogerco]

no matter which KERS setting I used in any of the modes the brake lights do not come on unless you use the foot brake in KERs 3 from almost 70 I took my foot off the pedal to get as much regen as possible still nothing from the bleeper

Interesting test. I think perhaps that if you don't use the footbrake pedal then even in Kers3 at 70 the deceleration will not be sufficient to trigger a light.

If you are in Kers3 and you do put your foot on the brake lightly then you can see that the power meter goes deeper into the blue as the deceleration is handled by the Kers. In this case I would expect the brake light to come on.
(it may be that it is nothing more than a conventional switch on the pedal).

If in kers3 you press the pedal a bit harder you can see that the brakes are starting to work as the power meter doesn't move so far into the blue. This should certainly put the brake lights on.

This is just a working hypothesis -
a) with no pedal pressed at any speed on the flat the deceleration is not sufficient to require a light. This is demonstrated by @Les burrows test.

b) with no pedal pressed going up a hill it (say greater than 8%) it might be that kers and gravity (conversion of kinetic to potential energy) combined could be enough to trigger a brake light.
? not tested by Les? Need to find an empty motorway with a long steep climb and re-test.

c) with the brake pedal pressed just enough to make all of the deceleration come from Kers the brake light should come on (switch on pedal?).

Since the brake light comes on if you are stationary and touch the brake pedal (try it reversing up to something so you can see the reflection) my guess is that there is a conventional switch on the pedal - which will be triggered by kers braking if you are touching the pedal - and the only 'clever' bit is the hill start (auto hold) mode where Les's test shows that the brake light comes on when you move from P to D and take your foot off the pedal so that the car stays stationary against the hill instead of gliding off.

 

[Petriix]

Hi lan don’t see what that would do or prove all I know is the MG5 brake lights do not come on at any speed or in any setting and how you can slow down faster than KERS 3 in any mode I don’t know unless of course you run into something in front of you
Les

Well done for doing the test, Les. It's useful information.

The point about deceleration is to assess whether or not there are any circumstances where the brake lights fail to display when deceleration exceeds the legal limit at which they should turn on. There is speculation that, even in KERS 3, the deceleration does not ever pass that threshold and therefore it's not as serious an issue. It would be useful to test that theory just in case it turns out to be illegal.

I take on board the notion that you think the brake lights not showing under the deceleration of KERS 3 is dangerous, while not necessarily a legal requirement. My suggestion is that you get into the habit of applying light pressure to the brake pedal whenever you think the brake lights should be on. Not ideal, but safer then not.

 

[rogerco]

how you can slow down faster than KERS 3 in any mode

by putting your foot on the brake pedal in kers3 it continues to increase the regen until it limits and then applies the brake. That will be a faster deceleration than simply taking your foot off the pedal.
Try it going down a very steep hill at relatively slow speed to see the effect. No pedal will (if the slope is right) hold a constant speed with some regen, foot on the brake will initially increase the regen to slow the car down.

 

[Adee]

Hi Les, how about repeating the test with a decelerometer in the car? If you have a phone with one built in... In my car I didn't think I got above the 0.3 legal limit.

Ian

Hi. I already did this and reported it earlier in the thread. I'm of the opinion that the brake lights under a certain deceleration should come on. They've done it on the SUV, why not do it on the MG5 - I can't see the logic? This is a safety issue that they should address ASAP before too many road rage incidents accumulate. I didn't get much support in my views, however.

 

[Alb]

It's probably something that can be changed in software but whether it will is another story entirely.

 

[Severnless]

Just thought I would add to this thread, with the KERS on the MG5 is nothing compared to the ZS, which imho is not far off an e-pedal ala leaf
I only need to touch the breaks in our ZS when coming to a stop (kers3)
Where our 5 you almost need to use the brakes all the time (kers3), i also notice as others have that the power needle moves hard over into regen when you first touch the brakes.
I suppose the thought behind low regen (kers3) and no brake light is it’s more like driving a conventional ice car?

 

[rogerco]

Perhaps the difference (ZS vs 5) is simply that in the ZS up to full regen is applied by easing of the "accelerator" pedal and hydraulic braking is applied as soon as you touch the brake pedal. (I haven't driven a ZS so might be wrong about this)

In the 5 only mild regen is applied by taking the foot off the accelerator pedal, and then when you apply the brake pedal more regen is applied until your demand for stopping (pressure on the pedal) exceeds the deceleration that regen alone can provide at which point the hydraulic brakes are activated.

So in the 5 it is not really a brake pedal, it is a "decelerate" or "stop" pedal which can bring you to a (near) stop without ever applying the brakes.

This would also explain some of the confusing (to me) debates about the (dis)benefits of using kers in motorway driving. In the ZS it might be true that kers on a motorway is inefficient as you'll never get back what you save, but in the 5 there is little kers effect from the accelerator pedal, kers tends to only get used when in an ICE you would apply the brake pedal (in the 5, using the decelerate pedal).

In the 5 you are getting something more like an engine braking effect in an ICE, Kers1-3 changes the amount of engine braking effect simply from the accelerator pedal. Engine braking in an ICE does not put your brake lights on even if you bang it into 2nd gear at 70mph.

I like the way it works in the 5, and yes, I suppose it is more like an ICE in that respect - one pedal makes you faster and one pill makes you slow (and the ones that mother gives you don't do anything at all, to complete the Grace Slick reference)

 

[rogerco]

They've done it on the SUV, why not do it on the MG5

as said above - because in the 5 most of the kers effect comes from using the decelerate pedal, the amount that comes from taking foot off the accelerator is simply like engine braking in an ICE and not enough to merit a brake light.

 

[Adee]

In my "5", KERS3 provides some pretty potent stopping power without going anywhere near the brakes. I can complete the majority of most journeys without using the brake pedal at all if I anticipate road conditions properly. I'm pretty sure that the brakes are just brakes - you press the pedal and the pads squeeze the discs - no "extra KERS". The only comment I would make is that KERS "braking" from accelerator lift-off gets better as the battery depletes - in fact KERS3 won't engage at all if the battery is >95%full. This is obviously because there is no "room" in the battery to receive any extra charge from the KERS - i.e. to stop the battery from being overcharged, I suppose. Personally I love the KERS and use it all the time to get some fairly useful range estimates from the GOM. It's currently showing a combined GOM + actual mileage estimate of about 245miles after 165miles travelled (i.e. the GOM shows 80miles remaining).
Maybe there are some s/w differences - my car is under 2months old.

 

[Les burrows]

Interesting test. I think perhaps that if you don't use the footbrake pedal then even in Kers3 at 70 the deceleration will not be sufficient to trigger a light.

If you are in Kers3 and you do put your foot on the brake lightly then you can see that the power meter goes deeper into the blue as the deceleration is handled by the Kers. In this case I would expect the brake light to come on.
(it may be that it is nothing more than a conventional switch on the pedal).

If in kers3 you press the pedal a bit harder you can see that the brakes are starting to work as the power meter doesn't move so far into the blue. This should certainly put the brake lights on.

This is just a working hypothesis -
a) with no pedal pressed at any speed on the flat the deceleration is not sufficient to require a light. This is demonstrated by @Les burrows test.

b) with no pedal pressed going up a hill it (say greater than 8%) it might be that kers and gravity (conversion of kinetic to potential energy) combined could be enough to trigger a brake light.
? not tested by Les? Need to find an empty motorway with a long steep climb and re-test.

c) with the brake pedal pressed just enough to make all of the deceleration come from Kers the brake light should come on (switch on pedal?).

Since the brake light comes on if you are stationary and touch the brake pedal (try it reversing up to something so you can see the reflection) my guess is that there is a conventional switch on the pedal - which will be triggered by kers braking if you are touching the pedal - and the only 'clever' bit is the hill start (auto hold) mode where Les's test shows that the brake light comes on when you move from P to D and take your foot off the pedal so that the car stays stationary against the hill instead of gliding off.

Hi Roger all I can tell you is I did what I could to try and find if the brake lights work under regen conditions only.
Of course the lights will come on if you press the brake pedal even a small amount about 15mm we all know that and that’s the same i think for all vehicles or should be, but if i did not touch the brake pedal and just let the car slow under regen from any speed in and mode or kers setting the lights do not come on.
I just drove in a normal way on public roads to find out whatever I could with a length of bell flex and a small beeper and i have listed my finding #44 of this thread.
Now if you or someone else wants go into the Sciences or try something I didn’t with deceleration meters and hills of 8% on a motor climb or decent then please do and then let us have the results after it’s done, as for me I will be using kers as much as I can to get as much energy back into the battery and to save on brake wear but I will not be relying on it to let anyone behind me know that I’m slowing down I will just use the brakes gently along with the kers as I would in an ICE car after all it does basically what engine braking does in an ice and as far as I know that does not operate ice car brake lights ether, but when I’m sure it is safe to use KERs as much as possible of course I will do if other vehicles are well behind or nothing is behind me on the road.
The point of the post was to say don’t think KERS puts your brake lights on in everyday driving it doesn’t
Les