Regeneration brake light

[Les burrows]

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.

Hi pentrix just wanted to point I never said anywhere about the brake lights under regen being dangerous or illegal and your suggestion that I apply light pressure to the brake pedal that is something I have always done I was just trying to establish what did happen when you take your foot off the accelerator but I thank for you comments on the useful information I hope others have found the same and no longer think regen means brake lights are on No No.
Les

 

[Les burrows]

Hi here’s a thought is it possible that the difference between the two cars the 5 And the ZS is the MG pilot I think it’s called and the adaptive cruise control on the ZS Which is not on the MG5 ?
The adaptive CC will slow the car automatically if need be I think and also does the ZS not default to KERS 3 on start up where the 5 default is KERs 2 so in the ZS if it starts to brake or slow down via regen then maybe the lights for braking would come on automatically!.
I have never driven a ZS but maybe this is where the confusion as come from.

I’m certain the lights do not come on on the five unless you use the footbrake or the auto hold control when stopped in traffic #44
Les

 

[Petriix]

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.

That's objectively not true. The brake pedal uses regenerative braking as much as possible before engaging the friction brakes mechanically in the latter part of the pedal travel. This is easily measurable by watching the power flow screen while slowing in KERS 1: when you apply the pedal, the amps flowing back into the battery significantly increase and the power meter goes further into the blue 'charge' section. It works just like any hybrid in that regard.

 

[Petriix]

Hi pentrix just wanted to point I never said anywhere about the brake lights under regen being dangerous or illegal and your suggestion that I apply light pressure to the brake pedal that is something I have always done I was just trying to establish what did happen when you take your foot off the accelerator but I thank for you comments on the useful information I hope others have found the same and no longer think regen means brake lights are on No No.
Les

Don't worry, I'm just extrapolating. I'm not personally worried, but it wouldn't surprise me if MG have made a mistake with this in terms of the legality. It would be great to know for sure.

 

[Adee]

That's objectively not true. The brake pedal uses regenerative braking as much as possible before engaging the friction brakes mechanically in the latter part of the pedal travel. This is easily measurable by watching the power flow screen while slowing in KERS 1: when you apply the pedal, the amps flowing back into the battery significantly increase and the power meter goes further into the blue 'charge' section. It works just like any hybrid in that regard.

The power meter should be an accurate representation of what's going on, as you say. And if it goes further into the blue when you brake then it does suggest there is more regenerative braking being applied via the brake pedal. Does it go further into the blue, the harder you brake? Maybe this only happens in KERS1? I will check it out but until then I remain skeptical as it would be madness and overly complicated to have two pedals feeding into the regenerative braking system in my view. If the regen braking increased by increased pressure on the brake, there would be no benefit to having three KERS settings

Whatever the outcome I still maintain that KERS3 which does not activate the brake lights is un-necessary and bordering on dangerous.

 

[Petriix]

The power meter should be an accurate representation of what's going on, as you say. And if it goes further into the blue when you brake then it does suggest there is more regenerative braking being applied via the brake pedal. Does it go further into the blue, the harder you brake? Maybe this only happens in KERS1? I will check it out but until then I remain skeptical as it would be madness and overly complicated to have two pedals feeding into the regenerative braking system in my view. If the regen braking increased by increased pressure on the brake, there would be no benefit to having three KERS settings

Whatever the outcome I still maintain that KERS3 which does not activate the brake lights is un-necessary and bordering on dangerous.

Thankfully hybrid and EV designers don't share your view on this, otherwise we'd all be wasting a lot more energy for no good reason. In my view, it would be madness for the brake pedal to only use friction.

 

[Adee]

Thankfully hybrid and EV designers don't share your view on this, otherwise we'd all be wasting a lot more energy for no good reason. In my view, it would be madness for the brake pedal to only use friction.

I agree that you'd want to implement as much regenerative braking as possible otherwise energy would being wasted, but my point is that I don't think (in KERS3 mode at least) that there is any more regenerative braking to be had once you foot is off the accelerator. I'll check it though and report my findings.

 

[Severnless]

I agree that you'd want to implement as much regenerative braking as possible otherwise energy would being wasted, but my point is that I don't think (in KERS3 mode at least) that there is any more regenerative braking to be had once you foot is off the accelerator. I'll check it though and report my findings.

May I respectfully suggest you just enjoy what you’ve got?!
Life is to short, if there’s a problem, you don’t like how the brake lights don’t come on, when you take your foot off the go pedal, then take it back to mg and ask for them to give you your money back.

 

[Petriix]

I agree that you'd want to implement as much regenerative braking as possible otherwise energy would being wasted, but my point is that I don't think (in KERS3 mode at least) that there is any more regenerative braking to be had once you foot is off the accelerator. I'll check it though and report my findings.

You're still incorrect in your supposition. The simple test is to measure your approach to the same junction twice: once just using KERS and once using the brake pedal as well. Ideally pick a roundabout on a dual carriageway and slow from 70mph. Look at the power information screen and note the negative ampere value. I've done this. There is a significant difference.

 

[Adee]

OK guys. Well that's me told.

 

[Adee]

You're still incorrect in your supposition. The simple test is to measure your approach to the same junction twice: once just using KERS and once using the brake pedal as well. Ideally pick a roundabout on a dual carriageway and slow from 70mph. Look at the power information screen and note the negative ampere value. I've done this. There is a significant difference

Petriix - you are right that further regenerative braking is applied with the brake pedal in all KERS modes. However it does not appear to occur until significant braking has commenced which seems odd to me. Why allow some regenerative braking with the accelerator pedal, then some braking with the hydraulic brakes and then bring in more regenerative braking later. This means that energy is being unnecessarily wasted to the brakes when it could be recovered to the battery. The most energy efficient way of implementing it would be to enable as much regenerative braking as possible/necessary using the accelerator pedal and then use the hydraulic brake as additional braking when required. Hence my original stance. I suspect it is down to driveability and how people might struggle to adjust to heavy regenerative braking from a single pedal. It does suggest that driving in KERS3 mode may not be as beneficial as I first thought relative to KERS1 if you get extra regenerative braking in the other KERS modes under braking.

 

[rogerco]

but my point is that I don't think (in KERS3 mode at least) that there is any more regenerative braking to be had once you foot is off the accelerator.

I think the opposite - perhaps not on the flat, but certainly if you are coming downhill the power meter in Kers3 goes further into the blue as you apply the brake pedal (as I said above)(in the MG5)

 

[Les burrows]

Hi In this thread #62 I asked could the ZS be different and asked about the adaptive cruise control I have not seen any reply to that posting so I read the MG web site just today I found the information below and it does appear the the the ZS does brake its self when using the ACC so it must put the brakes on to slow down therefore if the brakes are being applied by the ACC then the brake lights might well come on on the ZS but but not on the MG5 as it is not fitted with ACC that’s how I read it anyhow I hope this now puts this matter to bed.​

Les

​

WHAT IS ADAPTIVE CRUISE CONTROL?​

Adaptive cruise control, sometimes referred to as ACC, is an intelligent form of cruise control that uses radar and cameras to automatically accelerate and brake to maintain a safe distance from the car in front. When the path ahead is clear, the car will continue at a pre-set speed. It has the capability to speed up if a slower car pulls over and can slow down if a car travelling at a slower speed pulls in front of you. Some adaptive cruise control systems can also take control in stop-start traffic jams and even read speed limit road signs.

 

[rogerco]

Why allow some regenerative braking with the accelerator pedal, then some braking with the hydraulic brakes and then bring in more regenerative braking later.

That would indeed be odd/daft, but I've not seen that it does that.

I agree it is down to driveablility, and from a comment above I gather that in the ZS all the regen comes from reducing pressure on the accelerator pedal and the brake pedal is purely hydraulic - I don't know if this is true or not, but it was implied.

In the 5, i observe in all kers modes that there is some regen slowing from easing pressure on the accelerator pedal (analogous to engine braking in an ICE), but then there is more regen when you start to apply the brake pedal before the hydraulics are called on.

I could be wrong about this, but that squares with what I observe watching the power meter as I slow down.

For me the MG5 system, whatever it actually is, seems to be very like an ICE - you get some, but not excessive, 'engine' slowing without using the brakes - in kers3 slightly more than was the case in my previous ICE (a honda civic vtec), and about the same is in an overloaded VW t4 diesel van, then you apply the brake and you get more regen until it limits and then hydraulic.
In kers1 the engine braking effect is more like the honda civic, so of course there is more regen to be had once you apply the brake pedal than in kers3.

The brake light comes on when you touch the brake pedal, whether or not the pedal is demanding regen or hydraulic slowing.

 

[Severnless]

Hi In this thread #62 I asked could the ZS be different and asked about the adaptive cruise control I have not seen any reply to that posting so I read the MG web site just today I found the information below and it does appear the the the ZS does brake its self when using the ACC so it must put the brakes on to slow down therefore if the brakes are being applied by the ACC then the brake lights might well come on on the ZS but but not on the MG5 as it is not fitted with ACC that’s how I read it anyhow I hope this now puts this matter to bed.​

Les

​

WHAT IS ADAPTIVE CRUISE CONTROL?​

Adaptive cruise control, sometimes referred to as ACC, is an intelligent form of cruise control that uses radar and cameras to automatically accelerate and brake to maintain a safe distance from the car in front. When the path ahead is clear, the car will continue at a pre-set speed. It has the capability to speed up if a slower car pulls over and can slow down if a car travelling at a slower speed pulls in front of you. Some adaptive cruise control systems can also take control in stop-start traffic jams and even read speed limit road signs.

Mmm, I can say that when using acc (/ mg pilot) the ZS does not use the KERS to slow down, it uses the brakes, as it is a retro fit from the ice ZS
Which we can all agree is bonkers.

 

[Petriix]

Petriix - you are right that further regenerative braking is applied with the brake pedal in all KERS modes. However it does not appear to occur until significant braking has commenced which seems odd to me. Why allow some regenerative braking with the accelerator pedal, then some braking with the hydraulic brakes and then bring in more regenerative braking later. This means that energy is being unnecessarily wasted to the brakes when it could be recovered to the battery. The most energy efficient way of implementing it would be to enable as much regenerative braking as possible/necessary using the accelerator pedal and then use the hydraulic brake as additional braking when required. Hence my original stance. I suspect it is down to driveability and how people might struggle to adjust to heavy regenerative braking from a single pedal. It does suggest that driving in KERS3 mode may not be as beneficial as I first thought relative to KERS1 if you get extra regenerative braking in the other KERS modes under braking.

You're still fundamentally misunderstanding how the brake pedal works. The hydraulic braking doesn't apply at all until maximum regenerative braking is applied; even though you're using the brake pedal, don't assume that the pads are pressed against the disks.

The braking force is electronically assisted to ensure that the overall combination of regen and friction is consistent and progressive with the pedal travel even when different amounts of regen are possible (if, for example, the battery is full).

 

[Les burrows]

I have switched my mg zs ev for the mg5 ev, happy with the mg5 but unlike the mgzs ev I don't think the brake lights come on with heavy regeneration had anyone else noticed this,is it normal or is there a fault.

Right everyone we appear to be slipping away from the thread with this Jeff started it off and asked has anyone notice the brake lights don’t come on under heavy regenerative braking on the MG5
Well Jeff I did a little test on this read #44 and I will stick my neck out and say your dead right the MG5 brake lights do not come on with Regen braking at any level or in any mode you need to touch the brake pedal as well if you have some one close behind and need to warn them your slowing down I don’t believe this is a fault or it’s in any way dangerous has as far as I know this is ICE car technology
Les

 

[Adee]

You're still fundamentally misunderstanding how the brake pedal works. The hydraulic braking doesn't apply at all until maximum regenerative braking is applied

From my experience, I think you're incorrect there. There is significant braking from the hydraulic system before the power needle swings further into the blue. Try it.

 

[Adee]

You're still fundamentally misunderstanding how the brake pedal works. The hydraulic braking doesn't apply at all until maximum regenerative braking is applied; even though you're using the brake pedal, don't assume that the pads are pressed against the disks.

The braking force is electronically assisted to ensure that the overall combination of regen and friction is consistent and progressive with the pedal travel even when different amounts of regen are possible (if, for example, the battery is full).

This was quite an interesting article I found.....

Best And Worst Electric Cars For Regenerative Braking

Based on a few days behind the wheel of the Model 3, we believe that Tesla sets the gold standard for EV braking feel.

insideevs.com

It seems as though different manufacturers implement regenerative braking in different ways. It suggests that they are trying to optimise the systems for driveability rather than for pure efficiency? But it's not a very technical article - rather subjective.

 

[ArfurM]

Not that it counts for much, but I asked the MG dealer about this very point and he said that in KERS3, the brake lights will come on (which they should IMHO, given the amount of retardation you get), but it seems this may not be the case. I will certainly be checking this when I pick mine up...