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Citroën ë-C4 Shine Plus 2021
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Discussion Starter · #1 ·
Been informed by a friend who drove behind me the other night that apparently I had dropped 10 mph and not had the brake lights come on when coasting up to a roundabout, and that they hadn’t realised I was slowing down other than the fact that the gap had significantly shrunk between us.

I’ve now verified this by just lifting off before red lights and the car will drop all the way down to 5 mph from 50 mph with no brake lights coming on, which is a major safety concern when pulling in/out on motorways and in town as well. I drive 99% of the time in B mode anyway since it makes life so much easier, as well as improving efficiency, but the fact that I can and do slow all the way down from 70 mph to 20 mph on dual carriageways with roundabouts with no brake lights coming on scare me.

Anyone else able to verify this with their car?

Thanks, Citroën needs to sort this out if it’s a widespread issue and fast.
 

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Nissan LEAF30
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This is the same as engine braking in an ICE, that doesn't show brake lights either. B mode is the equivalent of changing out of top in an ICE into 4th to slow the car without using the brakes. If this scares you in terms of the idiots behind you only driving on your lights then use your brakes rather than B mode - you still get the same Regen but the brake lights will be on.
There's legislation that sets out when brake lights must work, between 0.17g and 0.3g it's optional on new cars, below it mustn't, above it must. If your car is pulling more than 0.3g on Regen alone I'd be surprised, but if so take it back to Citroen. They can test it with a Tapley meter but I suspect that you'll either get blank looks or laughed at and told that they all do that.
 

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GOLF GTE PHEV
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You can slow an ICE with a manual gearbox especially, very strongly by dropping down the gears. If you are being followed you'd normally just apply the brakes gently to illuminate the brake light as a warning.
 

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You can slow an ICE with a manual gearbox especially, very strongly by dropping down the gears. If you are being followed you'd normally just apply the brakes gently to illuminate the brake light as a warning.
Sure, but you’d also touch the brake pedal lightly no?
Does B mode in that car actually feel like braking? If you can drive the car in B mode without really having to use the brakes (and not just like engine braking) then I’d say you’re getting the level of retardation that should trigger the brake lights.

what does the manual say?
 

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Having the brake lights still wired to the friction brakes as in an ICE vehicle makes sense.
Depending on the design, an EV or hybrid might blend in use of the friction brakes when slowing to a stop with one-pedal driving modes.
Unnecessary brake lights at any rate of deceleration will cause over-reactions by following drivers, which on an otherwise free-flowing road will cause bunching or standstills in following traffic.
Therefore, many EVs will only illuminate the brake likes when the actual brakes are engaged (by pressing the brake pedal or the one-pedal driving systems blending in use of friction brakes) seems a fair solution, and reflects what other following drivers would expect vis-a-vis engine braking.

If you were approaching a roundabout, the following driver should also have anticipated that approaching a roundabout there would be vehicles slowing down. The car in front might be an ICE using engine braking to slow down, and they should expect that.
 

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As @dk6780 points out there are rules for the makers to obey regarding brake lights including when using regenerative braking.
As the settings are laid down in UN and EU regulations I have to assume the eC4 obeys the rules, They would be in trouble with the authorities otherwise, the car would be non-compliant and unable to be sold.
 
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Having the brake lights still wired to the friction brakes as in an ICE vehicle makes sense.
Depending on the design, an EV or hybrid might blend in use of the friction brakes when slowing to a stop with one-pedal driving modes.
Unnecessary brake lights at any rate of deceleration will cause over-reactions by following drivers, which on an otherwise free-flowing road will cause bunching or standstills in following traffic.
Therefore, many EVs will only illuminate the brake likes when the actual brakes are engaged (by pressing the brake pedal or the one-pedal driving systems blending in use of friction brakes) seems a fair solution, and reflects what other following drivers would expect vis-a-vis engine braking.

If you were approaching a roundabout, the following driver should also have anticipated that approaching a roundabout there would be vehicles slowing down. The car in front might be an ICE using engine braking to slow down, and they should expect that.
See Spiny's reply. It's prescribed in terms of deceleration level
It's not up to individual auto makers whim if they want to sell compliant legal cars.
 

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Discussion Starter · #9 · (Edited)
Went to the dealer today for another issue, but asked about it and got given the following information from the technical manual. Dealer agrees it is non-compliant, but can't do anything about it until Citroën issues a recall or TSB.

There's legislation that sets out when brake lights must work, between 0.17g and 0.3g it's optional on new cars, below it mustn't, above it must. If your car is pulling more than 0.3g on Regen alone I'd be surprised, but if so take it back to Citroen.
The manual clearly states "The resulting deceleration of the vehicle does not cause the brake lamps to come on." in B mode, even though on the following page it shows the rate of regeneration exceeds 1.3m/s² in most speeds.

Rectangle Slope Font Parallel Plot


And from - "Regulation No 13-H of the Economic Commission for Europe of the United Nations (UN/ECE) — Uniform provisions concerning the approval of passenger cars with regard to braking [2015/2364]", a brake signal is required beyond 1.3m/s².

Font Rectangle Parallel Number Screenshot


Will be interesting to see what comes of it - any suggestions on how to take it further?

UPDATE: Vehicle Safety Defect Report has been submitted to DVSA
 

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Good luck with this. I'm not sure that the recommendation that you quoted from ever got into law. But if Citroen say that it should work that way then there's clearly an issue.
 

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Discussion Starter · #11 · (Edited)
When was your car registered? If before July and the certification was before July 2019 then it's legal. If not it appears that Citroen have some explaining to do. It's possible that the manual is for a different generation of the car.
Car registered Jan 2021. Citroën only currently manufactures one drivetrain model of BEVs.
 

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I could only get my Zoe to bring on the brake lights up hill with regen

can’t get the pug to do it in B-mode

also the brake lights still need to be linked to the pedal for other reasons surely? Can’t just rely on g force activation

JJ
 

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Discussion Starter · #14 ·
also the brake lights still need to be linked to the pedal for other reasons surely? Can’t just rely on g force activation
The quoted regs above are purely for when using regeneration, i.e. when there is a regenerative braking effect when lifting off the accelerator it should be deceleration based. I'm fairly certain there's other regs regarding brake lights linked to the brake pedal.
 
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