Audi A3 E-tron Forum

Break lights during regeneration
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Author:  bruintoo [ Thu Feb 04, 2016 12:02 pm ]
Post subject:  Break lights during regeneration

So driving in "S" sport mode in the e-tron automatically puts the car in "Hold battery" mode and with strong regeneration. If fact, one pedal driving is possible if you time it right. My question is when the car slows down during the regeneration (not pressing break pedal), do the break lights come on?

Author:  andymccrory [ Fri Feb 05, 2016 5:22 am ]
Post subject:  Re: Break lights during regeneration

I asked the same question when I got my first electric car three years ago, a Chevy Volt. The brake lights don't come on in the Chevy and I don't think they come on in the A3 either. At least in Europe, there is no requirement for them to do so anyway.

Therefore I am very careful where I use heavy regenerative braking.

In crawling traffic it is useful as you don't need to keep hunting the pedals.
In motorway driving it is useful to slow slightly without brake lights to avoid the concertina affect behind you, you would hit the brakes in an emergency anyway.
In regular driving conditions I think it's best to avoid regenerative braking and use to pedal to light up and warn following trafic that you are slowing.

In any case if you brake gently, the lights go on but the mechanical brakes don't get applied until they are needed, i.e. you need to slow more than regenerative braking will do. So you still get the regenerative benefit however you brake other than an emergency stop.

I hope this helps.

Author:  Dominic [ Fri Feb 05, 2016 6:34 am ]
Post subject:  Re: Break lights during regeneration

I'd really like to stump accross a technical article from Audi on how regenerative breaking is achieved through a dual clutch transmission.

Author:  jerry3561 [ Fri Feb 05, 2016 7:34 am ]
Post subject:  Re: Break lights during regeneration

Back in July 2014, I asked the German Audi engineers a similar question. They attempted to explain to me how it was achieved using a third clutch, I guess between the electric motor and the ICE. I'll see if I can find any diagrams on ElsaWin which might explain things.

[Edit] This is probably the best diagram I can find in the short term. It clearly shows the third clutch.

Author:  Dominic [ Fri Feb 05, 2016 7:42 am ]
Post subject:  Re: Break lights during regeneration


That does not answer everything. But it's a nice clue!
I will try to investigate.

Author:  Dominic [ Fri Feb 05, 2016 8:49 am ]
Post subject:  Re: Break lights during regeneration

I found this from a US Jetta Hydrid press release:

Regeneration and Coasting: While the gasoline engine charges the battery during non-boost states, this requires energy and thus, fuel (albeit a minimal amount). The only truly “free” way of sending charge back to the battery is through regenerative braking. This process occurs whenever the driver applies the brakes, causing the Jetta Hybrid to convert the kinetic energy (in the form of heat) generated by braking into electricity in the battery. The Jetta Hybrid increases the amount of regeneration by decoupling the engine from the drivetrain, reducing drag caused by engine braking and also increasing the amount of retardation needed (and thus heat). The engine is also shut off and is decoupled from the driveline to eliminate drag caused by the engine’s torque at higher speeds—up to 84 mph—when the driver releases the gas pedal. This helps to save fuel when, for instance, the car is going down a gentle slope or is coasting to a halt.

That offer some clarification regarding the third clutch between the ICE and the DSG.

Also here

I found some research wich suggest that a good range of rpms can be used to generate power with a variable efficiency.

My neophyte curiosity is fulfilled!

Author:  bruintoo [ Fri Feb 05, 2016 11:39 am ]
Post subject:  Re: Break lights during regeneration

Well, I got my answer.

Dear Mr. Novida,

It was great speaking with you today, and I’m happy the e-tron app is now working more reliably for you.

After further review, the brake lights will not illuminate when in sport mode and/or charge battery mode. It is my understanding that the rules and regulations set by the NHTSA in the United States wouldn’t allow for this to be possible as the brake light can only illuminate when pressure is applied to the brake pedal. However, I would be more than happy to document this recommendation for internal review by the proper parties within Audi.

As I said on the phone, if you do for some reason experience some additional concerns with the app not refreshing, please reach back out to me and I would be happy to look into this further. Thank you and have a great day!

Best regards,

Christopher Salgot
Digital and Social Media Advocate, Audi CXC

Audi of America, Inc.
Customer Experience
3800 Hamlin Road
Auburn Hills, MI, 48326
United States of America
Tel. +1 800 822 2834
Fax. +1 248 754 6521

Author:  Dominic [ Fri Feb 05, 2016 12:29 pm ]
Post subject:  Re: Break lights during regeneration

There is so much regulation that will have to change.

Laws are always a step behind.

Author:  bruintoo [ Fri Feb 05, 2016 8:32 pm ]
Post subject:  Re: Break lights during regeneration

DISREGARD THE E-MAIL POST FROM AUDI. We tested it tonight. The break lights come on when you put it on "Sport" mode, and you let go of the accelerator/gas pedal and the car goes into regeneration/recuperation without touching the break pedal at all. Who ever is following an e-tron must go nuts wondering why the guy driving a wagon keeps hitting his break pedal :lol: :lol: :lol:

Author:  Dominic [ Fri Feb 05, 2016 8:59 pm ]
Post subject:  Re: Break lights during regeneration


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