Break lights during regeneration

Audi A3 E-tron Forum

Help Support Audi A3 E-tron Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

bruintoo

Well-known member
Joined
Sep 22, 2015
Messages
175
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?
 
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.
Andy
 
I'd really like to stump accross a technical article from Audi on how regenerative breaking is achieved through a dual clutch transmission.
 
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. http://insideevs.com/audi-a3-e-tron-detailed-specs/
 
Thanks!

That does not answer everything. But it's a nice clue!
I will try to investigate.
 
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 https://www.researchgate.net/public...l_Clutch_Transmission-Based_Electric_Vehicles

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!
 
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
mailto:[email protected]
 
There is so much regulation that will have to change.

Laws are always a step behind.
 
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:
 
Little off topic, but the Hyundai Sonata hybrid has a similar setup and it actually downshifts through the gears as you brake and slow down to keep the motor speed up and give nice, strong regen. It must be a hell of a software challenge to keep the braking force constant through all that, but they seem to have pulled it off perfectly. I'm assuming that Audi does the same, but who knows.
 
Yes, the e-tron down shifts through the gears as required while regenerative braking. It is most noticeable as the car comes close to a halt.
 
Dominic":9x7x23lu said:
There is so much regulation that will have to change.

Laws are always a step behind.

Current regulation doesn't actually preclude illuminating the brake lights during strong regen, but neither does it require it. At the moment, each manufacturer makes the choice. The decel effect of regen isn't much different than downshifting in a manual trans car, of course, but I expect that as with requiring added noise to plug-in cars, regulation will evolve to require brake lights illuminate at a certain regen threshold.
 
bruintoo":1n30tn38 said:
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:

My daughter was following me the other day and I called her in the car to ask about this issue. I can confirm that putting the car in manual mode and taking your foot off the accelerator does not turn on the brake lights. We didn't test Sport mode.
 
Back
Top