No brake llights above 136 kph (85 mph) while using regen braking

[slcuervo]

I just received some inputs from someone who watches my YouTube channel in Spanish.

He owns a Mercedes C180 and tested the deceleration from 150 to 140 kph.

That took 2,5 secs in my Model S with regen braking.

He took 6,2 secs in 6th gear, 5 secs in 5th gear and 3,9 secs in 4th gear.

I know not all ICEs will decelerate at the same rate, since it will depend on engine power, drag, etc.

But for those who stated that brake lights are not needed under the circumstances I described, do these figures make you change your point of view?

 

[sillydriver]

I just received some inputs from someone who watches my YouTube channel in Spanish.

He owns a Mercedes C180 and tested the deceleration from 150 to 140 kph.

That took 2,5 secs in my Model S with regen braking.

He took 6,2 secs in 6th gear, 5 secs in 5th gear and 3,9 secs in 4th gear.

I know not all ICEs will decelerate at the same rate, since it will depend on engine power, drag, etc.

But for those who stated that brake lights are not needed under the circumstances I described, do these figures make you change your point of view?

Yes they do.

 

[AWDtsla]

I just received some inputs from someone who watches my YouTube channel in Spanish.

He owns a Mercedes C180 and tested the deceleration from 150 to 140 kph.

That took 2,5 secs in my Model S with regen braking.

He took 6,2 secs in 6th gear, 5 secs in 5th gear and 3,9 secs in 4th gear.

I know not all ICEs will decelerate at the same rate, since it will depend on engine power, drag, etc.

But for those who stated that brake lights are not needed under the circumstances I described, do these figures make you change your point of view?

No. First of all you're comparing to a car that has a 1.6 liter 150bhp engine? Try comparing to an BMW M3 or M5 in 4th gear. Projecting from the figures you have, I would almost expect those cars to have more deceleration, especially considering the the aerodynamic advantage the Model S has.

There is no legal or technical deceleration limit at which brake lights are supposed to come on. In fact, I'm fully thinking about a brake light defeat switch, because frankly if you're flashing brake lights all the time on the highway you look like a moron and are causing even more traffic behind you due to overbraking behind you.

 

[slcuervo]

Well it is all about the amount of deceleration after all. I would love to compare the Model S deceleration under full regen at those speeds to that of cars with much powerful engine than the MB C180K but I just don't know anyone with those cars.

Maybe you guys could help?

I am basing my assumptions (that the brake lights should go on) on what I have observed driving in Germany at high speeds, i.e. that when following other cars and approaching slower vehicles they had to decelerate using brakes while I did not because deceleration from full regen was powerful enough.

So they had brake lights on and the Model S did not.

But anyway, until someone can feed us with some deceleration figures from a powerful ICE, we'll be just exchanging perceptions and opinions, I guess...

 

[MrJones390]

I could slow down (pretty fast) from 120mph to almost a stop with no brake lights in my manual WRX simply by downshifting. It's only a safety hazard if the person behind you is making it a safety hazard.

 

[woof]

There is no legal or technical deceleration limit at which brake lights are supposed to come on.

See UN Vehicle Regulation 13H, section 5.2.22.4:

5.2.22.4. Electric regenerative braking systems as defined in paragraph 2.17. of this Regulation, which produce a retarding force upon release of the accelerator control, shall generate the signal mentioned above according to the following provisions:

Vehicle decelerations	Signal generation
≤ 0.7 m/s²	The signal shall not be generated
> 0.7 m/s² and ≤ 1.3 m/s²	The signal may be generated
> 1.3 m/s²	The signal shall be generated

In all cases the signal shall be de-activated at the latest when the deceleration has fallen below 0.7 m/s².

http://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/updates/R13hr3e_.pdf

 

[AudubonB]

See UN Vehicle Regulation 13H, section 5.2.22.4:

Holy New World Order! That's fusty stuff. Who's signatory to it?

 

[woof]

Holy New World Order! That's fusty stuff. Who's signatory to it?

BTSOM. Probably whomever wants to sell electric cars to the UN!

 

[slcuervo]

I could slow down (pretty fast) from 120mph to almost a stop with no brake lights in my manual WRX simply by downshifting. It's only a safety hazard if the person behind you is making it a safety hazard.

The question is: did you slow down faster, as fast as, or slower than a Model S?

I bet slower

 

[MrJones390]

Have you ever downshifted in a stick shift?? It's way faster.

 

[slcuervo]

I live in Europe, manual gearbox is the most common, and yes I have. Only 2 of all the cars I've had were automatic.

The matter is not transmission or gears, which you apparently perceive as being ultra effective slowing down cars, but deceleration.

You can have a stick shift car with a very small 1.2 gasoline engine and low drag, with a terrible deceleration as a result.

If someone can get deceleration figures from ICE cars that they believe slow down more than the Model S, that would really add to this thread.

Thanks!

 

[Daniel 74]

I don't think 2.5 seconds to decelerate from 150 to 140 km/h justifies braking lights turning on, on the contrary.

 

[slcuervo]

I don't think 2.5 seconds to decelerate from 150 to 140 km/h justifies braking lights turning on, on the contrary.

Even knowing that any ICE car undergoing such deceleration would have to use its brakes and therefore would have its brake lights on?

 

[rdrcrmatt]

... just saw this thread..

how is this a problem? I don't see it. EVERY car will decelerate rather quickly from high speed if you just take your foot off the throttle. The Model S only turns on the brake lights during regen if the rate of deceleration is greater than a threshold. Perhaps 60kw of regent at high speed doesn't reach that threshold.

Not a problem IMO.

 

[slcuervo]

... just saw this thread..

how is this a problem? I don't see it. EVERY car will decelerate rather quickly from high speed if you just take your foot off the throttle. The Model S only turns on the brake lights during regen if the rate of deceleration is greater than a threshold. Perhaps 60kw of regent at high speed doesn't reach that threshold.

Not a problem IMO.

Because I suspect, and I am trying to gather data to show this, that the Model S decelerates much more than other cars, just as if you were using brakes in an ICE car. And therefore it is safer to let others know by using brake lights. Just the same as under 136 kph.

 

[rpo]

I tried this out the other day. From 115 mph to ~90 with my foot completely off the accelerator, there were no brake lights despite slowing rapidly. I don't mind one bit.

 

[slcuervo]

I tried this out the other day. From 115 mph to ~90 with my foot completely off the accelerator, there were no brake lights despite slowing rapidly. I don't mind one bit.

Does your Model S have autopilot?

 

[rpo]

Does your Model S have autopilot?

No. Does that make a difference?

 

[slcuervo]

No. Does that make a difference?

It supports my belief that it is a software bug. Autopilot cars do have brake lights above 85 mph under the circumstances I have described, but non AP do not...

 

[Cottonwood]

It supports my belief that it is a software bug. Autopilot cars do have brake lights above 85 mph under the circumstances I have described, but non AP do not...

My autopilot car contradicts your theory.

I posted earlier, that with reduced regen, I do not see brake lights at correspondingly lower speeds. My car is an autopilot P85D and does not show the brake lights until the speed is slow enough to produce regen force that is comparable to light braking.