Brake lights on when slowing in standard regenerative braking?

[dailydriver]

I assumed that the brake lights would not come on when slowing in standard regenerative braking mode, but I haven't had anyone following behind me to confirm. Noticing how quickly it can slow the car (and driving in stop and go traffic yesterday), it may be safer to have the brake lights come on when you lift off of the accelerator pedal?

I apologize in advance if this has been addressed already in another thread - I did a search and couldn't find anything. Thanks!

 

[Arnold Panz]

I assumed that the brake lights would not come on when slowing in standard regenerative braking mode, but I haven't had anyone following behind me to confirm. Noticing how quickly it can slow the car (and driving in stop and go traffic yesterday), it may be safer to have the brake lights come on when you lift off of the accelerator pedal?

I apologize in advance if this has been addressed already in another thread - I did a search and couldn't find anything. Thanks!

This was addressed elsewhere -- the brake lights come on almost as soon as regen kicks in. If you want to see when, just put on your rear camera at night and you can easily see when the brake lights come in as you lift off the pedal because the colors behind you change.

 

[mknox]

This was addressed elsewhere -- the brake lights come on almost as soon as regen kicks in. If you want to see when, just put on your rear camera at night and you can easily see when the brake lights come in as you lift off the pedal because the colors behind you change.

Slightly off topic, but I watched a video of a European test drive (might have been Norway) and it was stated that Tesla will have to disable the rear camera when the car is underway in those markets as it is against European law.

 

[Zythryn]

I took some rough measurements one night. On standard regen, brake lights came on between 10 & 15 kw of regen.
They are triggered by accelerometers when your speed slows at a certain rate.

 

[dailydriver]

I took some rough measurements one night. On standard regen, brake lights came on between 10 & 15 kw of regen.
They are triggered by accelerometers when your speed slows at a certain rate.

Thanks for the info. I figured there must be high-tech approach in this car to address this situation rather than just relying on a traditional brake pedal switch.

 

[strider]

Do brake lights always turn on with regen? (incl gap to other cars))

 

[markb1]

I took some rough measurements one night. On standard regen, brake lights came on between 10 & 15 kw of regen.
They are triggered by accelerometers when your speed slows at a certain rate.

So presumably if you are going downhill and using regen just to maintain speed, the brake lights will not come on.

 

[NeverEnough]

Will regen bring it all the way to a stop? Will the brake lights remain lit through the entire stop?

 

[strider]

Will regen bring it all the way to a stop? Will the brake lights remain lit through the entire stop?

It'll slow you down until Creep engages. Don't know what it would do if creep is off. You'll need to use the brake pedal for the last few mph and to hold yourself in place - lights will be on then. I've been driving my Roadster in heinous California bumper to bumper traffic for 2 years and never been rear-ended (I have had someone back over my nose but that's another story). So whatever algorithm they are using is working. I trust it.

 

[Arnold Panz]

Will regen bring it all the way to a stop? Will the brake lights remain lit through the entire stop?

I experimented with creep off and the car will stop, assuming you are on a flat or slightly uphill road, without touching the brake. I think the brake lights stayed on until I got slower than creep (about 5 mph). I definitely prefer creep because you end up having to hold the brake hard even on slight up hills, like an exit ramp. Plus, it feels unnatural, although I suppose one could get used to it. I didn't have a problem feather-touching the accelerator to slowly "creep" forward in traffic -- the pedal was very sensitive and responsive and I wasn't jerking it at all, but it was annoying and more work than necessary.

 

[NeverEnough]

Thanks strider and Arnold!

Perhaps I should lay off the forums for the next 6 months or there won't be any surprises left!

 

[stevezzzz]

So presumably if you are going downhill and using regen just to maintain speed, the brake lights will not come on.

This isn't something I've checked on my own car, but if the accelerometers are properly oriented the brake lights will come on when holding speed down a hill because the software will interpret the force of gravity (more precisely, the component of gravity parallel to the car's longitudinal axis) as a deceleration.

Interesting bit of related trivia: full-motion flight simulators trick pilots into believing they're accelerating by rotating the simulator cab, nose-up (while inside, the pilots are watching computer-generated visuals that tell them they're maintaining level flight).

Other semi-random thoughts: In observing my S during regen with creep disabled, I see the ammeter suddenly rise toward its zero point between 8mph and 5mph. At a dead stop with creep enabled the motor isn't pulling as it would in an ICE with auto transmission: only when you lift off the brake pedal does the software command creep torque.

 

[Sig698]

This isn't something I've checked on my own car, but if the accelerometers are properly oriented the brake lights will come on when holding speed down a hill because the software will interpret the force of gravity (more precisely, the component of gravity parallel to the car's longitudinal axis) as a deceleration.

Although I haven't checked this either, the other night I was actually thinking about this very subject. Going home down a large, popularly traveled downhill grade I did notice that all of the cars surrounding me had their brake lights on while descending and holding a constant speed. So, if the brake lights in the S do come on while going downhill and holding a constant speed, at least it won't look out of place :smile:

 

[ggr]

It'll slow you down until Creep engages. Don't know what it would do if creep is off. You'll need to use the brake pedal for the last few mph and to hold yourself in place - lights will be on then. I've been driving my Roadster in heinous California bumper to bumper traffic for 2 years and never been rear-ended (I have had someone back over my nose but that's another story). So whatever algorithm they are using is working. I trust it.

It's interesting with creep off. It will not quite stop on level road (at least in my experience). But once you've touched the brake, the creep turns off, so you can let off the brake and it won't pull forward. I like it this way. It's another example of something that is different to an ICE car, but actually better in some ways. You just have to get used to it (or turn it off, if you're not adventurous).

 

[stevezzzz]

It's interesting with creep off. It will not quite stop on level road (at least in my experience). But once you've touched the brake, the creep turns off, so you can let off the brake and it won't pull forward. I like it this way. It's another example of something that is different to an ICE car, but actually better in some ways. You just have to get used to it (or turn it off, if you're not adventurous).

@ggr: did you mean to say that tapping the brakes with creep on, while creeping, disengages creep temporarily? Interesting. If you're at a full stop with creep on and release the brakes, the car creeps, as you'd expect. Never thought to try tapping the brakes while creeping, but I'll give it a whirl next time I'm in the car and report back.

 

[stevezzzz]

@ggr, I couldn't replicate your reported behavior. With creep on, if I'm slow enough to be creeping and tap the brakes, the car continues to creep. If I come to a dead stop with my foot on the brakes, the ammeter says the motor stops applying creep torque. As soon as I lift my foot off the brake, creeping commences again.

With creep off on a flat road, lifting off the accelerator engages regen braking until the speed is below 7mph, when regen cuts out and the car coasts.

With creep on or off (it doesn't matter) regen braking (feet flat on the floor) holds downhill speed to a constant 7mph on the modest slope where I tried it this afternoon.