When do brake lights come on..?

Yup, they are. Try at night sometime with your lights facing a building so you can see the light reflected off the surface. Even a slight application will light 'em up.

 

Each car is slightly different, mikewithaprius' suggestion is best, check your own particular car (this is something we should all do from time to time anyway, to ensure all our brake lights are working correctly.)

 

Strange question. There can't be any regen until the brakes start slowing the car.

 

The brake lights are activated by a mechanical switch on the brake pedal arm. They come on anytime the pedal is depressed. The actuation point can be changed by adjusting the switch mounting bracket.

Tom

 

Hey jburns, I think he means it's a fairly steep hill. There's one I drive on where if let up on the accelerator I get a nice almost 20 amps into the battery, but my speed stays constant (instead of increasing like gravity wants it to).

 

In that situation you don't get brake lights, nor should you. The regenerative drag from lifting off the gas simulates engine drag. No car shows brake lights for engine drag because the driver isn't braking.

Tom

 

Tom, I think he's pressing on the brake too, not just lifting off the gas. I think your first response was correct.

I think the suggestions of the OP checking for himself are the way to go - either on this regular downhill at night with no traffic around (if possible), since the brake lights should be visible reflecting off the dark surroundings; if that isn't feasible, then just leave the car in park just in front of something (a wall, eg) and start pressing on the brake pedal. When you can see the brake lights reflecting off the wall, you know how much pedal travel is needed before the brake lights turn on, which is the same whether you're moving or not. It's typically more than a very very light touch, but you don't need to push very far.

And if it's not sensitive enough for you, try a search here on how to adjust it - I suggest searching for somebody who's looking to make canceling cruise control more sensitive, as that's the usual reason for doing so (and the same switch that cancels cruise control with the brakes is the one that lights up the brake lights).

In fact, that brings up another way you could test this; set the cruise control, then start pressing on the brakes. When it takes you out of cruise, you know you tripped the brake light switch.

 

I am curious if the brake lights come on when the radar cruise control somewhat abruptly slows the car. I notice that the cruise control also applies a good bit of braking descending a hill if speed goes over 2 mph above "set" speed.

 

If the cruise control only reduces throttle, then there are no lights. If brakes are applied you get lights.

Tom