Does regen braking make the brake light come on?

[mluisbrown]

I always drive in B mode which does regen braking when you lift off the accelerator (although I wish there were a more aggressive regen mode to allow true one pedal driving), and I've always wondered if when you lift off the accelerator the brake lights come on? If you're going at motorway speeds and lift partially or totally the slowdown can be significant, and certainly as much as lightly braking on a normal car. I haven't been able to verify it though. At some point I should get my wife to drive behind me in our other car to do some tests.

I was even more curious about this after watching this YouTube video about the topic:

It seems like on the Ioniq 5 the brake lights only come on if you completely lift off the accelerator, even though a partial lift can cause significant braking.

[mluisbrown]

I should have done more research before posting. On the ID.4 it looks like the brake light only comes on if you lift completely off the accelerator, a partial lift won't do it. I assume this is the same on all ID.x cars, including the Born.

[davmatjo]

The manual says that the light is based on the deceleration rate of the car. B mode isn't true one pedal driving and you could argue anything except being fully off the pedal in B mode isn't enough deceleration to warrant a brake light. You saw in that video how he still had to use the brake at the traffic lights because the deceleration in B isn't nearly enough.

As far as I know if you're in D mode you can also get brake lights without touching the brake as the car tends to automatically apply regen when it thinks you need it and no pedals are pressed. It will mostly stop you getting too close to the car in front, slow you down for roundabouts, junctions and speed limit changes, and in all these cases the brake light is applied when the deceleration is above the threshold.

[Elea4]

I'm sure the Born functions according to all legal specifications in regards to brake lights.

There are EU/UN regulations for this which VAG uses for all its vehicles:

Deceleration ≤ 0.7 m/s2: The signal shall not be generated​
Deceleration between > 0.7 m/s2 and ≤ 1.3 m/s2: The signal may be generated​
Deceleration > 1.3 m/s2: The signal shall be generated​

(UN Regulation No. 13-H Stop Lamp Illumination)

[Ponk]

Yes they come on, and from what I remember during my test, it's somewhere in the middle point of regeneration, not only when fully off the pedal. Would need to test again. Easy to do at night and look in rear view mirror.

[mluisbrown]

(UN Regulation No. 13-H Stop Lamp Illumination)

Thanks for the detailed information, as always!

If these are UN regulations then it seems odd that according to the 1st video I posted, the Ioniq 5 doesn't seem to respect them, unless the regulations are less strict in the US.