Debate regarding braking, regen, and brake light illumination.

[jwrezz]

Following. I know I have used OPD since I got the truck 3 weeks ago. Very interesting conversation. I may have to try the different modes.

Sponsored

 

[mattskr]

ChatGPT 5 surprised me because it's usually wrong but I actually think this is the correct answer. Who knows, maybe some intern at Ford copied the actual technical document into ChatGPT to get a summary of it and now it's part of its training data

In 1-Pedal Drive mode, the Lightning primarily uses regenerative braking to slow the truck down. That means the electric motors act as generators, converting kinetic energy back into electricity and sending it to the battery.

However:

• If you demand more deceleration than regen alone can provide (for example, in a hard stop, steep downhill, or when the battery is near full and can’t accept much charge), the truck blends in the physical friction brakes automatically.
• At very low speeds, regen effectiveness tapers off, so the Lightning uses friction brakes to bring the vehicle to a complete stop and hold it there.
• The handoff between regen and friction is seamless — the driver doesn’t feel a sudden transition.

So, short answer:
In most normal slowing and stopping, the Lightning relies almost entirely on regen in 1-pedal mode.
But yes, it will use the friction brakes when regen isn’t enough or at very low speeds.

On the F-150 Lightning (and most EVs with one-pedal driving), the brake lights aren’t tied only to the physical brake pedal — they’re controlled by deceleration level.

Here’s how it works:

• When you lift off the accelerator in 1-Pedal Drive, the truck starts slowing with regenerative braking.
• If the rate of deceleration is high enough (roughly similar to what would happen if you pressed the brake pedal lightly), the brake lights automatically come on — even if you never touch the brake pedal.
• If the regen is very gentle (like easing off on the highway), the brake lights may stay off.
• At very low speeds, when regen blends into friction braking to bring the truck to a stop, the brake lights remain illuminated until you accelerate again.

This is done so that drivers behind you can anticipate your slowing, regardless of whether it’s regen or friction braking causing it.

In short:
The Lightning’s brake lights illuminate any time the deceleration exceeds a set threshold, whether that’s caused by regen, friction brakes, or a mix of both.

 

[mr.Magoo]

In short:
The Lightning’s brake lights illuminate any time the deceleration exceeds a set threshold, whether that’s caused by regen, friction brakes, or a mix of both.

While not incorrect, it could also be misunderstood.

The brake pedal still have a switch.
So the brake lights will light up no matter what your deceleration is, if you use the brake pedal.

 

[Firn]

the truth is not always what you assume.... TEST IT.

You have been proved wrong on this so many times now I think YOU need to test it. I know that I HAVE tested it, we have even shown you the video evidence OF it being tested, I MADE those videos.

And to be perfectly clear, because you continue to be confused by regen as well. REGEN is short for Regenerative braking, using the electric motors to slow the vehicle down. REGEN is THE method, and the only method, the truck uses to slow in one-pedal mode, friction brakes are NOT employed other than the last few feet before coming to a complete stop.

 

[Firn]

ChatGPT 5 surprised me because it's usually wrong but I actually think this is the correct answer. Who knows, maybe some intern at Ford copied the actual technical document into ChatGPT to get a summary of it and now it's part of its training data

In 1-Pedal Drive mode, the Lightning primarily uses regenerative braking to slow the truck down. That means the electric motors act as generators, converting kinetic energy back into electricity and sending it to the battery.

However:

• If you demand more deceleration than regen alone can provide (for example, in a hard stop, steep downhill, or when the battery is near full and can’t accept much charge), the truck blends in the physical friction brakes automatically.
• At very low speeds, regen effectiveness tapers off, so the Lightning uses friction brakes to bring the vehicle to a complete stop and hold it there.
• The handoff between regen and friction is seamless — the driver doesn’t feel a sudden transition.

So, short answer:
In most normal slowing and stopping, the Lightning relies almost entirely on regen in 1-pedal mode.
But yes, it will use the friction brakes when regen isn’t enough or at very low speeds.

On the F-150 Lightning (and most EVs with one-pedal driving), the brake lights aren’t tied only to the physical brake pedal — they’re controlled by deceleration level.

Here’s how it works:

• When you lift off the accelerator in 1-Pedal Drive, the truck starts slowing with regenerative braking.
• If the rate of deceleration is high enough (roughly similar to what would happen if you pressed the brake pedal lightly), the brake lights automatically come on — even if you never touch the brake pedal.
• If the regen is very gentle (like easing off on the highway), the brake lights may stay off.
• At very low speeds, when regen blends into friction braking to bring the truck to a stop, the brake lights remain illuminated until you accelerate again.

This is done so that drivers behind you can anticipate your slowing, regardless of whether it’s regen or friction braking causing it.

In short:
The Lightning’s brake lights illuminate any time the deceleration exceeds a set threshold, whether that’s caused by regen, friction brakes, or a mix of both.

There is one caveat to this. It does not illuminated the brake light in two pedal drive mode, even in Sport. Typically it wouldn't deceleration hard enough for it to be an issue but I have tested this going downhill with cruise set at a lower speed and suddenly releasing the accelerator. The deceleration rate should well exceed the brake light threshold but it does not cause the brake lights to illuminate.

 

[RLXXI]

ChatGPT 5 surprised me because it's usually wrong

• If the rate of deceleration is high enough (roughly similar to what would happen if you pressed the brake pedal lightly), the brake lights automatically come on — even if you never touch the brake pedal.
• If the regen is very gentle (like easing off on the highway), the brake lights may stay off.

It still IS wrong lol. I posted above that the brake lights come on immediately in 1PD mode just barely lifting my foot partially off the pedal. When I say immediately, I mean instantly, right now, no waiting. Not even enough regen working to slow the truck and the brake lights came on.

 

[RLXXI]

There is one caveat to this. It does not illuminated the brake light in two pedal drive mode, even in Sport. Typically it wouldn't deceleration hard enough for it to be an issue but I have tested this going downhill with cruise set at a lower speed and suddenly releasing the accelerator. The deceleration rate should well exceed the brake light threshold but it does not and the lights do not illuminate.

Exactly my experience as well.

 

[mr.Magoo]

It still IS wrong lol. I posted above that the brake lights come on immediately in 1PD mode just barely lifting my foot partially off the pedal. When I say immediately, I mean instantly, right now, no waiting. Not even enough regen working to slow the truck and the brake lights came on.

At this point I suppose we're splitting hairs, but at least on mine it's definitely not "immediately" or "barely lifting"

I can easily slow down at a stop light without the brakelights coming on until the very end, maybe from 45 to 15 without and 15-0 with brake lights and that at a rate you can feel in your body, around 1/2" green on the acc/dec meter.

It gets more sensitive the slower you go, so yes, at 10mph I'd agree with "barely" but at 45+ you can definitely feel it.....

 

[Henry Ford]

The brake lights come on at a certain deceleration rate (1.3m/s2 in EU, manufacturer choice in US) or brake pedal application. If you aren't pressing the brake pedal there isn't a reliable way to determine if friction brakes are in use.

I wrote this in post #7. It's still true. I'll even go out on a limb and say Lightning brake lights come on at a deceleration rate of 1.3m/s2 or brake pedal application since they sell EVs in Europe and it would be an enormous waste of money to develop two standards.

 

[RLXXI]

At this point I suppose we're splitting hairs, but at least on mine it's definitely not "immediately" or "barely lifting"

I can easily slow down at a stop light without the brakelights coming on until the very end, maybe from 45 to 15 without and 15-0 with brake lights and that at a rate you can feel in your body, around 1/2" green on the acc/dec meter.

It gets more sensitive the slower you go, so yes, at 10mph I'd agree with "barely" but at 45+ you can definitely feel it.....

They may have changed operating strategy between your 22 and my 25, all I can do is report what I'm experiencing.

 

[RLXXI]

I wrote this in post #7. It's still true. I'll even go out on a limb and say Lightning brake lights come on at a deceleration rate of 1.3m/s2 or brake pedal application since they sell EVs in Europe and it would be an enormous waste of money to develop two standards.

Not in my case, perhaps they changed parameters between the 22 and 25 year models.

 

[Firn]

The brake lights come on at a certain deceleration rate (1.3m/s2 in EU, manufacturer choice in US) or brake pedal application. If you aren't pressing the brake pedal there isn't a reliable way to determine if friction brakes are in use.

Carscanner has a PID for brake line pressure. I verified that 1pd drive does not use friction brakes, not until the last 1mph or so to come to a complete stop.

 

[Joe.....Montana]

I'm just hoping there aren't any physics professors around...because this thread would get real heated with the term "deceleration" being thrown around...

 

[Henry Ford]

I'm just hoping there aren't any physics professors around...because this thread would get real heated with the term "deceleration" being thrown around...

Everyone else would be confused if the term "negative acceleration" was used.

 

[Joe.....Montana]

Everyone else would be confused if the term "negative acceleration" was used.

What about acceleration in the opposite direction?

Sponsored