EV-specific trailers incoming!

[SwampNut]

If it is decelerating but doesn't need to brake, why turn on the brake light ?

Regenerative braking is braking. If you hold neutral throttle or even very slight deceleration, no brake light. Move your foot off, and the lights come on. It has to be this way for the ICErs around you. They don't expect regeneration. Same reason they teach motorcyclists to flash a brake light if they go off throttle, as bikes have great engine braking.

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[WildhavenMI]

Maybe a minor concern - but is there a single EV on the road today that will actually go into drive while being charged? How is the actual battery in the trailer going to be of benefit if I have to pull over to draw from it?

 

[Ogre]

Does anyone know if a Tesla with a brake controller will start to apply the normal trailer brakes as soon as the brake lights come on? I think it might. Which wastes a lot of power. Wonder if it could more intelligently delay braking until you actually press the car's brake pedal?

I’m not sure. I don’t think it engages the trailer brakes immediately b

Does a Tesla always activate the brake light when you take your foot off the accelerator?

-Crissa

i think so. I slows down fairly aggressively.

trailer Mode might change things a bit.

 

[JBee]

Regenerative braking is braking. If you hold neutral throttle or even very slight deceleration, no brake light. Move your foot off, and the lights come on. It has to be this way for the ICErs around you. They don't expect regeneration. Same reason they teach motorcyclists to flash a brake light if they go off throttle, as bikes have great engine braking.

Even the Prius shows brakes lights whilst regening without the brake.

I think there's rules around how much deceleration should show braking light.

 

[firsttruck]

Maybe a minor concern - but is there a single EV on the road today that will actually go into drive while being charged? How is the actual battery in the trailer going to be of benefit if I have to pull over to draw from it?

A charging station you haul with you. If there are no stationary charging stations around, carrying your own might be only option if you really want to get to some locations.

ICE off-roaders might carry a couple jerry cans of extra gas. They usually stop to fill-up with this extra fuel tho some might risk other methods.

 

[Bill906]

Does a Tesla always activate the brake light when you take your foot off the accelerator?

-Crissa

I’ve asked this question before, I assumed it was on this forum, but maybe not. The vehicle knows it’s accel/decel rate at any given time. If it detects a decel rate greater than x, it turns the brake lights on. I don’t remember who or where I heard that, but it made sense to me. I’d guess the trailer brake signal would work similar.

 

[Bill906]

Even the Prius shows brakes lights whilst regening without the brake.

Do Priuses (Prii?) do some degree of single pedal driving? My 2009 Ford Escape Hybrid did virtually no regenerating when your foot was off the accelerator and brake pedals. It coasted just like most other automatic transmission ICE vehicles. When you pressed on the brake pedal it would trigger a mix of regen and mechanical braking automatically based on things like how hard you’re pressing, your speed, battery level etc. It worked flawlessly except when the brakes got wet. Leaving the car wash there was a notable jerk (other than me) when I stopped as the brake system recalibrated for the slippery pads. Nothing outrageous, just a big of a jerk at a slow speed coming to a stop.
Before buying the Escape Hybrid I did some research on it. One of the main objectives was to make it act just like it’s non-hybrid version. Personally I wish they would have given me more control over it. I would have loved to be able to put it in pure electric mode. Instead, I’d learned how to accelerate slowly enough to keep it in electric mode for as long as possible.

 

[Crissa]

Regenerative braking is braking. If you hold neutral throttle or even very slight deceleration, no brake light. Move your foot off, and the lights come on. It has to be this way for the ICErs around you. They don't expect regeneration. Same reason they teach motorcyclists to flash a brake light if they go off throttle, as bikes have great engine braking.

That makes Tesla the only one that does that, that I know of. Which is much safer, I know.

I have to touch the brake to get a brake light on my Zero. Same for an Energica or Livewire. It's a button on an Arcimoto, so they get lights. And on any ICE vehicle, well, you don't get lights when engine braking or coasting.

-Crissa

 

[Ogre]

That makes Tesla the only one that does that, that I know of. Which is much safer, I know.

I have to touch the brake to get a brake light on my Zero. Same for an Energica or Livewire. It's a button on an Arcimoto, so they get lights. And on any ICE vehicle, well, you don't get lights when engine braking or coasting.

-Crissa

Not sure about the other EVs, but it’s definitely much more aggressive braking than coasting to a stop. I think even from 60MPH you’d slow to a stop fairly quickly. Not like stabbing the brakes on an ICE car, but enough where an unsuspecting driver in an ICE car might think you were braking.

 

[Crissa]

I've nearly hit people engine braking hard, so there's that. So I always hit the brakes when I hard regen, at least to make the lights come on.

-Crissa

 

[Ogre]

I've nearly hit people engine braking hard, so there's that. So I always hit the brakes when I hard regen, at least to make the lights come on.

-Crissa

I do wish it was controllable though. There are definitely situations where I’d prefer to coast. Also, if the trailer brakes kick on any time the vehicle brakes are on, that’s not great. My preference would be trailer brakes on kick on when the actual brake pedal is pushed.

Not 100% sure how it works though.

 

[Crissa]

Definitely.

The brakes only automatically come on at the very end of a stop, using one-pedal driving, in a Tesla. That I do know ^-^ And that is a setting - the creep or no creep option.

-Crissa

 

[Bill906]

Definitely.

The brakes only automatically come on at the very end of a stop, using one-pedal driving, in a Tesla. That I do know ^-^ And that is a setting - the creep or no creep option.

-Crissa

Does the car apply the friction brakes when stopped in One pedal driving mode? I just assumed they held the motors at zero speed.

 

[SwampNut]

Does the car apply the friction brakes when stopped in One pedal driving mode? I just assumed they held the motors at zero speed.

Friction brakes are applied from around 5 MPH (my estimate not truly documented that I can find). Electric motors have very little friction at low speeds. "Holding" a motor consumes power. For example, I've measured the anti-theft e-brake on one of my electric bikes at over 700 watts. Without that, the motor just spins.

Any electric car with regenerative braking that doesn't turn on the brake light is absolutely stupid. I wish motorcycles were smarter about it with engine braking. I put a "Smarter Signal" module on my KTM 390 Adventure which does flash and turn on the brake light on deceleration. Wife commented that the aggressive engine braking was going to get me killed, one day while following me.

 

[Bill906]

Electric motors have very little friction at low speeds. "Holding" a motor consumes power. For example, I've measured the anti-theft e-brake on one of my electric bikes at over 700 watts. Without that, the motor just spins.

With a decent inverter, motor feedback, and the motor sized for the application, you can control an electric motor at any speed. I'm not sure what you mean by "Electric motors have very little friction at low speeds."

Depending on how they hold the motor depends on how much power the motor consumes. The easy way is simply apply a DC current (0Hz) at a fixed current amount to the motor, although that is the easiest way, that method is wasteful. If instead they are holding zero speed with a regulator, the amount of power would be proportional to the amount needed. Holding the vehicle in place on a hill would use more power than on a flat surface. I have played with a 1HP induction motor and a well tuned inverter. I commanded the inverter to hold zero speed and the motor shaft felt like it was welded to the motor.

I'm not saying Teslas don't engage the friction brake, I do not know. They probably do. The only reason I would think they wouldn't is that it's tricky to get the transition from held by brake to controlled by motor to be a smooth one. But not impossible, so I agree that is likely what they do, but again, I do not know.

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