[bananabreakfast]

Because that's not how batteries work.

Regen works because the batteries are being charged by the induction of the motors taking energy from the moving car. If the batteries are full they cannot take any more change and hence cannot draw power from the motion of the car.

What do you expect them to do? Dump the current on a giant resistor and hope it doesn't melt?

[10000truths]

> Dump the current on a giant resistor and hope it doesn't melt?

That's called an induction brake and it's already widely used in trains and semi trucks. That said, you still need a friction brake at low speeds, since the induction braking force is proportional to velocity.

[LadyCailin]

Simulate the same braking curve with the physical brakes as when regen is functioning?

[dodobirdlord]

I suppose that's one approach. Mechanical brakes work by converting the kinetic energy of the vehicle into heat via friction, it seems fitting that inductive brakes would dump energy to heat by running current over a resistor. Though under normal braking circumstances I don't know what percentage of the vehicle's energy is lost to the brakes themselves and what percentage is lost to the friction of the tire with the road.

[JohnJamesRambo]

Can anyone do the math and tell me how big that resistor would need to be? I’ve always wondered how many watts are being dissipated by my brake pads and rotors when I stop.

[saagarjha]

Assuming your Tesla is around 2000 kg and traveling at 30 meters/s, it's got about 900,000 J of kinetic energy. Stopping in 10s is some serious power that you'd need to throw off.

[fulafel]

All of yhe 90 kW doesn't need to be radiated in real time though as it's ok for the brake elements to heat up.

[vagrantJin]

> What do you expect them to do? Dump the current on a giant resistor and hope it doesn't melt?

You know...they could use it to boil water for a built in coffee/green tea maker.

Just a thought...