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Comment by calvinmorrison | Hacker News Reader

do we need disk brakes?

Some EV models have gone back to drum brakes. The main drawback of drum brakes is overheating, which is why they can’t be used for performance vehicles, even though drum brakes can deliver more braking power. EVs with strong regenerative braking reduces pressure on the brakes, making the heat build-up less of a problem.

The main advantage of this is cost, not weight or performance, but it does show that EVs have different profile to ICE cars.

As opposed to relying solely on engine braking (or the EV equivalent thereof)?

I'd personally prefer a belt-and-suspenders approach.

Yes, you must be able to stop independently in the case of some kind of total power failure in the drivetrain.

Can regen brakes keep a car stopped? I would think that the braking force diminishes as the rotor speed approaches zero so it wouldn’t keep you in place on a steep hill, but I’m not sure.

In my experience, it’s usually but not always enough for the hills in SF. But more importantly, regen can’t handle emergency braking (it would generate too much current and heat), and you can’t regen at all if the motor loses its path to the battery.

Good point, I guess the motor could be engaged just enough to hold the car still on a slope but there might be heat issues doing that for too long. Mechanical brake will do that easily so also needed for that reason.

At the very least you need something to keep the car from rolling away when it's parked.

well you could have really cheap drum brakes that probably would last the lifetime of the vehicle. Maybe not even hydraulic - electro-mechanical with a mechanical (E brake) fallback.

even better a motor brake already is a thing. Its kinda of like air brakes, requires current to disengage and looks liek a little clutch thats slapped on the shaft or housing.

you'd need close to a megawatt of engine/inverter to only brake on regen.

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