[petermcneeley]

When you push the 'brakes' on the an electric (or even hybrid) you simply engage the electric motor. There is a limit to how strong this form of braking can be so in certain cases you will need emergency brakes (disks or otherwise). So the brakes on an electric vehicle would be very different. I would guess in the future they wont even exist. It will just be the motors. Motors to wheels so no drive train either.

[theluketaylor]

I don't see friction brakes going away, even if it's just as as emergency backup stopping power (in the same way current friction brakes are on split hydraulic circuits for safety). I could see them being constructed differently to accommodate the fact EVs don't need friction brakes very often. A good example is VW's MEB platform uses rear drum brakes for cost and maintenance reasons. Rear brakes do very little of the actual braking, and drums are perfectly capable of stopping a car, they just suffer more fade after repeated use than discs. Since EVs don't really need to repeatedly stop with friction drums make a lot of sense.

If by 'Motors to wheels' you mean hub motors, I don't see those being a thing. That's a huge amount of unsprung mass (which affects handling and ride comfort more than 10x sprung mass). Broken wheels are also already massively expensive and increasingly common due to poorly maintained roads and automakers obsession with giant wheels and no tire sidewall. Having to replace a motor along with a wheel would be awful.

I do think we'll see plenty of one motor per wheel designs. Rivian has the pattern I think will be common: motors inboard and use small axles and CV joints. Not a very expensive setup and way fewer downsides than hub motors.

Current 4x4 designs with transfer cases, locking differentials and long, heavy driveshafts will certainly be going away. Jeep's 4xe PHEV Wranger has comically awful consumption since it retains the exact same driveline as any other Wrangler. The fact it's as aerodynamic as a brick doesn't help at highway speeds, but all the losses through the mechanical couplings hurts all the time.

[bin_bash]

Sounds to me like the brakes would be exactly the same. The wheel is connected to an axle and has a brake disc. The fact that the axle can slow the car isn't any different than exhaust braking, for example.

In case you're thinking the hydraulics would have to account for regen braking, I'm not so sure that's true. In my Tesla the brake pedal only controls the brakes. Regen braking is done by letting off the accelerator.

You can't always use regen either btw even if it was powerful enough. If the battery is too cold or is fully charged it can't be used much if at all—that energy has to go somewhere.

[theluketaylor]

We're seeing lots of competing ideas about regen braking interfaces and I'm curious which will win.

Tesla is riding hard for brake pedal == friction braking, which is certainly conceptually simple. Lift off accelerator and you get regen braking. Press brake and you get friction braking. Tesla did take away the options about regen strength (at least on my model 3) and now it's only highest. I bought my tesla this winter and it was extremely noticeable how much regen was affected by a cold battery. I had to be very careful not to assume too much regen and after a whole spring/summer/fall cycle of consistency I'm slightly worried about being too one pedal complacent.

Hyundai/Kia has repurposed steering wheel paddles to add or remove regen strength on the fly and now ionic 5 will dynamically adjust the regen using the front facing cameras to slow you down as smoothly as possible.

Most of the euro brands are all embracing D/B modes on the shifter, with D being limited or no regen and B turning it on (and often with strength settings from there).

Porsche has gone full blend, with the ability to freewheel the rear axle and only the brake pedal being used to slow down. The first amount of travel is regen only, then they slowly blend in friction brakes.

I'm sure there are other patterns out there. It's been a long time since something so fundamental to driving has been open for new concepts, so it'll be interesting to see what wins.

[bin_bash]

Yeah I've had my Tesla for a couple of years in California and even in our mild weather the seasonal differences in one pedal driving are something you have to pay attention to.

I haven't tried the other methods, they sound worse to me but perhaps I'm just used to the Tesla approach.

[b112]

Hmm. This seems quite dangerous.

In snow, if sliding starts due to braking, the best solution to regain control is to stop braking. Completely.

With manual transmission this is simple, deploy the clutch. With an classic automatic, no gas = mild drag due to engine.

But to add regen braking automatically, hmm. It means that in some circumstances, you have zero control, and the car is essentially actively working to mess up your day.

There are ways to detect slide, I wonder, does regen cease if slide is detected... just as with normal brakes and ABS studder (which doesn't reduce braking distance, but provides for steering when slide + braking)?

[theluketaylor]

Yes, regen does cut if the car detects slip (at least in Teslas)

[perl4ever]

>In my Tesla the brake pedal only controls the brakes

Are you sure about that? I have a hybrid that has paddles to adjust the deceleration resulting from letting off the gas, but using that or the brake pedal I'm pretty certain uses the regen the same way. The only difference I think is when exactly the brake lights go on.

I'm surprised if EVs are different, because it kind of applies an arbitrary semantic distinction between gas and brake pedals.

If the brake pedal only applies the friction brakes, then does that mean that moderate to heavy regen braking doesn't make your brake lights go on? That seems like a questionable design.

[theluketaylor]

Yes, the brake pedal only controls the friction brakes in Teslas. The brake lights come on when a certain amount of deceleration is achieved, not merely based on pressing the brake.

Once you stop thinking of the right pedal as 'gas' and start thinking of it as the 'accelerator' it makes perfect sense. You press down to accelerate, hold steady to maintain a speed (zero acceleration), and lift off to decelerate. The amount you press or lift off determines how much positive or negative acceleration you get. Then the brake is just there for a rare time regen isn't enough (and I go weeks without touching the brake).

[petermcneeley]

The notion of lifting up on the accelerator is a different concept in an electric car vs a combustion engine.

The energy can easily go somewhere. You can just put it through larger resistors or UltraCaps.

[bin_bash]

> The notion of lifting up on the accelerator is a different concept in an electric car vs a combustion engine.

I said the brakes are the same, not the accelerator.

[vvanders]

Not really if you've ever driven a manual transmission. Regen usually is stronger but the drive feel is not dissimilar.

[pocw]

Go look at a Tesla. The Brakes are the same as any other car. Regenerative braking kicks in first so you use it less, but it is all still there. It is exactly the same as a gas car: Same hydraulic system, same calipers, same pads, same rotors.

[Taniwha]

Depends on a bunch of things - how hard are you pressing on the brakes? above a certain threshold you're going to exceed the max current of the electrical subsystems and the traditional brakes will kick in (you don't WANT to hit that truck do you) - also once the battery is full the regen system has nowhere to dump that energy, my Prius behaves slightly differently as it switches over from regen braking once the battery is full.

[serpix]

Prius and other Toyota hybrids actually burn gasoline going downhill. Try it. Put B and go downhill and observe the consumption, the engine is on and burning gas.