Afaik almost all ebikes do not have regen. If it's a hub motor it's often geared with a one way bearing, and if it's mid drive (getting more popular) then you cant have regen as the chain is not back-drivable.

The efficiency gains of bicycle regen is not high enough and there is added drag of pulling a motor along if you are just pedalling normally. Most regard the trade-offs to be not worth it.

There is one Canadian ebike parts manufacturer that's pushing for regen, and their main reason for doing so is that it saves on brake pad wear.

I’ve had an ebike that had regen (Stromer ST2). It wouldn’t have any effect on the battery, but was great for savings life of your brake pads

I suspect that is correct. There just isn't that much available energy to recover in most bike stops. The point about brake pad wear however is more relevant than you might expect. Bike brakes can be surprisingly expensive and on my e-bike I went through a full set in only 700 miles.

Of course there is the minor problem that the hub was mounted in the rear wheel so it's only good for gentle to moderate braking, but thankfully that is the vast majority of what you do.

I don't know if my ebike has regen or not, but if doesn't, it must be dumping that energy as heat somewhere. With the battery connected, the motor is breaking the bike. With the battery disconnected, the bike rolls as freely as a normal bike. It's very noticeable.

Yeah it’s just heat. Some e-bikes have a clutch to disengage the motor to prevent this motor breaking.

Wouldn't it be much simpler to disengage the battery electrically than a physical clutch? Or is the "clutch" just an electronic?

And where is the heat dumped? Why does the physical resistance disappear when the battery is disconnected?

There are some scooters with regen I think. At least I've seen scooter motor controllers with that option. I'm not sure if it's worth it. Maybe in hilly landscape.

> Can't you still run it downhill and regain energy?

That just means you had stored potential energy, otherwise how are you going to get up the hill?

I'm not sure what you mean? You need to get up the hill to get down the hill, but today when I do that the energy downhill gets wasted through heating of my brakes at the bottom. If I could use that energy for easier time the next hill around that'd be really nice.

On moderate descents a bike reaches equilibrium with the air resistance at a low speed, so there's nothing to recover.