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Not really, even in this hypothetically perfect scenario. Either the hill isn’t steep enough to generate any real excess energy from rolling down it (too much drag and you’ll stop rolling) or it’s steep enough that what you collect is offset by how much energy the ride home requires. The more potential energy you save for later, the slower you’re traveling now. And you can never cross the threshold to where it’s helpful. You’re trying to steal energy from a closed loop. It’s the “bowling ball dropped from face level” problem all over again. It can never get enough potential energy from its trip away to come all the way back.

Storing pedaled energy is pointless too.

Let’s say one regular old pedal rotation propels you 10 feet.

Let’s instead store 20% of that energy for later. You now only travel 8 feet.

While we’re converting that energy, we lose a quarter of it due to inefficiencies in the process. So now we’ve traveled 8 feet and stored 1.5 potential feet.

Pedal 1000 times. We go 8000 feet and store 1500 potential feet. Stop pedaling, turn on battery support, we go 1500 feet, we get 9500 total. 500 less than an unmodified bike. That’s excluding additional system inefficiencies like the added weight of the modifications and the mechanical efficiency of the pedal assist. It’s more efficient to just pedal.