A stationary bike I can ride at night to charge up my e-bike so I can ride to work in the morning and not arrive to work sweaty, but still know I put in the effort.
From r/Lightbulb · originally by u/KingBooRadley · February 15, 2026
Proposals
Suggest features, requirements, or refinements. Vote on what matters.
Log in to suggest a feature.
No proposals yet. Suggest a feature to get started.
Discussion(3)
Questions, clarifications, and general conversation.
Log in to join the discussion.
It would need to plug into power because it's not very efficient, but it certainly is doable. It would be like an exercise bike that turns on your charger when you're pedaling.
You’d lose a good percentage of the energy in conversion inefficiencies. It may be easier to measure how much effort you put in and charge the e-bike by the same amount using electricity from the grid. The monetary value of the energy you generate by pedaling will be trivial (3 hours of intense pedaling will be like 1 kWh, worth about 15 to 25 cents depending on time of day, jurisdiction, etc.) But your idea has more elegance to it.
What about a setting on the e-bike itself which would turn the motor into a dynamo? Then you'd only need a way to securely prop up the back wheel rather than an entire second bike.