Question: do you want to use your bike to generate electricity and store the electricity in a battery to power a phone or other low powered appliance?

David Robertson answered on 17 Jun 2016:

I don’t cycle for long enough to charge up a phone very much. I do have a colleague who has a hub dynamo on her bike. This is a low power electricity generator built into the front wheel. She uses it to power the lights on her bike which I think is pretty neat. You only need to generate about 5Watts of power to get bright lights and even gentle cycling produces at least 100W, so powering the lights will hardly slow her down at all.