Originally Posted by
noglider
What are you hoping to accomplish? A few people use dynamos on their bikes to charge their electronics, but it doesn't seem worth the expense unless you're going to ride many days with a lot of time away from a power outlet. I use an Anker external battery to keep my phone charged while I'm on the bike. I'm at a power outlet every night.
I just was looking into this for a tour we're planning next summer. I came to the conclusion that it's a lot easier to find a small but high power density USB-C adaptor and locate the occasional outlet to charge my battery. All of these dynamos put out ridiculously low power. It's a significant time to just charge your phone. And this was in looking at it as if money weren't an object, but just for feasibility. When you add in the cost of the system (dynamo wheel), then the choice is obvious - go with the battery and hunt for outlets.
Originally Posted by
andy_p
I'm just thinking about this as a design exercise. Given that current solutions for charging larger devices (a phone, battery pack, etc) are expensive and less than ideal due to the issues already outlined (wide range of operating rpm, relatively low power output available, considerations for existing lighting systems, etc), what would a more ideal solution look like? I had the thought that a separate generator, driven by a front chainring, would alleviate most of these issues. It would largely operate within a small rpm range, could be sized for more output power than dynohubs, and wouldn't need to share its output with lighting systems.
The main problems I see are: difficulty of mounting (it would have to mesh with the smallest chainring, on the unused portion towards the rear of the ring), the small amount of available space, and weatherproofing.
The problem is going to be that (a) you need a LOT more power, maybe a consistent 10-15W output and (b) cyclists generate motion with surprisingly little power and as such, can't tolerate much of a power loss going to the tire. Even if you could get 100% efficiency, that 10-15W would probably be uncomfortable quickly in a number of situations. Ultimately, solar is probably going to be better power "bang" for the buck, I'd guess.
J