I've been thinking about the potential of hybrid e-bikes of this kind for a while, and I'm wondering if I'm missing a reason why it's not a more common thing. A lot of the reasons that the author of this thread laid out would really justify some of the expense in developing a miniaturised generator as a substitute for large batteries on Ebikes for certain applications.
- Lightweight petrol motors for model aircraft plus fuel, could weigh only a couple of kg, while delivering more watt hours than substantially heavier batteries.
- Even the smallest petrol motors seem to output hundreds of watts at peak power, meaning they could easily be used selectively to top up a reserve battery.
- Being able to recharge on the go could result in charging profiles which avoid battery degradation by avoiding the need to fully charge lipos.
- Additional petrol is much cheaper and easier to acquire during a journey than additional batteries, to extend range.
- Applications such as bicycle touring, bikepacking etc. are not practical for Ebike use, particularly in remote areas, but could easily be done with this kind of setup.
- As the author pointed out, regulations around power limits make attaching the petrol motor directly to the drive chain illegal in many settings.
- Range is a factor of the terrain you travel on, the weight of your bike, with rider & cargo. Many replies cited battery ranges of 100km as easily achievable. I bet I could drain that battery in 20km with some of my use cases.
The arguments against this application that stand out to me are:
- Cost; the smallest motors tend to be quite pricey.
- Complexity; there would be additional parts that could fail.
- Noise; the smaller motors aren't necessarily quiet.
- Emissions.
None of those seem to be deal breakers to me.