eCue wrote: ↑
Jan 06, 2018 3:22 pm
With that said it would take a 1/2 gallon of gas to charge 1 battery !!! At that point might as well buy a moped and skip the charging losses.
Really? So that got me thinkin ...
There are about 32 KWh of power in a gallon of gasoline. So 16 KWh for a half gallon. Typical internal combustion energy efficiency is about 20% (a small engine is probably average or less), so that leaves only about 3.2KwH produced at the motor hub. Since electric motors can be over 80% efficient, I'm going to assume a similar efficiency for an electric generator. At 80%, that leaves around 2.5KWh of energy for charging a battery. That's still a pretty big battery (30 + pounds?) - one that should give you a range of about 100 miles on a typical ebike at around 20+ mph. Less with a trailer or lots of cargo of course. Is your battery actually that large?
Grid power is typically about twice as efficient as a portable generator. I'd assume that portable generators have lousy emission characteristics as well. I can see how hauling a small generator could have practical value in some situations, but it does seem to work against the "small footprint" notion that many ebikers tend to embrace. But then I haven't tried to quantify the impacts of the manufacturing of any of these things either. Though all of these things are surely substantially less impactful per WH than human based power sources. :^)
(Side note - I wonder about the viability of direct mounting a small gas engine that would drive the direct hub equipped wheel on an ebike and use that direct drive motor as a generator. That would seem to be one of the lightest approaches ... and also puts us closer to being a moped.)
"Commuter - DC Booster"
Iron Horse 3.0 hardtail - 48V / 1000W / 470rpm generic Chinese DD Hub motor (ebay)
8 x 36v 4.3ah 10s 2P battery packs - 1500W 30A DC Boost Converter delivers 54v and about 1000 watts peak
53T/42T Sakae Road cranks - 30mph+ on flats