On Sat, 17 Feb 2018 12:04:58 -0800, Joerg
wrote:

On 2018-02-17 10:31, Jeff Liebermann wrote:
On Fri, 16 Feb 2018 09:27:28 -0800, Joerg
wrote:

On 2018-02-15 11:03, wrote:
Have you ever ridden or lived with a bike with electronic shifting?
I doubt it.

No but I have met a guy who had a battery fail mid-ride and then the
front DR quit. Which was just peachy in the mountainous region.

I don't see a problem:
https://www.google.com/search?q=usb++hand+crank+charger&tbm=isch
https://www.ebay.com/sch/i.html?_nkw=hand+crank+usb+charger
Or, build your own:
https://www.youtube.com/watch?v=RXmqs8DIHf8 (4:04)

You could also strap a little Honda generator onto the rear rack.

I'll assume that means you don't like the hand crank generator idea.

I have one and find it quite practical (although I've never had to use
it in a lighting emergency). It will deliver 5v at about 500ma for
furious cranking and 200ma at a comfortable rate. That's:
5v * 0.2A = 1 watt
The Shimano SM-BTR2 battery, that powers the Di2, is rated at 7.4v at
500 ma-hr:
https://www.cykelpartner.dk/shimano-di2-dura-ace-batteri-built-in-type_IBTDN1101.html
7.4 * 0.5 = 3.7 watt-hrs
It will take:
3.7 watt-hrs / 1 watt = 3.7 hrs
of moderate cranking to charge fully charge the battery. My guess(tm)
is that it will operate just fine at 25% of capacity, or about 1 hr of
cranking. Switch hands and take turns cranking the generator, and you
should be ok.

Honda doesn't make miniature gas engine models, which are usually
custom built:
https://www.google.com/search?tbm=isch&q=miniature+model+gasoline+engines
I've been thinking of grafting a PM motor as a generator onto a string
trimmer motor. However, I think a steam engine, with a boiler that
will run on either a solar concentrator or open fire, might be more
interesting.



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558