Wooh! I don't feel like such a wierdo now, suggesting "low-end" power of 750 watts or so... N obviously having both time and energy are important factors...
muffinman, dude, if yer happy round the low to mid 30kph, I reckon if you can remain road oriented, then small geared hubmotor is the go.
Here are some pics of my main GoTo bike, many trips of 40km (yeah I know, I know, that's not 100 km.. just sayiin... range on this for me is 60km)
At 47 and carrying injuries from a physically risky past
D) I am not that fit , nor young and my weight varies from 80 to 100kg with varying density.
I aim for around 30 to 32 km/hr when peddling... my average over the last 300 km has been 22... but that is a lot of urban and suburban street riding.
More human input is eminantly doable, and the fact that the hubmotor free wheels is really noticable on descents.
I am using relatively high pressure (50PSI cyclo cross tyres... kinda like an offroad tyre for road bikes
) with fairly low rolling resistance, and this bike is built for roadwork.
Some Pics
Drive side Full View
Mini Geared HubMotor
Battery and controller... Battery mount is an inverted seatpost rack that fits around the seat tube... easy on chromolly vintage... not so easy on modern larger seat tubes.
Original gears for this age bike would have been either on the stem or downtube. Although stiff, these cheapo shifters work.
Th throttle has had the standard battery level light and on off switch cut off to clear the shifters.
As luck would have it I hade a dd 250-1.2kw rea drive nearby laced in a 26" rim, giving good size comparison
Human and Electric drive chain
This build uses a 250w/36v rated no-name brand/Cohnis geared mini hub motor laced into a 700c rim.
The controller is a 10ah controller purty much the same as yescomusa sells, modified from 20 amps to 10 amps
The battery is a nominal 48v 10ah Lipo Pack (4* 6s 5ah in a 12s2p configuration for 12s 10ah)
Max wattage for this motor in this configuration is around 700 watts
Max speed on the flat in ideal (no headwind, smooth surface) conditions is around 35km/h
The base bike is a vintage (early 80s) Crome Molly steel road racer.
all the parts/componets I reckon you could source for $500 (cheaper if you are willing to do your own bike building and source of craigslist or woteva and probably cheaper in US dollars (I am thinking in AUS$))
NOTE: I have a cycle analyst mounted but it is not necessary,, a $20 wattsup meter and a 10 dollar cycle computer/speedometer provides all the data you need for day to day running.
I reckon 15ah, better yet 20 ah battery capacity would be the go... Not impossible that you only NEED 15ah if you truly are going to be grinding it out on the pedals.
Personally I don't think you can go past Lipo for cheapness and size, and srsly if you look after it, nothing beats it in my opinion...
15ah at 12s costs about 300 AUD, plus another $100 for charger and power supply and a meter...
For US1000 dollars I reckon you could get yourself something that could do the job...
Opinions may vary
and this is just an example of what you can do with lighter builds that can work if you want cyclist speed assist.
Joe