A picture's worth a thousand words...
So, here's a picture of my e‑bike of choice, a Reise & Müller Charger ‑ the Nuvinci/Gates beltdrive variant
Reise & Müller bikes are said to be the best of the best... Reise & Müller are a relative new‑comer to the e‑bike scene (starting in 1993) and the bikes, these days, are made in Darmstadt, Germany
My 2014 model is by now a couple of generations of technology behind, but even so, it's still a formidable bike with a mid‑mounted 250W Bosch Performance Line electric motor (400Wh/36V), NuVinci N360 continuously variable rear hub transmission and a Gates Carbon Drive belt rather than the usual bike chain.
The workings of the rear hub totally elude me but it's low maintenance and has really easy, intuitive operation. Unlike a derailleur gear which relies on a jumping chain to change, the gear change occurs within the rear wheel hub and doesn't require you to be pedalling when you change and allows you to smoothly switch to an endless number of continuous gears within a gear range of 360% And perhaps best of all for touring, an internal hub is a closed system so the gears are protected from moisture and dirt at all times.
The Gates carbon belt drive has the advantage of even less maintenance (and grease) than the more usual chain, plus it's especially quiet.
A full charge takes about 3.5 hours and is good for a range of up to 130 kms ‑ of course the range is almost entirely dependent on the 'power setting' selected. There are 5 levels of assistance ‑ the electric motor doesn't replace pedalling effort, it just adds power proportional to the effort made by the rider (at least up to 25 km/h cos the bike is speed limited to 25 km/h) ‑ the various modes are:
Off no assistance
Eco the motor contributes an additional 50%
Tour the motor contributes an additional 110%
Sport the motor contributes an additional 170%
Turbo the motor contributes an additional 275%
The drive can put out up to 60Nm of torque through a derailleur but is limited to 50Nm of torque through any hub gear
Any downsides I hear you ask, well, yes a couple. For better or worse the bike is damn heavy! Clocking in around 20 kg (and when your're touring you gotta haul the charger around with you adding more weight...) The other negative is that Reise & Müller bikes are eyewateringly expensive, but you get what you pay for and these bikes have a certain beauty, state‑of‑the‑art technology and that 'German' robust efficiancy you expect from their high‑end products