You may already be familiar with the good impression made by the highly versatile 24in wheeled folder, the Airnimal Joey. Airnimal has now coupled the Joey with an electric assist system (the BionX EPS) to produce that rarest of things; a quality, practical folding electric bike.
The excellent folding and riding features of the Joey are well-noted. The BionX system itself has been around for a number of years and has a proven track record, especially in its home country of Canada.
As electric bike systems go it's relatively discreet, consisting of an unusually large-diametered but thin hub motor, nicely-shaped Ni-MH battery and a small handlebar mounted LCD console which allows you to control the various power settings. It works on the Pedelec power assist principal (i.e. no throttle), so that power kicks in once you are up to about 5kph and takes you up to a max of 25kph, where power cuts out. The Joey, being a sporty bike that demands to be ridden, means you now have a rather unusual creature - an electric bike that is still very 'bike-like' to ride but gives you a very firm, virtually silent and constant assist up the hills (especially in the top two power settings - but more of this later).
The bike rode well without power (though as with any electric steed you wouldn't want to run out of juice many miles from home in difficult terrain) and the battery charged on or off the bike in around five hours. Extra LCD functions include battery level meter, speedometer, odometer, trip distance and time. Electrification hasn't interfered with the excellent fold in the slightest (the battery can be removed or locked onto the machine while in transit).
There's more to the BionX than a nice power assist system though - as far as I know it's unique in being the only regenerative kit on the market - that is, one that uses the motor to feed power back into the battery while descending or braking. This regeneration is controlled by four of the eight power settings you access via the console (A to H), A giving you a real hill-climbing boost and H providing enough braking from the motor so that you don't have to touch the brakes on all but the steepest of descents.
How much regeneration this provides in practice is difficult to say without riding the bike over many, many months and in differing conditions; I consistently managed to get over 30km on a single battery charge in moderately hilly country. As with cars and petrol consumption, how, where and in what conditions you drive/ ride can all make a significant difference to the power you consume. Without a doubt though, overall the BionX is a very efficient system.
My only niggles were that the console buttons are very difficult to control with gloves on and the lower power and regeneration settings seemed to have little effect and could arguably be dispensed with. If you have concerns about the weight a lighter Li Ion battery is said to be in the pipeline for UK release later in 2007.