Electric bikes are an intriguing transportation alternative, but four- and five-figure price tags are just too much for many people to spend on a limited-utility, low-range electric vehicle. That price looks even steeper for those that already have a perfectly functional pedal bicycle sitting at home. Japanese-Swiss company Sunstar hopes to make e-bikes a little cheaper and more versatile with its modular Virtus electric drive that transforms a regular bike into an e-bike, then detaches in minutes, effectively giving you two bikes in one.

The Virtus joins the growing list of aftermarket e-bike add-ons that includes the likes of Rubbee and the Velospeeder. As a mid-mounted e-drive fitted around the bottom bracket, the Virtus is a more cleanly integrated power option that's similar to e-drives used on permanently electric bikes.

Sunstar says that the Virtus is designed to fit any conventional bicycle frame, transforming a standard bike into an electric bike with up to 15.5 mph (25 km/h) of e-assist speed potential. Knowing what we do about the sheer breadth of the bicycle industry, we're sure there are a few "conventional" frames on which the Virtus will fit about as well as a square peg through a round hole. However, the potential versatility of the system is an attractive quality; instead of having to buy an all-new, multi-thousand-dollar electric bike, you can transform the bike you already own into a seamless, mid-motored e-bike.

The two main components of the Virtus are its 250-watt, 55-Nm motor and a multi-sensor controller that controls motor output and tracks torque, cadence, crank angle and speed. The multi-sensor unit can be used without the motor, providing performance-tracking on a standard pedal bicycle. The Virtus hardware also connects wirelessly to a smartphone to support performance-tracking and control features.

Sunstar has developed three battery options; an 11 Ah, 400 Wh rear rack-mounted battery; an 11Ah, 400 Wh battery mounted atop the down tube; and a dual battery system with the 400 Wh down tube battery plus an 8 Ah, 300 Wh battery secured to the underside of the down tube. The system includes an LCD computer for adjusting between four modes, tracking battery level, and getting read-outs of speed, mileage and other metrics.

The Virtus hardware is designed to be removed from one bike within minutes and then installed on another bike. So if you have a quiver of different bikes – maybe a mountain bike, race bike and in-town commuter – you automatically have a low-hassle quiver of e-bikes, assuming the Virtus works smoothly with the different designs.

Sunstar is showing a Virtus prototype at this week's Eurobike show. Outside of listing a weight of 7 lb (3.2 kg), it has not announced further specs or pricing information. It sounds as though the system will be available both over the counter and integrated into full bikes.

Hopefully, we'll have more on this one as it makes its way toward production.

Source: Sunstar