As I’ve described elsewhere on the tandem forum, I converted our tandem with a Cytronex C1 and have also added one to a solo bike. The battery/controller, which fits into a special “bottle cage,” is interchangeable, so I only had to buy part of a kit to accommodate both bikes. Fitting the kit from unpacking takes about 30 minutes. Weighs only 3.6kg or about 8lb in real money!