The fine detail of USB technology occupies a lengthy Wikipedia page, but the salient points are that USB port output is a nominal 5V, which will charge any device supplied with a USB connector cable, and that USB power adaptors supply current as required by the charging device, generally from 500mA up, in some cases, to 2A, per port. Current – in amps – determines the rate of charging, and a battery’s capacity the time taken to charge it at a given rate. The Exposure Strada 800’s own dedicated charger supplies 1.5A, so two Strada 800 lights connected to a twin port charger capable of supplying 3A should charge in the usual time. Depending on the lights you use and the time you reach your digs, a 2A twin charger might still charge your lights by bedtime.
Cycle’s Technical Editor