. The power house of Shimano Di 2 is a long-life 7.4V Li-Ion battery that is both compact & reliable, taking shifting effort away from you Excellent sealing & reliability have been proven through repeated field tests in various riding conditions, including extreme temperatures, rain, mud, & cobble stone roads. Using a hard wired battery system which is both light weight & accurate compared to current wireless technology (as a wireless system would require 4 batteries: one for the RD, one for the FD, & one for each shift lever). The use of a single small & discreet internal battery is light weight, efficient & creates a robust & reliable system. One charge can give between 1000 & 2000 kilometre range depending on conditions & front mech operation (as this is the main power drain). Internal chip enables system wireless functionality of Bluetooth components Battery is to be mounted with seatpost or frame/fork manufactures hardware normally inside the seatpost or seat tube/fork steerer Features. Weight 50g 1000-2000km Range 500 recharge Life Secure water seal Buy Shimano Bike Accessories from Chain Reaction Cycles, the World's Largest Online Bike Store.