Shimano Di 2 Internal Fit Battery 7.4V 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 Reliable & secure water resistant E-tube terminals connection Charging is done via stem junction or handlebar display Battery weight is 50 grams BT-DN110