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 &40;as a wireless system would require 4 batteries: one for the RD one for the FD & one for each shift lever&41; 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 &40;as this is the main power drain&41; 500 times rechargeable life Battery is to be mounted with seatpost or frame manufactures hardware normally inside the seatpost or seat tube Reliable & secure water resistant E-tube terminals connection Charging is done via SM-EW90 junction A Battery weight is 50 grams