The Shimano Di2 Internal Mount Battery is the power house of Shimano Di2 is a long-life 7.4V Li-Ion battery that is both compact and reliable, taking shifting effort away from you. Excellent sealing and reliability have been proven through repeated field tests in various riding conditions, including extreme temperatures, rain, mud, and cobble stone roads. Using a hard wired battery system which is both light weight and accurate compared to current wireless technology (as a wireless system would require 4 batteries: one for the RD, one for the FD, and one for each shift levers Shimano Di2 Internal Mount Battery Features One charge can give between 1000 and 2000 kilometre range depending on conditions and front mech operation (as this is the main power drain) 500 times rechargeable life 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 and secure water resistant E-tube terminals connection Charging is done via stem junction or handlebar display Battery weight is 50 grams