The power house of 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 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)500 times rechargeable life Optional battery mount adapter is available if standard mount is not compatible Reliable & secure water resistant terminals Easily removable for charging Battery weight is 68 grams