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 youExcellent sealing and reliability have been proven through repeated field tests in various riding conditions, including extreme temperatures, rain, mud, and cobble stone roadsUsing 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 lever)The use of a single small and discreet internal battery is light weight, efficient and creates a robust and reliable systemOne 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 lifeBattery is to be mounted with seatpost or frame manufactures hardware normally inside the seatpost or seat tubeReliable and secure water resistant E-tube terminals connectionCharging is done via SM-EW90 junction ABattery weight is 50 grams