The power house of 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 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 lifeOptional battery mount adapter is available if standard mount is not compatibleReliable and secure water resistant terminalsEasily removable for chargingBattery weight is 68 grams