Shimano dura aceultegra di2 btr1 battery the power house of shimano di2 is a long life 74v 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 features using a hard wired battery system which is both light weight and accurate compared to current wireless technology as a wireless syst