Shimano BT-DN300 Di2 internal mount battery, 3-port

From Shimano:

• 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
• The use of a single small and discreet internal battery is light weight, efficient and creates a robust and reliable system
• One charge gives a 1000 kilometre range depending on conditions and front mech operation (as this is the main power drain)
• 500 times rechargeable life
• 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 SD300 E-tube terminals connection
• Charging is done via stem junction or handlebar display
• Battery weight is 50 grams