BT-DN300

Brand: Shimano

Internal battery of semi-wireless 12-speed Di2, introduced with Dura-Ace R9250. Shimano quotes 500 mAh at 7.4 V for 52 g and three E-Tube SD300 ports, feeding the derailleurs that stayed wired. There is no dedicated charger: charging goes through the rear derailleur port of the R9250, R8150, R7150 or RX825 with the EW-EC300 cable, in about 1.5 hours from a USB mains adapter.