Charging 12-speed Di2 is simpler than earlier generations—no dedicated charger unit to buy, no battery to remove from the frame. The EW-EC300 is just a cable with a USB-A plug on one end and a proprietary magnetic connector on the other. Plug the USB end into any power source that delivers 5V at 1A or more, snap the magnetic end onto the charging port on your rear derailleur, and the internal battery starts charging. A standard USB wall adapter, laptop port, or portable power bank all work fine.

The magnetic connection on the derailleur end makes attachment foolproof. The connector finds its orientation automatically and clicks into place on the small charging port located on the rear derailleur body. There's no fumbling with pins or worrying about inserting it wrong. When charging completes, the derailleur's LED indicator shows the status. The 1500mm cable length gives you enough reach to charge the bike on a stand or leaning against a wall without the power source needing to sit directly under the drivetrain.

Beyond the drivetrain battery, the EW-EC300 also charges Shimano's power meter cranksets. The Dura-Ace FC-R9200-P and Ultegra FC-R8100-P cranks have their own internal batteries for the power measurement electronics, and those batteries use the same magnetic charging interface. If you're running a Di2 drivetrain with a Shimano power meter, this single cable handles both charging needs—just move it between the derailleur and crank arm as needed.... Read More