Inside Di2-compatible seatposts and frames, Shimano's BT-DN110 battery handles two jobs: powering the entire shifting system and serving as the network's master unit. That second role matters because the battery contains the processing hardware that makes Synchronized Shifting possible. The onboard chip stores your shift pattern preferences and manages communication between all connected components. When you pair a wireless unit like the EW-WU101 or SC-MT800 display with your Di2 setup, the BT-DN110 is what establishes the Bluetooth connection to your phone or tablet. The E-Tube Project app then talks directly to this battery to configure shift patterns, run diagnostics, or update firmware across the entire system.

The cylindrical design measures 17mm in diameter and 160mm long, sized to slide into standard seatpost interiors or frame-specific battery mounts. Shimano includes the plastic mounting hardware, washers, and lockring needed for seatpost installation. Most Di2-ready frames and seatposts have dedicated cavities for this battery, though routing varies by manufacturer. If your frame lacks internal battery provisions, the SM-BTC1 external bracket mounts the same battery to your bottle cage bosses, keeping everything functional on older frames or custom builds.

One charge delivers roughly 1,000 to 2,000 kilometers of shifting depending on terrain and how often you use the front derailleur, which draws more current than rear shifts. The SM-BCR2 charger connects through your junction box, whether that's a bar-end unit or stem-mounted, so you never need to remove the battery for routine charging. A full charge takes about 90 minutes from a USB adapter supplying at least 1 amp, or around 3 hours from a standard laptop USB port. When battery level drops critically low, the system enters a preservation mode where the rear derailleur continues working while the front derailleur locks out to save your remaining shifts for getting home.... Read More