Older Di2 systems running external batteries can gain E-Tube connectivity and Synchronized Shifting capability with the right hardware upgrade. The BM-DN100 Short Battery Mount isn't just a bracket for holding an SM-BTR1 battery in place. It contains the updated electronics that enable wireless communication with the E-Tube Project app and support Synchro Shift functionality when paired with a compatible wireless unit like the EW-WU101 or EW-WU111.

The short version fits frames where space is limited or where the longer mount would interfere with other components. It attaches to standard water bottle cage bosses using the included M4 x 10mm bolts and offsets the battery position to leave room for a cage above it. Some riders mount it on the downtube, others underneath the chainstay depending on frame geometry and wire routing preferences. The design accommodates both internal and external wire paths, so you're not locked into one routing approach.

One E-Tube port on the mount connects to your system wiring, linking the battery to the junction box and the rest of your Di2 components. Through this connection and a wireless unit, you can update firmware, check battery status, and configure shift settings from a smartphone or compatible cycling computer without plugging anything into the bike. For riders who want to adjust shift timing or set up Synchronized Shifting modes on the trail or at the start line, this wireless access makes a real difference.... Read More