If you're running Shimano Di2 with an internal seatpost battery, you've got two options: trust the OEM mount that came with the bike, or replace it with something that actually holds the battery still over rough roads. The Ritchey Di2 Rubber Battery Seatpost Mount handles the second job. It's a simple elastomeric sleeve that wraps the BT-DN110 or BT-DN300 battery and friction-fits inside the seatpost, keeping the battery from rattling around and protecting the cells from abrasion against the post wall.

Ritchey offers this mount in two diameter ranges to cover the common seatpost sizes. One version fits posts with an inside diameter up to 27.2mm, which covers most road and gravel bikes running traditional round posts. The other fits posts larger than 27.2mm, typically the 30.9mm and 31.6mm range you'll see on mountain bikes and some gravel frames. Both versions cradle the same Shimano Di2 batteries (BT-DN110 and BT-DN300) , so the difference is purely about how the rubber sleeve sizes to your post, not which battery it accepts.

Installation is tool-free. The rubber compresses enough to slide the battery-plus-mount assembly down into the post, then expands to lock against the inner wall. No adhesive, no screws, no internal expander hardware to tighten. If you need to pull the battery for a firmware update or to swap to a different bike, you tug it back out the top of the post. The flexible material also absorbs the vibration that would otherwise transfer from the post into the battery housing — useful on gravel and chip-seal, where a loose internal battery can clunk audibly inside the post.... Read More