PRO Di2 Internal Battery Holder for Fork Steerer

Fitting a Shimano Di2 battery has gotten easier thanks to PRO’s Internal Battery Holder. They make two versions of a mount that allows you to secure the battery inside your bike. The first version, and the one you expect, is the one that fits inside round seatposts. These are designed to work with PRO’s 27.2mm and 31.6mm diameter posts, though they should work with most other manufacturer’s round posts. The part is simple. It’s two halves of a cylinder. You put the battery inside the halves, with the cable side down, and push it in. PRO also includes a tool to pull out the battery for those few times you might need to. The second version is one that fits inside a fork’s steerer tube. Yes, the fork. Like the seatpost mount, it’s two halves of a cylinder and should fit in most round 1 1/8” steerer tubes, with the ribs crushing slightly to accommodate small diameter changes. The Di2 battery is 152mm long and 16mm in diameter, so you’ll need a steerer tube that’s 2cm longer to accommodate both the battery and the mount. you’ll also need Di2 cables, a Di2-compatible stem and top cap, and Di2-compatible handlebars (these have tiny ports for the Di2 wires.