PRO Fork Steerer Di2 battery holder
The PRO Fork Steerer Battery holder, or PRO GAP CAP Di2 as it is officially called, allows you to put your Di2 battery in the fork steerer.
It is a short expander with an integrated battery holder and it fits 1 1/8" steerer tubes.
Note: The minimum fork steerer length is 180mm. If yours is shorter than this, the battery won't fit. I have written an Installation Guide showing you how to install the battery holder.
Why would you ever do that, you ask?
Well.. not all bicycles have a seatpost capable of holding a Di2 battery. Think Canyon's VCLS seatposts, dropper posts, or full-suspension mountain bikes. This expander is a pretty good solution to that problem, especially when used together with PRO stems (like the PRO Vibe for example).
There are two versions of this battery holder, so make sure you get the right one:
- PRHS0110 - the standard version
- PRHS0111 - for use with the Tharsis Di2 stem only
There are a couple of other options if you cannot place your battery in the seatpost. The external-mount-for-internal-battery SM-BTC1 is one, but it's a bit chunky. Another option would be to put the battery in the downtube (if you can), or to use an external battery with the external battery holder.