Calfee Design is now offering an elegant solution for the Shimano Dura-Ace and Ultegra Di2 electronic shifting systems: a proprietary internal battery and wiring system, capable of working with any bicycle.

The innovation starts with a custom battery system housed inside the seatpost. An aluminum sleeve is machined and bonded to the inside of the seatpost and serves to anchor a removable battery. A circlip acts as a stop and retains the battery inside the aluminum sleeve. Remove the circlip and the battery is freed. The battery can be fit in seatposts of any size as Calfee fabricates composite shims to take up any space between the aluminum sleeve that retains the battery and the inner wall of a seatpost. Inserting this battery into aero posts is also possible. In some cases, we will use foam instead of our aluminum housing to secure the battery in the post. Importantly, you need only remove your seatpost from your frame to charge your battery. You needn’t remove the battery itself from inside the seatpost; we offer this feature as a thoughtful design detail. In the near future, we expect to introduce a modified harness that will allow you to charge your Calfee Di2 Internal Battery without removing the seatpost. This accessory will likely be mounted in the handlebar area and, through a USB port, should be capable of powering any number of electronic accessories.

The Calfee solution is 8% lighter and significantly longer lasting than Shimano’s product. In fact, field testing reveals that our battery will last between 2500 and 10,000 miles, depending on temperature and how often the front derailleur is made to move the chain between rings. At a minimum, that is 2 to 3 times longer-lasting than the Shimano battery. Conveniently, Shimano’s inline battery life indicator displays our battery’s status. You may charge our battery as often as you like; you needn’t discharge it completely before returning it to the charger that we provide. You will not do damage to our battery either way. Our battery can be completely depleted and recharged hundreds of times before its ability to hold a complete charge begins to slowly diminish.

The Calfee Di2 Internal Battery and Wiring System eliminates the need for cable ties, adhesives and external mounts, improving the bike's form and enhancing its aerodynamic function. To achieve fully internal routing for the electronic shift cables, Calfee makes the necessary modifications to the wiring harness, battery, seat post and frame.

Please note: the version we are selling here includes the Calfee Di2 battery, as well as an Evo carbon 27.2 seatpost (with the Calfee aluminum battery sleeve already built-in), the Evo carbon saddle rail wedges, and Calfee-specific 7.4V Li-Ion battery wall charger.

If you would rather use your own seatpost, we can arrange for that. Please be in touch and we'll make the arrangements with Calfee.