Shimano XTR Di2 installing the battery in the fork steerer

To describe how I moved the battery SM-BTR2 to the fork steerer so that I could get rid of the SM-BTC1 (external battery case) I went to workshop and bench assembled the parts I used, you have to imagine them being stuffed (gently) down the steerer tube from the top. In hind sight I should have taken photos as I did the install.

There are the parts required:

1. SM-BTR2 Battery
2. Pro Di2 Internal Battery holder
3. ESI Racer silicon grip (but any foam that will not absorb water should work)
4. Correct length e-tube to reach from inside bottom of steerer to Digital display.

Although I think I used a 350mm e-tube rather than the 250mm one I put in the photo as a demo.

Everytime one is connecting or disconnecting an e-tube you are using the correct tool TL-EW02 (I think one came with the rear derailleur):

The magic

Work flow went like this (assuming a squeaky clean bike):

1. Remove front wheel, put to one side where you won’t trip over it.
2. Remove stem/ bar assembly/ zap strap it to fork leg so it does not rub on anything.
3. Use long wooden dowel and soft hammer to tap through star nut from top to bottom of steerer. Once it gets to where the taper opens it pops out the bottom easily enough. Put to one side after checking petals as you will re-use it later.
4. Slide battery inside section of ESI Racer grip.
5. Insert Battery SM-BTR2 into Pro Di2 Internal holder with e-tube terminal at opposite end (ie it will be at the bottom of the steerer tube):

6. Gently insert battery, ESI grip silicon spacer and Pro Di2 battery holder into steerer tube.
7. Slide long thin zip tie through the holes in the Pro Di2 battery holder.
8. Using wooden dowl and soft hammer gently tap assemby into steerer tube so that it is deep enough to allow proper insertion of star nut.
9. Thread zip tie around lower teeth of star nut with the tail end poking through the upper teeth of the star nut (so you can grip it with pliers later).
10. Thread star nut tool into star nut, line it up and tap it in with soft hammer.
11. When star nut seated properly, remove seating tool, grip tail of zip tie with needle nose pliers and pull slack through and trim with side cutters.

Imagine this all inside the steerer tube:

So now there is the battery assembly “hanging” from a zip tie under the star nut, held in place by friction with the Pro Di2 battery holder and padded with a ring of ESI silicon grip. The battery terminal is visible from the under side of the crown (wear a head torch for this bit).

12. Draw a circle on another piece of flattened ESI grip with a sharpie, using the inside of the ESI grip as a guide. Trim it with a pair of tin snips/ shears so one has a circular silicon plug.

It can just be seen here:

13. Drill a 1.5mm hole in the circular plug and then squeezed the e-tube head through that hole, relying on the silicon to stretch a bit and then be a tight fit on the e-tube.

14. Use the e-tube tool to insert the e-tube head into the battery terminal.

15. Apply a small amount of gorilla glue around the edge of the circular silicon plug and pushed it gently into the inside of the silicon ring formed by the grip protuding past the end of the battery inside the steerer tube.

16. Finally then insert the other end of the e-tube into the Digital display (using the e-tube tool).

I actually threaded the e-tube through some heat shrink tube (along with the e-tube to the rear derailleur/ down tube) then shrunk the tube to hold it all neat and together.

17. Replace stem and stem/ steerer cap, torque as required, check all the bolts you have played with to be extra safe, and re-install front wheel.

Go test ride…..works…..go to fridge and get a cold beer, tell yourself you are a Di2 install legend!