Shimano di2 battery adapter for 27.2mm seat post

thingiverse

I swapped my Di2 battery to another bike, so I needed to transfer it to a new post. Luckily, my 3D printer came to the rescue! (You can see that I damaged the battery during removal from the previous post). I designed this sleeve to fit over the Di2 battery and fit inside a 27.2mm carbon seatpost. Print this thing with flexible filament. You might need to experiment with wall thicknesses and infill percentages depending on your filament so it's squishy enough to insert inside the post. I had to print a couple of times before I was happy with the fit. My final settings were two wall thicknesses and a 10% infill with cheap Chinese TPU. It fits my post, so it may or may not fit yours. Not all posts are created equal. Print two of the sleeves. Slide one sleeve up so that it locks into the notch on the battery. Slide the second sleeve up so that it locks into the notch on the other end. Slide the battery and sleeve assembly into the seat post. This should require a fair amount of force to slide it in, as you don't want it to vibrate loose when you ride. I've ridden most of one season with this system, and there's no hint of any movement to it. Let me know if it also works with your seatpost!