Help to plan a Di2 build?

The cable junction ew JC 130 is usually used in place of the cables in the handlebar. So rather than running an individual cable from each shifter to the junction box you use that instead. So no need for that and cables for routing in the bars. Having done a few builds I'm not sure it's any neater either really. If your running the Bluetooth module you can need an extra cable, generally use a short one and run cable from shifter and leave it in bar end hidden away. Another option if your running the internal bar end junction box is to use the Bluetooth module as a cable connector too, joins the y cable in the bars to the down tube cable that joins the smaller internal junction box. I've seen this hidden in bars and stems, handy way of lengthening a cable.

Get a small bit of foam padding too and wrap it around the smaller internal junction box, stops it rattling. You can get small plastic clips, look like cable ties that clip onto the internal frame cabling too and stop it bouncing and moving as you cycle, keeps rattling noise down, https://www.tradeinn.com/bikeinn/en/shimano-ew-sd50i-wire-holders/135997388/p?utm_source=google_products&utm_medium=merchant&id_producte=2686023&country=ie&gad_source=1&gclid=CjwKCAiAnL-sBhBnEiwAJRGiguoC1OVAnLnfA0A0AdtfHDbnHrL5z8j022buyJpOzHzNrwiqZqB51RoCU40QAvD_BwE&gclsrc=aw.ds

For the battery some frames will have specific mount that wedges it into the seat tube but you can buy a sleeve that fits around it and wedges it in, https://www.tradeinn.com/bikeinn/en/deda-di2-for-27.2-mm/138042974/p?utm_source=google_products&utm_medium=merchant&id_producte=12860434&country=ie&gad_source=1&gclid=CjwKCAiAnL-sBhBnEiwAJRGigrjyd7fqaJjocvavutXCdovy8jnm0Mvxwazj0nUMEnRP-mMkPW_OuRoCtfQQAvD_BwE&gclsrc=aw.ds

I've probably just added more confusion with all of that!!

Is this for 11 speed or 12 speed rim/hydraulic? bettershifting, lama and rides of japan should have all the info needed.

re battery mount - you can get after market mounts/shims or use the one that comes with the battery - needs circlip pliers. your seatpost might also be di2 ready, so you might'nt need anything.

aside - I've a 12 speed di2 ultegra group (less wires - i think rd is the "brains") that I'll be installing myself in the next few days - just waiting for a few tools to arrive. never done anything like this before so I'll be watching your thread.

https://bettershifting.com/building-a-di2-bike-what-parts-do-you-need/