Di2 internal battery on a bike with no internal cables

I have a trek 2100zr, I am going to install a dura ace 9070 groupset with an internal battery, I would like ideas on how to rout the cables. I am not afraid to drill holes, I know a guy who works at a machine shop who can drill any holes in the frame, though I would prefer not to. I have already voided the warranty, so I have no worry’s about the warranty. I would like to mount the battery inside the bike. my goal is just to get a nice clean look. and I am not interested in an external battery or jc40 junction. my frame has no internal cable routing, I need to find a the bast way to get the cables from my junction a to my junction b. I can 3d print parts as needed for this build. one of the ways I was thinking about is to remove the bottom bracket(I’d prefer not to though) rout the di2 cable with my rear break then down my drive side seat stay and put the junction on the wheels side of my chain stay. the battery I dont know if the cattery cable can go through the hole at the end of chain stay. the other option that I thought of was to drill 2 holes , one in the top tube and one in the bb.

I’m not saying I know anything specific about your exact frame, so I’m speaking in generalities. I’ve never drilled holes in a frame and don’t recommend doing so. Basically ignore what I’m about to tell you. LOL.

  1. Probably you best bet is to mount the Di2 battery in the seatpost still.
  2. For the cleanest routing, I’m guessing you’ll have to go thru the bottom bracket. There might not be a ton of clearance for wires as it’s just an AL shell I would believe.
  3. guessing your best best for getting 3 cables (shifters, fd, rd) outside is thru the drain hole on the bottom of the BB shell. <-- this is where you’d have to drill out a bit and see if there’s enough clearance for the BB to install.
  4. shove the junction B box up the seatpost or down tube.
  5. Junction A at the handlebars or for cleaner look the bar end Junction A.
  6. I believe there are specific di2 wire kits for externally routing your cables on the bottom of your chainstay/down tube.

Again - I don’t recommend this, but that’s what I got for you. GL.

thanks, that was helpful, this is simalar to what I’ve been hearing at roadcc

I added Di2 to my 2013 Madone 3.1 - low end carbon bike - agree with advice above…

I put the battery in my seat tube with a wire out a slightly enlarged bottom bracket drain hole - only about 1-2mm wider was enough to get the plug through. The wire is narrower, so it can still drain easily. I didn’t have to remove the press fit BB to do this which was nice! And you can fish it ahead of time using a rigid wire to make sure the path is clear from there to the seatpost.

Not sure why you are opposed to junction B under BB - there is one type that just replaces a bracket already there for shift cables and you’ll never see it. Has been very durable and reliable - never touched it after install.

I tried going through my chain stay to the RD - it looks like it could be hollow but it wasn’t for me, and I wasn’t about to drill an internal rib that could be structural. The black shimano “tape” they sell to hide the cables is super discreet - esp. on my black frame - and I have to say I’m amazed how well it’s held. It’s pre-shaped to perfectly hold the cable. 10k miles later, not a hint of peeling or trouble with it. It’s worth the ~$15 for the kit.

I also did the bar end Junction A - this requires drilling a 5-6mm hole near end of your drop to get the wire back out to the shifters - which is fine on alloy bar as there will be no real torque at that part of the bar. Everything else is concealed under bar tape, and route to downtube partially alongside brake cable.

Overall I’m glad I did it and in long run, I don’t think it would have been worth drilling open top tube, etc. Some people have success drilling out the rivets for their shift cable guides but after I encountered an obstacle in the chain stay, I didn’t want to drill those out only to find the same thing inside the downtube - whenever I take out my GXP BB again, maybe I’d do it if I could verify a clear path, but probably won’t bother.

thanks for your advice, I’ll try that