Di2 Charging with 2 Junction-A boxes?

fastguy2014

Hello all, thanks in advance for any help here. I am contemplating hiding my Shimano junction-A box that would normally rubber band to the underside of the stem, inside the stem cavity. Drawback, charging port and battery indicator are no longer accessible. Upside, no wires.

If one was to connect a second auxiliary junction-A box to the rear derailleur e-tube, could you use that connection to the system to charge your internal battery, or connect to the e-tube software?

Thanks in advance!

Bar Shaker

Even if it was possible, why on earth would you?

fastguy2014

Simple, to hide the wiring and junction box. As I mentioned...

Bar Shaker

It's only a hunch, but you may struggle to find someone that has done this before.

ellotreacle

If it helps Ive seen it done on a website, as I was looking in to doing it my self. I have looked for it, but unable to find it but will keep looking.
Im sure the guy used a SM-JC41 junction box in his stem, and came off of the junction box by the bottom bracket going up through the top of his seat post and mounting the recharging external port under his seat. (although not possible if you are using a seat post battery) but from the jist of his wiring as long as all of the wires are connected using the junction boxes the set up should in theory work.

I gave up on the idea as it was far too much work just to hide the external box.

Hope you have better luck.

trailflow

(although not possible if you are using a seat post battery)

Its not ideal but you can put the internal battery at the bottom of the seat tube if you wrap it in some kind of padding. When i tried Di2 with the internal battery, it would drop out of the seatpost and end up like this anyway. It didn't rattle and i didn't notice it.

OP if it works,how do you plan to run the etube down tube wire past or around/through the steerer ?

Also if you want to go full stealth,wouldn't you need to drill holes in your handlebars to run the shifter cables to the stem ?

It would of been better if Shimano initially designed it so the junction-A box was incorporated into one of the Di2 shifters and then two wires run out from it. 1 wire to the other shifter (running across under the bar and stem) and 1 wire into the frame. That would also remove the need for an extra wire. Have the button,recharge port and led light indicator underneath the hood. That would have looked much cleaner.

Pokerface

On a couple of my bikes I don't use the 3 or 5-port junction box because it's too big. I use the old A-junction box instead - as it's easier to hide. (This was particularly an issue on my TT bike where I needed to hide as much of the cabling and junction boxes as possible.

So when I need to charge the battery (internal seatpost one), I simply plug the 3-port junction box into the rear mech cable. Charge overnight - and job's done.

964cup

Hiding it in this way will also mean that you lose the ability to trim the derailleurs or recover from crash protection mode without plugging a second junction-A into the network somewhere (and you'd need an extra EW-SD50 to connect the temporary junction to whichever component you'd disconnected so that all components were visible for trim). Colin's suggestion of using the older style of A-junction (from 6770) is a good one if you can live with that being visible, and (bigger if) it's still supported in the latest 6870 firmware - note that recent revisions have apparently suppressed the ability to mix and match 6870 and 6770 components. You'd still have to charge by plugging in another junction A - although there's a hack to put a regular e-tube connector onto the charger instead of the unique 2-pin connector that only fits the new-style junction A, if you're happy to cut up your charger cable.

Bar Shaker

The downsides of this seem huge, compared to an aero advantage that you could achieve by having a shave.

Can't you just wrap the junction box and wires to the underside of the stem with some black insulation tape?

964cup

Sugru is your friend. I used it to fit the di2 box to the stem of my "Commutant". Looks like this:


Would be easy to fair it in for a more aero effect.