Di2 3 & 5 port A junctin boxes

Triathlon Forum
1

So my road bike (bought used here from ST) came with a tharsis stem. Very clean and i like it. It has a 5 port inside the stem and a three port inside the fork that can pull out for charging. Its worked without issue. However, I flew with my bike and disconnected the RD and battery for packing. Upon arrival, reassembly went fine but I had no shifting. Dead. Thinking I had unplugged something in transit, i went over the whole system. Nada… Thought maybe battery died. Plugged it in. Nothing. No charging.

Well just by chance, I disconnected the 3 port used for charging. Worked like normal. Thought perhaps I broke the wire connecting the 3&5 port boxes. Nope. New wire didnt fix it. Using the 3 port in place of the 5 port works as well. Neither box is bad.

Good news is that I was able to ride. Bad news is right now I have to disassemble my bike to charge… So my question to the knowledgable people of ST - why? What happened when i disconnected and reconnected the same components used without issue? The onky thing i can guess is the frimware update I did a couple months ago and the fact I unplugged/replugged something finally had that update take place?..

I think the solution is to remove the 5 port and replace it with a 4 port (5 port doesnt fit inside the fork and i dont need those two ports anyways).

Said another way - can you use both a 3 and 5 port on the same system or can there be only one with the rest needing to be the non-charging 4 ports?

2

I don’t see why you would need both a 3 & 5 port A-junction box?

I have a 3 port A-Junction on my roadie with a 4 port B-junction box at the bb

On my tt bike I have a 5 port A-junction, then a 4 port B-junction box at bb

3

I think the solution is to remove the 5 port and replace it with a 4 port (5 port doesnt fit inside the fork and i dont need those two ports anyways).

Said another way - can you use both a 3 and 5 port on the same system or can there be only one with the rest needing to be the non-charging 4 ports?

you can have only 1 front junction (3- or 5-port–part # SM-EW90A or B) in a system. it won’t work with 2 with current firmware, at least.

the “4-port” as you call it, is SM-JC41, or an internal junction box, is a “dumb” junction/splitter. you can have as many of those as you like.

4

Youre correct - not needed but how it was when I got the bike and worked without issue until my trip.

5

Must have been allowed previously and didnt take effect until something was removed then plugged in again.

Look like I’ll be picking up a 4 port later today.

6

Was the add’l A-junction used just for charging? If so the 4 port is not going to work for you as it only has e-tube ports.

7

I’ll nix the 5 port and replace it with the 4 port, keeping the 3 port for charging as that will fit into the fork. The 4 port will be inside the stem and will use all 4 ports. The three port will only have one wire that connects to the 4 port.

There is also the standard 4 port inside the bottom bracket as well.

8

ok good plan.

9

Sorry to intrude here but I’m getting conflicting information on this very topic. I’ve got a Felt IA and the front junction box is housed beneath the brake cover which uses 2mm hex bolts. For any wrenches out there you will know that those bolts are prone to stripping (not the pole dancing kind) so I wanted to avoid removing this for charging.

I’ve been directed by many others that all they do is get an extra 3 port junction box, unplug their rear mech cable, plug it into this 3 port box and then when hooked into the system this gives me the ability to charge from that point in the system. You’re response is in direct conflict of this recommendation and leads me to believe that:

  1. You’re wrong and it doesn’t matter
  2. I’ve just purchased a junction box that will be useless on a bad recommendation
  3. Older firmware worked but newer firmware does not

Are there any Di2 experts out there who can confirm that with the latest firmware (as of March 2016) does indeed work with 2 junction box As plugged into the system?

10

From experience… I can confirm #3.

Edit: meaning my system with 2 type A boxes worked and now doesn’t.

11

I was planning on going the same route as you. I read this thread on the subject.
The way I read the post is that shifting does not work with two Junction A but perhaps charching can still work using two As.
Have you tried charging using the two As?

12

Not yet as the second one is still in the post. Once it comes in I’ll give it a go and see what happens. Worst case I have a spare as backup or for resale. When I have got this setup I’ll chime back in

13

For fun tonight, i disconnected the RD and plugged in the 5 port to charge (3port installed as normal). No dice. Pull the three port out of the system and works fine… Looks like only one type A is allowed on the system.

14

For fun tonight, i disconnected the RD and plugged in the 5 port to charge (3port installed as normal). No dice. Pull the three port out of the system and works fine… Looks like only one type A is allowed on the system.

so…basically what i said earlier?

:smiley:

15

Sorry to intrude here but I’m getting conflicting information on this very topic. I’ve got a Felt IA and the front junction box is housed beneath the brake cover which uses 2mm hex bolts. For any wrenches out there you will know that those bolts are prone to stripping (not the pole dancing kind) so I wanted to avoid removing this for charging.

I’ve been directed by many others that all they do is get an extra 3 port junction box, unplug their rear mech cable, plug it into this 3 port box and then when hooked into the system this gives me the ability to charge from that point in the system. You’re response is in direct conflict of this recommendation and leads me to believe that:

  1. You’re wrong and it doesn’t matter
  2. I’ve just purchased a junction box that will be useless on a bad recommendation
  3. Older firmware worked but newer firmware does not

Are there any Di2 experts out there who can confirm that with the latest firmware (as of March 2016) does indeed work with 2 junction box As plugged into the system?

charging MAY work–let us know. it won’t shift with current firmware, though.

16

I’ve been directed by many others that all they do is get an extra 3 port junction box, unplug their rear mech cable, plug it into this 3 port box and then when hooked into the system this gives me the ability to charge from that point in the system. You’re response is in direct conflict of this recommendation and leads me to believe that:

This process works perfectly–for charging. You just can’t shift with both still connected but that is obviously not your plan…

17

Mine wouldn’t charge with that setup.

18

Hmm conflicting information.
Did you “close” the circuit when charging? I.e. connected the RD to the system?
Don’t know if that would make a difference. Or perhaps just different firmware versions.

19

Because my setup worked with two junction A’s then didn’t, Im going to say it was the firmware update I did.

20

Joe, sorry this has happened after the firmware update. I have heard of similar things happening, unfortunately. I left that 5 port junction in the stem because I didn’t have a SM-JC41 to make the junction at the time and the system seemed to work fine with two junction A’s in place.
Besides this hiccup, I hope the bike has treated you well!