With the smallest budget in the world i have patiently been scouring ebay to try and get cheap parts for a di2 set up. I got lucky yesterday and snapped up brand new shifters (6770) for less than £50 and i also have a FD for £30. This is an external routing project as i am pretty certain that my Scott CR1 is not a di2 ready frame,my question is what else do i require? So far on my list i have RD, a 5 port junction box, another junction box sm-jc40, battery and charger (not sure of model yet?) and then various cables of various lengths to join it all up. Does my beer mat parts list calculation seem right and is there anything i should make sure i get (better battery or some hidden feature rich magic connector). Thanks.

also apologies to people who offered me bits from another di2 thread but i didnt want to cause any offence when i told you how much i could pay for stuff. Your stuff was worth far much more than i could pay.

A 3-port junction A box is sufficient, no need to have a 5 port, unless you want auxilliary shifters as I don’t think 6770s have any extra ports. Equally a 5 will be fine, but means you can broaden your search.

Otherwise that looks reasonable. Don’t under estimate all the bloody wires you need!

Should be 6 wires. 2 to join levers to under stem junction, 1 from stem to BB junction then 3 to join the BB junction to the battery, the front mech and the rear mech.

Cheers njee, i will look for a 3 port junction box, i dont need auxillary shifters. How does the BB junction box attach to the bike?

Those wires are not cheap are they? That might end up being the biggest expense. I will measure the bike up so i can get the right length.

Am i right in thinking there is only 1 version of the external battery thus no superior version?

SM-BTR1 is the only external battery, there are no upgraded versions.  The external BB junction box attaches to the underside of the bottom bracket shell, where your cable guide would usually sit.

Thanks misterp, my cable guide is stick on so has no hole for a screw, does that matter?

If you are willing to fettle a bit then you can make a cable “loom” to fit  using fewer connectors/cables by getting longer cables and splicing them together that way you only need enough ends to fit the ports you require, doing this will depend on which battery you choose.

I did external cabling on mine with my own loom but put the internal battery into the head tube; again getting creative will allow the cable to fit through the SFN and top cap or top spacer if fitted above the stem, It does depend on how long your headtube is though, shimano pro make a stem that helps with this but is expensive!

Choosing the right battery is also important IIRC as the newer batteries are smart and mean you don’t need an intelligent junction box, alternatively the xt handlebar display acts as a junction box, battery charging point and Bluetooth access point of you can find one of those cheaply.

There is also info online about making your own batteries using the broken smart battery circuit if you did want to make a smaller/custom battery from a broken one which would be cheap to source.

Looking at the specs it looks like I was wrong about the junction box not being needed with the newer battery, I didn’t use a junction box as I had the xt display unit not because of the smarter new battery.

If buying Di2 components from different people/places there is something to watch out for

Before you fit the components to the bike, connect the system up off the bike and make sure it actually works

Reason being is each component has its own firmware version

If all the components are not on the same firmware range i.e 3.1 to 3.9 then the system wont work

So if one component is on firmware version 4.1 and the rest is in the 3.1-3.19 range it wont work and you cant fix this using the charger/update lead and the e-tube software

you will need Shimano’s pce-1 diagnostic tool, this allows you to connect each individual component to Shimano’s e-tube software and update the firmware for each component

Found this out when a customer returned his Ultegra Di2 bike i built and asked me to change the groupset to Dura ace Di2 but use the existing battery, junction box, wiring etc….

I had updated the Ultegra groupset to the latest firmware before he collected the bike bike but when i fitted the Dura Ace Di2 components they were on a much older firmware and wouldn’t communicate with the rest of the system

Presume the Dura Ace components had been on the shelf for quite a while so were shipped from Shimano with much older firmware installed

Escrs – yeah i have been warned about this and i reckon its inevitable that i will have to find an lbs to update something or other.

the more i read the more i confuse myself. Am i right in thinking that my shifters (6770) are compatible with 11spd derailleurs? If so is it worth getting 11spd derailleurs just so its a bit more future proof. There seems to be a lot more ebay choice for 11spd.

Yes shifters should work with 11 speed as they are just essentially buttons, obviously you will need the 11 speed front and rear mechs (think i remember hearing that the 10 speed front mech cant be used in a 11 speed system)

Ive seen before that you can hire a pce-1 diagnostic tool on eBay for around £20

Or pick them up 2nd hand for around £100 and then re sell for the same price

I seem to be slowly getting the pieces together but one thing i cant seem to work out what to do is how i am going to mount the junction box that sits near the BB. Everything i have seen has a bolt which i assume utilises a hole for the cable guide but my bike doesnt have one and the guide is just stuck on. This is an external routing set up so can somebody enlighten me as to what options i have. I am making a big assumption that i could use good quality sticky pad/tape and even if that works loose the wires will stop it going anywhere and geing lost/broken.

SM-BTC1, bottle cage mount internal battery holder and junction box.

On a MTB, but same idea

You get bottle cage mounts for external batteries as well (but you would still need to do something about the junction box)

Bigyan – its the junction box i am having problems mounting. I have the external battery mount long version utilising the bottle cage mounts but the junction box sm-jc40 seems to fix via the cable guide bolt hole that i dont have. My cable guide is stuck on although barely these days, the cable tension seems to holding it in place.

One other question, would 350mm wires be the correct size for running from shifters to the stem mounted junction box (42cm bars)?

Just use epoxy. It’s what I did with my carbon road frame 2 years ago & it’s not budged.

Yeah, just glue it on.  350mm is the ideal for 42cm to allow the loop near the shifter, you can just about get away with 300mm if needed though.

Im not 100% convinced the 10s stuff is cross compatible with the under stem junction, or that the older 10s shifters will work the 11s mechs.  I remember having some sort of problem trying to get mine to work when I tried it.

If you still need the bottom bracket junction, I have one here for £10 posted.

Blazin saddles – yeah i will buy that junction box off you if its the external type one (i think its part no sm-jc40, pm the payment details.

i reckon i might sugru it on as 3m adhesive stuff is hideous to get off if i ever need to.

I built a cheap di2 groupset 3 years ago with parts from everywhere.

Then I upgraded to discs and bought new di2 hydraulic units. No issues at all with software.

I was told you need to make sure you use same front and rear mech versions ( 6770 in my case) , the rest dont matter.

Yeah front mech and rear mech will be the same. Just need cables and rear derailleur now.

A useful guide to all things di2 :-

http://carltonbale.com/shimano-di2-everything-you-need-to-know/#chargers_pc_usb

Ok can somebody help me out because i am perplexed at what i have received. I am now in possession of a long external battery mount but i dont inderstand what the other bits are. If you look at the photo below in the link, what is the other stuff that seems to attach very loosely to the mount?

https://www.bike-discount.de/en/buy/shimano-di2-battery-mount-bm-dn100-i-long-internal-routing-532011

I seem to have hit a bit of an issue with regards to derailleurs. There is very little in the way of available 10 spd stuff which makes me think that i should look for 11spd stuff. I have a 10 spd front derailleur but no options at all for a rear so i could sell that on and begin the searcg again for 11spd derailleurs, what do people think? I am wondering if more 10 spd stuff will become available after xmas/sales when a few people upgrade, this means i have to excercise patience and have loads of second hands bits sitting in a draw for a few months without knowing if they work or not with no chance of returning.

edit: can i use a wolf link road jobby to increase a ss cage derailleur to accomodate a 32 or 34 cassette. Lots of 20% gradient hills so i need low gears.

The 10s rear mech have been as rare as for a long time now.  I’d personally ditch the front if you can find a buyer and go 11.  I’ll look for that junction later, it’s the one you need.

Thanks blazin, much appreciated. I think i have resigned myself to going 11 spd so i will throw the fd on here or on ebay..