The following is my how-to to fully internalize Di2 on the 2010 S3 frame.  This is not as simple as I wanted it to be and requires electronic soldering skills (there over 25 26 gauge wire connections to solder).  My original plan was to drill/dremel the frame opening so that it can use the Di2 internal wire kit as is but I decided against doing anything to the frame and concentrate on customizing the Di2 wiring instead - $200 wire kit < $4500 frame.  Sucks that all the opens are just a hair too small for the Di2 connectors.  Here is the Pre-Di2 pic:

 

Notice the shift cables routing around the stem and into the top tube. This actually was a big pain as I was rubbing against them when out of the saddle.

After about 6hrs and 30 solder connections I fired it up and everything worked 100%.  Not sure if it was skill or luck but I was quite skeptical that everything would work right off the bat.  Most of the time was spent checking and double/triple checking everything to ensure that my plan would work.  Overall, it was an interesting project but not sure if it was worth the time and effort spent?  If I was to do it again I may just internalize the battery.  I have done many hours of Internet searching, reading and thinking on the best implementation so here is my recipe on fully internalizing Di2 on a 2010 S3:  Here is the completed ride:

No more cables routed around the stem.  Instead, the main control wire is split and routed down the existing ICS-3 holes and tied to the rear brake cable.  The grommets are from the Di2 internal wire kit and made a nice cover for the openings.

 

The Di2 status device is mounted on the right side of the stem.

Here is the RD entering the back of the chainstay.

   

Thanks Cervelo for the super large opening and bottom bracket area as I was able to tuck everyhing back into the frame without much effort even after wrapping everything in shrink tubing.

Things needed and where to get:

1. Di2 components (obviously)a.        Shifters (ST-7970)b.        Front wire kit (SM-EW79)c.        RD/FD (RD-7970/FD-7970)d.        Internal short wire kit (EW-7973-1) I got components from ebay seller melfren and internal wire kit from amazon.com
2. TEnergy 7.4 1200mAH lipo stick battery and TEnergy universal smart charger for lipo Got these from Amazon – Battery superstore 
3. Model Power 2 conductor wire 26AWG (#2302) Got from local model train store
4. Any 18-20 AWG power wire Used old power supply line for PC harddrives
5. Heat shrink tubing for 24AWG, 20AWG and 3AWG wire Got from local model train store as home depot/lowes does not have anything this small
6. Mini Tamya male plugThere should be a plug that comes with the charger.  If not, any model RC store
7. Soft styrofoam padding (type used in insulation) Home Depot
8. Electronic solder gun and rosin core solder Radioshack
9. (Optional) Third hand tool with magnifying glass.  My eyes are not what they used to be? Radioshack

Technically speaking, you can use any 26AWG and 20AWG wire you like.  It can even be built using single strands from Radioshack (24AWG only).  I went with the Model Power stuff because it is a cleaner install.  Also, do not skimp on the heat shrink tubing as this not only insulates but adds strength to the connections.  I double up on the shrink tubing.  Used 24AWG for each lead and 3AWG for the entire connection

Integrating battery in seat tube (appetizers)

I determine putting battery inside the seat tube is simpler than inside the seat post then using the seat post like a cap.  The reason is that the battery will slide out (due to gravity) and into the seat tube over time.  The entire battery holder extends about 2” from the top of the seat tube so that I can remove it easily after the seat post is removed.

1.  Cut and shape the foam so that it securely fits inside the seat tube of the frame and stops at the water bottle cage top bolt with 2” extending from the top of the tube.
2. Measure the length of the seat post that is inserted in the frame and from the top of the foam mark that length + 2”.
3. Trim from the top to the mark so that it fits into the seat post
4. Cut out a section to fit the battery and connectors starting at the top.
5. Cut a channel from the bottom of the battery section to the bottom of the foam.  This is for the wires.

Splicing wires and routing in frame (main course)

1. Remove existing derailleur wire guide at bottom bracket and ICS3 liners.
2. Cut power wire that connects the Di2 battery holder to the main Di2 junction device
3. Splice in the Mini Tamya connector and 20AWG wire (long enough to be unplug at top of seat tube)
4. Route power wires from top of seat to hole at bottom bracket
5. Solder to power leads from Di2 bracket
6. Cut all Di2 FD, RD and down tube wires about 2” from main junction connection side
7. Measure and splice in wiring to FD and RD cable from FD and RD points to bottom bracket hole
8. Route FD and RD cables thru frame and recombine the main junction connectors
9. Measure and cut the 26 gauge wire the length of the down tube.  Make 3 sections
10. Take 1 section and split the wire so there are 2 individual wires
11. Take 1 of the individual wires and combine with other wire to make one 3 lead wire.
12. Cut the wire from internal wire kit labeled “Junction 1” about 2” from the end that connects to the front status box.  You are essentially replacing the original Di2 downtube wire with 2 separate wires (a 3 lead and a 2 lead wires) routing them thru the ICS3 holes.  Splice 3 leads to 1 wire and splice the other 2 leads to the other wire.  Make sure to keep track of the leads.
13. Route each wire thru frame using existing ICS3 FD/RD holes and recombine it with the connector at the bottom

Making connections (dessert)

1.  Connect up system and test
2. Put battery and wires into foam channel and insert into seat tube until it stops and about 2” extends from top
3. Replace seat post
4. Push connectors and wires into hole and secure junction to bottom bracket.  Thanks Cervelo for once for having a large hole at the bottom bracket.

Here are some pics during the project:

Here is the main Di2 connection block with the battery connection cut that is mounted to the bottom bracket.  Unlike other pictures that I have seen there are only 2 leads here (which makes sense).

Here is the RD wire cut.  Notice that there are 4 leads here.  Both the FD and RD have 4 leads and the main wire has 5 leads.

Here is a full test prior to install.

This is an excellent project and thanks for the write up. Please can you be a little more specific as to what charger you're using. I've done a search but not come up with a suitable result. Thanks!

Nice work!!!! Questions: - Any problems once ridden (humidity ...)? - You substituted the battery. How long does your battery last?

Long term not sure but from reading other di2 posts it's long term even in cross and mtb has been proven. As for my personal experience since it's been installed I put on about 2k miles and the charge is still registering at 100%. I have not removed the battery yet

Thanks for the write-up.  That first picture at the top is deceiving.  I thought your saddle to bar drop was a foot.  Then I saw the second one and realized it's just the camera and the angle.

Great write up. I am considering putting the battery in the seat tube. How is yours working? Would you still use the same one? I currently have my battery hanging upside down under the bottom bracket and it collects a lot of grit and becomes difficult to remove.

 Tim

@stanseven 

The picture is a bit misleading but I do have a larger drop than most.  However, the seatpost is at different heights from pre and post pics.  Since the pre was taken I switched to a mid-sole cleat position on the bike (google "midsole cleat friel") so I had to lower my seatpost to maintain proper knee angles.

@colorchange

I am no battery or electrical expert and this was recommended on another site as an alternative battery matching voltage of the orginal.  That said the stick battery does have a higher mAh than the orginal (560 vs 1200), a 20c discharge rate and its a lithium polymer so just from those specsI would expect it to last much longer (from usage and self-life) than the orginal.  Batterywise its a bit heavier but since there is no casing, holder and mount there are considerable weight savings using this alt power source.  In fact, I am thinking about using a much smaller battery (< 300 mAh) for race-day but at that point your spliting hairs?

I have said that if I was to do this again not sure if the ends justify the means.  Hte bike does look awsome from a cable management perspective but all that soldering sure took a lot of meticulous work.  I do think that internalizing the battery is a super easy thing to do and adds great value (weight, looks, maintenance) to the system.  The jury is still out on the alt battery but I have had no problems to date and 2000 miles - still saying full charged at this point.  

 

how is this going now? and what battery would you choose to reduce weight? something around the 600??? how heavy is the 1200?

Still working like a champ and after all this time it's still showing full charge. The battery weight is trivial...it's already so freaking light compared to the original because there is not case and extra connecting components. Using a smaller battery is splitting hairs. But to your point I am not sure of the exact weight

awesome!!!!!!! do you have any pictures of the way you kept the wires away from the BB axle? I am looking to do this with a zipp vuma quad and it has a pretty thick axle!!! other question is what difference would be made by using the internal wiring kit from shimano? I still would have to splice the wires,,,, just your thoughts?

williamsf1:

awesome!!!!!!! do you have any pictures of the way you kept the wires away from the BB axle? I am looking to do this with a zipp vuma quad and it has a pretty thick axle!!! other question is what difference would be made by using the internal wiring kit from shimano? I still would have to splice the wires,,,, just your thoughts?

The S3 has an internal sleeve around the BB so the wires never come into contact with the crank axle.  Initially, I was concerned that this inner sleeve seals the frame tubes. from interconnecting.  I have never personally seen the external wire kit so I cannot comment on the difference.  What I can tell by looking at diagrams and docs the internal one is 1) longer in length, 2) has zip ties attached to the main wire, 3) comes with grommets, 4) comes with an inner sleeve for BB.

http://techdocs.shimano.com/media/techdocs/content/cycle/EV/bikecomponents/EW/EV-EW-7975-2902A_v1_m56577569830682463.pdf

When I ordered my Di2 I was able to select internal or external so from a price perspective there was no difference.  Either way, yes the cables need to be splice so I guess it does not really matter.  But the grommets came in handle.

 

 

thanks!!!! and is it possible to not have that ugly junction box? any chance you can post some hi res photos to flickr or similar? I would love to see more detail of your build!!! thanks!!!!!!

williamsf1:

thanks!!!! and is it possible to not have that ugly junction box? any chance you can post some hi res photos to flickr or similar? I would love to see more detail of your build!!! thanks!!!!!!

You must be referring to the one on the handle bar as the other one is under the BB so you will never see it unless the bike is flips...and if that happens there are other things to worry about.  I fell once moving slow on another bike and more concerned about the frame vs. myself - sad but true.  I have seen a post on the Internet that a company put it in a hollow stem...other than that I have not thought about it much.

I can post to flickr later.

But everytime you recharge the battery you have to remove seatpost?

scico:

But everytime you recharge the battery you have to remove seatpost?

Yes that is true and it is a con of the system.  Right now, I am still determining how lone the battery will last.  To date it is still showing full charge and its been about 2 months and 1.5k miles.  This means that at a minimum we are looking at 4 months so far.  I am hoping to get that least 6 months so 2 times a year which is my normal interval to strip and clean the bike that includes removal of seatpost.  Considering that its just 1 single bolt and about 5 seconds to loosen its worth it to me...since I now never need to replace cables (normally once a year for me).