I will tell you what I did, sounds a little bit different as you are doing it with FD and I did it with RD.

I have a New P3, ran Ultegra Di on the whole bike. TT Shifters are the "new" Ultegra ones, no base bar shifters, 5 port junction box, 11spd FD, Internal Battery, and **10spd** RD. Works like a champ no problems and plugged in right out of the box and it was fine.

Maybe take your 10spd FD to a local shop that has a complete 11spd Di2 bike and unplug FD that is on bike and just plug it in to yours and see what happens? That is what I did with the 10spd RD.

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-Brad Williams
Website | Twitter: @BW_Tri |Instagram: @BW_Tri | Strava | Co-Founder & Coach at: KIS Coaching
Partnered with: Zoot Sports | Precision Fuel &Hydration | ISM

Your best bet is to give me a smoking deal on your 6770 deraileurs and buy new. :)

any chance you have pictures or more information on the internal battery you installed on a new P3?

thanks

Shoved it right into the seat post. Just put bike back together today after traveling, will get a picture next time I take apart. Or if you really need it I could take it apart again.

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-Brad Williams
Website | Twitter: @BW_Tri |Instagram: @BW_Tri | Strava | Co-Founder & Coach at: KIS Coaching
Partnered with: Zoot Sports | Precision Fuel &Hydration | ISM

what battery did you use?

Round skinny one. Sorry don't know part number. About the size of a cigar if not a little slimmer.

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-Brad Williams
Website | Twitter: @BW_Tri |Instagram: @BW_Tri | Strava | Co-Founder & Coach at: KIS Coaching
Partnered with: Zoot Sports | Precision Fuel &Hydration | ISM

The cage shape on the FD will be slightly different between 6870 and 6770 but they are basically the same in terms of function.

The RD is the only part that is 10/11 speed specific.

I spoke with a shimano master technician. He stated the 6770 FD is compatible with the 6870 shifter.

I received the 6870 upgrade kit from my wife for my bday. The 6770 is going on her bike.

I just did what you are describing. Had 6770, got a deal on 6970 front and rear derailleurs and wanted to keep my exterior battery and shifters.

First thing was got a firmware update on the whole 6770 for $40 at local shop. Then I put on the 11sp carriage on my enve wheel. They use dt Swiss hubs, so they pop on and off, very easy. Then a slight re dish at a local shop.

Put on the front and rear derailleurs and they worked perfectly. Then I realized my old chain pin pusher wouldn't work, so I took the bike to a local shop and for another $40 they put the chain on and adjusted the derailleurs. Took it for maiden voyage yesterday and everything worked amazingly! Next job will be routing the battery internally.

Oh, don't fall for the 'need for 11sp chainring' bs. My old quarq with SRAM red black rings worked perfectly.

I know this post is really old, but for anyone considering doing this (as I was a couple weeks ago), Shimano updated their firmware so now you can't mix and match RDs/FDs now. So if you have a 6770 shifting system you can't just put a 6870 RD in it and have it work. As for the shifters you can have 6770 shifters with 6870 derailleurs.

What if I want to use a 6770 group (TT bar end shifters, FD, RD) and add 6870 brake lever shifters? Can I simply add them with a 5 port hub and will it work OK? I'm keeping it 10 speed.

Should not be a problem,once you connect do firmware updates.

In the past I have used 6770 road shifters on 6870 group.