Ha, guess what I was doing this morning? Fitting the new di2 battery that arrived this morning from Wiggle into the seat post of my bike. Then setup Synchro Shift and tested it out. All seems to work fine, just a few glitches customizing the gear changes and controlling from the Garmin 1000, which I guess they'll fix in firmware updates.
Only needs the new battery (Shimano BT-DN110) but if you want to program from a smart phone you need a bluetooth/ANT+ wireless unit (EW-WU111 or EW-WU101).
I already had a EWW01 (ANT+ only) and I'm happy to hook up to an old laptop occasionally so no need to spend the extra for the bluetooth.
Just needed the new battery for the extra brains to do the Synchro Shift. Also needed the new firmware released this week for the FD-9070 front Derailleur and RD-6870-GS rear. Also a new firmware update for the Garmin 1000 to show the shift mode and supposedly to allow it to be changed from the Garmin (but that bit doesn't work at the moment).
The key to getting it working is that to change the mode from manual, you have to double click (fast) the little button on the EW90-A junction box (the little box by your stem where you plug in the charger). Each time you double click the little button, it rotates through manual -> semi synchro -> full synchro.
If you still want to control when the front is changed, the semi mode just reverses the rear 1, 2 or 3 gears (2 is default) to compensate, something I tended to do manually.
Otherwise the full mode changes the front for you as you go across the cassette, and at the same time reverse the rear to select the next gear ratio in sequence.
You can customize this to suit, but there is a little bug stopping me from changing the drop off the big ring to start earlier than the second biggest cog on the gear, which is a shame. At the moment I've customized it to reduce the number of changes of the front slightly, but avoid big-big, and only use the 11-13T with the big ring, You can still change the front manually if you want to.
Testing it out in the garage it is amazingly seemless. I'll try it out on Monday, when the weather looks nice enough for another lunch time ride. I know it's lazy but the idea of having 14 or 15 straight gears appeals!
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Geoff