Shimano D-Fly Master Unit issue

Hi all,
I’ve transferred a D-Fly unit across from a sold bike. I don’t know if I have killed the D-Fly unit or if I am just not able to bring it back into service.
I plug it into the new bike (Ultegra D6800 system). Connecting it to the E-tube app I can register the unit “S5EU101”. I press to connect it. It goes halfway around the circle to connect. Then I get the error message “An unknown master unit is connected. Check the master unit”.
I’ve tried to check and change things around but without any success. Have I got a fried D-fly or is there a way to check the master unit?
Thanks Mike

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When you say ‘Ultegra D6800’, do you mean 6870 Di2?

The “Master Unit” is the battery. What battery / battery mount do you have installed on that bike?

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Yes it is a R6870 on the rear derailleur. The battery is internal to the saddle post. Normal di2 functions well. It’s a 2016 Giant Defy bike.

There are two different seatpost batteries (that are 10-speed/11-speed compatible).

If this is the battery that came with the bike, it is probably the SM-BTR2. The SM-BTR2 is not compatible with the EW-WU111/EW-WU101.
The SM-BTR2 is compatible with the older d-fly, SM-EWW01 (ANT only).

The newer BT-DN110 seatpost battery is compatible with the EW-WU111/101 D-Fly.

(BT-DN300 is 12-speed only)
((6870, without the ‘R’ :wink: ))


Thanks Terry,
That must be it. I can’t read the battery master with the bike. It is the original battery. I have two D-Fly units and they are both the EW-WU101 units. I’ll pack it away and wait for the day that I upgrade the battery.