Originally Posted by danarello

Update #2: the diagnosis was that the charging port was faulty on the RD. That's why it wouldn't charge when I connected the Charging cord to the charging port. What follows is the professional diagnosis: Item/Labor # Price Labor Di2/AXS Firmware Update with Problem Diagnosis (Repair Not Included)
"Everything works except the rear derail charging port, which isn't tested in the error check. So everything came back normal, charged this battery off of a floor bike, and tried to charge the floor bike off of this derail, and it wouldn't. To test, I had 2 different charge cables, 3 batteries, and 2 rear derails. Every combination charges UNLESS his derail is used, then no combination works. Rear derail is otherwise functional but cannot be used for charging. Also: I can connect his rear derail to E-Tube while the charge cable is plugged in, and E-Tube will normally not allow this: so the rear derail does not know it's plugged in to the charge cable. Charged his battery to 100% using our rear derail so he can ride for now." I take the bike back to the LBS this week to get the RD replaced with a new RD under warranty. wschruba, I will also share your input with the mechanic to see what he thinks. I saved $ buying the bike online, but not without several inconvenient glitches!