Didn't know this. You can charge Di2 through any port:
"Hacking the SM-BCR2 to have a standard Di2 cable connector: If your 3-port or 5-port junction is inaccessible for charging, there is an alternative hack method to connect it to the system through a standard Di2 port. With basic soldering skills you can hack the BCR2 to be used with any setup. Buy any length EW-SD50 wire, cut off one end. Cut the wire on the output side of the BCR2. Splice the two wires together, so that the output wire of the BCR2 is now a standard Di2 connector. The charger has an inner (white) and outer (shield) wire; connect the inner white wire to the SD50 red wire; connect the charger outer shield wire to the SD50 black wire. You will then be able to plug the BCR2 into any Di2 port. Or use a SM-JC40 junction B and another length of EW-SD50 wire and go through the RD (by using the SM-JC40 to connect the rear derailleur, new output wire of the EW-SD50, and the wire that ordinarily connect the rest of the system to the rear derailleur.) Thanks to @Di2diy for the info." http://carltonbale.com/shimano-di2-everything-you-need-to-know/#chargers_pc_usb
Not yet. I keep being tempted though as I'm sure it could be reconfigured into a smaller and more waterproof unit for ultracycling. I doubt there's much to it internally.
Didn't know this. You can charge Di2 through any port:
"Hacking the SM-BCR2 to have a standard Di2 cable connector: If your 3-port or 5-port junction is inaccessible for charging, there is an alternative hack method to connect it to the system through a standard Di2 port. With basic soldering skills you can hack the BCR2 to be used with any setup. Buy any length EW-SD50 wire, cut off one end. Cut the wire on the output side of the BCR2. Splice the two wires together, so that the output wire of the BCR2 is now a standard Di2 connector. The charger has an inner (white) and outer (shield) wire; connect the inner white wire to the SD50 red wire; connect the charger outer shield wire to the SD50 black wire. You will then be able to plug the BCR2 into any Di2 port. Or use a SM-JC40 junction B and another length of EW-SD50 wire and go through the RD (by using the SM-JC40 to connect the rear derailleur, new output wire of the EW-SD50, and the wire that ordinarily connect the rest of the system to the rear derailleur.) Thanks to @Di2diy for the info."
http://carltonbale.com/shimano-di2-everything-you-need-to-know/#chargers_pc_usb
Anyone pulled apart a Di2 BCR2 charger?