I believe only one 5V pin is available on the shield form factor pins. The other is on the double wide header on the end of the board. They are both labelled.
Out of curiosity, why would you want to use two power sources for 5V? Do you need precisely 5.0V available? More current? There is some dropout after the USB. I usually get about 4.8V (guessing from memory).
Shear convenience heh. I’m running a bunch of dynamixel servos on a 14.8V pack (16V at full charge) and already have a v-reg on board for something else that brings it down to a stable 5V (7-amp switching reg). Didn’t feel like putting a 6-9V reg on there too just for the Panda.
I don’t need 2 sources for 5V, but I need to know if I’m going to break something if I’m wired into the v-reg + battery and attached to my computer for programming at the same time. (again, shear convenience; I can just pull the battery off while I’m dumping code)
Yeah I’m not saying it’s right, but I’ve powered my Panda ii with the 5v pin quite extensively. I designed a board that mates with the 40 pin connector, and it has a 5v regulator onboard so I figured why mess with a separate power supply.