[BrianG]

First of all, the MM will need the latest firmware that allows programming via the throttle cable.

If you have a MM with a BEC, I would temporarily re-insert the red wire into the throttle cable. You won't need a battery this way.

If you don't want to do this, depending on how you have your BEC hooked up may still require a seperate power source for the card, AND use a battery to power the MM.