OK, I think there may be confusion, so let me clarify my post. If you use two "Y"s and two batteries to the RX, each battery plugged into a different "Y", then that would be redundant. If both batteries are plugged into one "Y" and then that "Y" has one connection to the RX, it isn't redundant. Seriously, why waste money on two batteries and two switches, only to make one power connection to the RX. Batteries can fail shorted, seen it before. It will suck down a pack really fast, like faster than a typical flight. Closed circuit failures are rare, but they can and do happen. The more likely failure is a open... like pins breaking contact, hopefully not in the single "Y" into the RX.