Yeah, Charlie. I use two switches, two batteries one voltwatch. All set up in parallel so that one does not affect the other, well, unless there is a battery failure. The voltwatch is simply set up on a short leash type Y connector to one of the channels that I don't disconnect on a regular basis (rudder for instance).

But, my contention is that with one battery failure, as I had, it may work to drain the other battery, however, there is (was in my case) sufficient battery power left to finish the flight. Now, granted, I had no idea there was a failure until after I landed, so my assumption is that it worked as desired... must have, because I didn't fill a trash bag that day.

And, with any type of failure with a redundant setup, you won't have any idea.. should not have any idea, (unless some sort of telemetry is used.. yet ANOTHER point of failure.. jeech.. this could to on forever.. ) that a battery had failed until landing.

So, it's up to the pilot as to how he/she wants to set things up. As for me, I really prefer the simple solution for dual battery.. two batts.. two switches, one voltwatch. Chances of such a catastrophic failure during flight as both failing at the same time are... remote??? is that the right word? doesn't seem to give enough 0's in the count.

CGr.