Thanks for the suggestions. My goal is maximum efficiency, and I’m trying to take advantage of the middle of the big battery to get it.
Seems to me a simple DPDT relay would be essentially 100% efficient. Buck converters (inductive or capacitive) are usually only 90% efficient.
I’d also like the small battery to see *exactly* half the big battery voltage. When I balance the big battery (by using higher than normal charge voltage) the small battery would also get balanced.
My mosfets have Rdson of only 1mOhm and my switching frequency is very low (I don’t need energy storage like a buck converter), so I think my circuit would be extremely efficient...
My only concern is if the half-bridges get slightly out of sync my load could see 48 or 0V instead of 24...
Thanks -Bob