EE needed for schottky diode question

Thanks for the replies! I removed the original pictures because there were some issues with the circuit and I don’t want it to potentially mislead someone in the future.

 

Not sure why you wanted to use a Schottky diode, but your circuit should work to auctioneer the two sources just fine. I don’t think that step down transformer is going to work very well in a DC application though.

 

Agreed. Definitely going to need a DC-DC converter instead of a transformer. Maaaaybe something like this one (it was the first one I found) https://www.alliedelec.com/product/traco-power/tcl-060-112-dc/70062740/ (may not work due to voltage ranges. Need something with a lower input if you're doing 18V batteries with a 0.7V diode drop)

Only other thought is that you're going to be burning off some .7v*4A = 2.8W off of each of those diodes, so they're going to get hot.