quick question i forgot to ask:
In a dual battery setup, one being charged one being sourced, can the grounds be common? Can i connect the grounds of both batteries to the source input/common and do the charge/source switching with the positive input?

Seems like a no brainer but I am getting inconsistent results.

 

Can you show us a schematic? You should be able to share grounds with no problem. What kind of inconsistancies are you seeing?