Yellow box means it’s a RailKing, not a Premier, locomotive, as does the 30- stock number. (Premier is a 20- stock number.)
Since this is a PS2 locomotive and the battery isn’t as critical in its function, you can forget about the battery being the issue. A new battery won’t solve anything.
It seems like Your boards on the locomotive are shot. Not surprising for PS2 with the 5-volt boards. Sorry, but your choices are to convert it to a simple conventional locomotive or upgrade to PS3.