A few things come to mind. Ever see a battery explode? I have. It aint pretty. Keep connecting a battery charger when leads are live and you too will be a member in an exclusive club.
Please dont take it the wrong way, i honestly have your safety in mind.
Block it up (safely) and pop off your neutral start switch, see if its leaking. If not,heat gun and warm it up a little to get it back on, a zip-tie will help keep it snug.
Starter connection, cable and mounting bolts need to be clean.
Remove ground cable and clean block surface.
Ammeter as you suspect, can be bypassed.
Bad fuse links or improperly repaired ones can do this as well.
All free and not to difficult.