One 50Mv 500A shunt, two ammeters?

Analog needle for looking at 3" meter from a 15' distance without searching for my glasses. When needle is really tilted to the left it means the 3-1/2 digit LED ammeter should be consulted to switch to 13.4 volt float when amperage is less than point nine. Yes there are meters with inch and a half characters. Yes they cost more than 200 dollars. Yes I am using a 6-hour wind-up timer. And no this is not a converter. It is a battery charger with adjustable setpoints. The Borg, at last is being assembled. So one shunt and two meters is going to be attempted. If accuracy takes a dump in goes the second shunt.