Thanks to all who replied: For TS-50+AT which draws 22Amps full load.
Summary follows:
-almost impossible to tell
-4 hrs with TS440+laptop
-12 hrs with same rig at 50W PSK
-offer to loan several EPS 22 AH batteries
-bring voltmeter and stop/recharge when batt voltage drops to 11
volts.
We'll find out in two weeks....
Bob