LN I can't reply to your PM you have it turned off
if your 450ah battery
bank is dropping from 12.5v to 10.1v (with load off) with 45ah taken out then the batteries are beyond shot. and time for new ones.
I would confirm they are fully charged and your battery monitor
and voltage gauges are all correct and the above info is right (ah draw and voltage) before buying
I would also look into why they lasted so short. if they are gel batteries you are probably over charging
them. the outback needs to be set for gel voltages and so does your alternator
. if you have a internal regulator
on the alternator
you can't do this and require an external reg and modified alternator.
gel batteries are picky and I would replace with flooded or agm