No you where not getting lucky before
The battery Monitor loses tract of your charge and gives a false reading .
( My out back resets the % of charge every time I get a full charge ) so it could stay at full charge but the battery’s will lose a little every day .
no the battery bank can be added to w
ith in the first year but there are consequences
2 battery’s may not be enough over all power .
But as is 4 battery will die from under charging
( Just a small helpfull thing )
Your battery are different they where made at different times and one set was in service longer Then the other
I would make sure the batters are in series
With one newer battery and one older battery then parallel them together older battery’s need more charging .
The bank will be more equal .
The lower ah battery has thicker plats or maybe just more room for liquid ?
But generally they will last longer it’s a trade off between more power and longer life .?
Do you have a on board genarator ?
In a pinch tractor supply has a heavy duty farm and ranch battery charger I think I payed 120 bucks 4 years ago .
You can charge 6 volt or 12 volt with it
You can charge one bank of 2 series’s connected battery’s with them wired into the the system .
This is close to what i have but is a smart charger mine just puts out constant power .