generically...
24.4v is what you should see for fully charged batteries with no load on them.
22v is about as low as you want to go for normal discharge 19v for fully discharged with about 18v as your emergency discharge level
28.8 is your nominal maximum charging voltage.
ideally there should never be more than about .3v difference between any 2 adjacent batteries.
fluid level checks in the batteries should be monthly, every 100 engine hours, or 100 hours of use depending on how you are using the batteries.
battery voltage checks should be done with the red switch isolated and with the paralleling cable disconnected (if you do it from the drivers side you can ball park the health of both banks as 24v by simply moving the earth connection from the battery -ve to the -ve cable)
emergency jumper cable or 24v clip on charging can be done from either side of the vehicle directly to the terminals (just don't grab the bridging strap that gets "interesting")

