Off Grid battery backup system charging question.

[RNeumann]

Those switches only isolate when you have one or the other bank selected. As soon as you put the switch in the 1&2 position it combines both banks. Batteries are like a bag of apples- if one is bad and the rest are good it doesn't take long before all of them are bad.
I'm assuming the Xantrex is a charger and inverter. If that's the case the only way to charge and invert the same bank is to have your switch on that bank. If you needed/wanted both banks at once or wanted to switch between banks manually you would need separate chargers for each bank. And if you wanted to use them together you would need big isolators (diodes) on each bank so the banks can't backfeed or "see" each other.
The battery type on the Xantrex changes the charge/float voltage slightly. Here is the chart from the Xantrex manual.

 

[dmccarty]

Another reason to NOT mix batteries, I might have mentioned this but it is good to repeat, is that different batteries, even of the same type and AH, can require different charging voltage. One needs to check the battery manual for proper charging voltage at a given temperature THEN see what the voltage is being used by the battery charger.

Look at the charger manual page that RNeumann posted compared to this charge voltage table segment from the Rolls AGM battery manual:



The battery requires 14.70V and 13.80V for charge and float voltage at 77 Degrees. The charger is using 14.2V and 13.2V at 80 degrees which is a pretty big difference. Partial State of Charge(PSOC) is a big killer of batteries.

One needs to match the battery's charge needs to the charger and some chargers are not adequate for the battery. Some chargers can be programmed though.

This battery OEM's website has quite a bit of battery information. Solutions : Technical Support Desk

Later,
Dan