In the Alba Combi you can set two types of batteries, the ones associated with the engine PGN often referred as “alternator” in within the PGN or as a full battery with its own NMEA2000 PGN.
In the latter case the battery can use any of the 12 voltage inputs on the Alba Combi and you can measure from 0 to 32V, depending on the configuration you can use a temperature sensor for the battery and a shunt to measure current, all that information will come together in the PGN and will be shown on the display as a whole battery.
The calibration table in this case will be a simple two points calibration, 0,0 and 32,32 so that you can use the full voltage range.
If you are measuring more than one battery one aspect to have in mind is that all ground have to be common.
The PGN will have three fields, voltage, temperature and current, you don’t need to use all of them.
The instance will have to be selected so that will not have conflicts with other batteries in the NMEA2000 bus and will be dependant on what your display will need to detect them.
