Depending on type of batteries, and brand, because you really do need to go to the manufacturer of your batteries to find out proper equalization voltage, you may need to disconnect the batteries from the rest of the 12V electrical, as it can take 16.0V to do a proper equalization on many flooded lead acid batteries, which is too high a voltage for the circuit board on some Refrigerators. So you need to talk to the technical department of whoever makes your fridge too, to find out maximums safe voltage during battery charging to not fry the circuit board.
It's not as easy as it seems, so do you homework, for battery manufacturer, charger manufacturer, (can they get to 16.0V for a proper equalization charge) and elctronics in your rig, so you don't over voltage them, or have to isolate batteries from electronics to properly equalize.