Fridge/freezers are typically divided into three groups based on size: compact, medium and large. A compact fridge (typically 12-25) is small enough to fit between the front seats. You don’t need a complicated dual battery system and simply plug it into the 12 V cigarette lighter socket.
The disadvantage of such a fridge is that it probably doesn’t freeze. It is only suitable for water, cooldrinks and fruit. Expect to pay around R1 500. Medium-sized fridge/freezers (25-65 litres ) often have two compartments: one for frozen food and a second that merely keeps stuff cool. Some of them work really well, but because the two compartments flow together, it can get tricky to regulate the temperatures in the two sections individually.
These fridge/freezers cost an average of R7 000. A large fridge/freezer (65 litres and more) has compartments that are physically separated with separate temperature controls. Here you can use one compartment to keep braai meat frozen and the other for veggies, eggs and drinks that shouldn’t be frozen. Large fridge/freezers definitely need a dual-battery system. Expect to pay at least R10 000 for these machines.