Steve I ran my Waeco 35 on a 55ah second battery on the Cape trip, and found it really struggled in the heat of the September Cape. I was charging it off my rooftop mounted solar panel but it would often drop below the Waeco cutoff voltage before morning. I suspect it was due to heat build up inside the KJ at night. I have seen a number of vehicles that leave the rear door open all night to avoid this heat load but obviously its a security issue in some places. At Seisia I just plugged the fridge into the camp kitchen AC and then it was fine. What I am suggesting is that 22ah might be too small for that 40l fridge/freezer , you don't want to have the voltage drop below about 12.4v over-night for long term life of the battery - even if deep cycle.