We installed one of the smart controllers when we built our new freezer. I actually thought it worked fairly well for the first couple of months. The unit senses batt voltage, and when it sees a voltage above resting voltage, say 12.6 or so (from memory), it assumes you are
charging, and takes advantage of this by lowering the box temp a few degrees. Basically your food becomes a thermal
battery.
But then I installed our
lithium house
battery bank. Since the resting voltage, say 13v or so, is above the threshold for the “smart” controller, it essentially always thinks you’re
charging, and drops the box temp accordingly. So you just have to use it as a normal (but expensive) thermostat
Bottom line, it’s a complete waste if you plan to use w
lithium batts.