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.