Battery saver

Get a better connector for the fridge for starters A ciggy socket is the worst thing to use to hook up a fridge to.
A merit plug or an Anderson plug would be far better.
Yes it would be a good idea to have whats called a fridge switch which cuts out when you stop.
You are confusing terminology A voltage controller sets the voltage you use.
A fridge switch ( low voltage Cutout switch) controls when you do or dont use it.

I've used a Cig Socket for 15 years on the Engel 40L the male end of the plug has a thermal fuze incorporated in it so all is good. I do have a piece of electrical tape wrapped around it for safe keeping. No problems at all. My 2001 model Engel does not have a low voltage cutout that I am aware of but i understand you can buy an attachment for that purpose. I check with a Multi meter and dont let the battery discharge below 50% SOC

Jeff

Shouldn't need anything else between the fridge and the power supply the fridge should have a built in low voltage cut off switch.

I have been using standard cig plug on my fridge for 12 yrs no problem just needs to be a firm fit some sockets are too loose and the plug can work it's way out or lose contact easily. I am though changing it to an Anderson plug soon because it will be living it's days out in my canopy till it stops working.

It is a very sound practice to have a low voltage cutout in the circuit between any battery supply and a high current draining device, such as a fridge.

Waeco fridges usually have a built-in cutout device but Engels do not.
Engels are a very good fridge and will keep running if sufficient voltage is present, down to the point where a battery can be drained too low and may be permanently damaged.

Low voltage cutouts will remove power when the source drops below a nominated level, usually about 11.6 volts. This represents about 1/3 capacity remaining in the battery.

Low voltage devices can be bought for as little as $40 or so and is a sound investment to protect a $350 AGM battery, or even more so, that one starter battery that some people risk using on its own.

As for "cigarette" sockets, some are good and some are bad as far as good connectivity is concerned, but all should be rated at 10A or more and would be capable of carrying the current.
The main thing to look for with plugs and sockets is that they provide a positive type of locking to guard against vibration.

I have standardised all my 12 volt "low voltage" equipment to use the Merrit/Narva style of plug with the red collar, which allows a better connection to the "cigarette" style socket. Even better is the Merrit style connection provided when the red collar is removed and the socket is a Merrit type, rather than the bigger, cheaper cigarette style socket.

For any 12 volt circuit higher than 10A, the 50A Anderson connector is the go, or even in rare cases, a 125A Anderson connector. Obviously for these circuits, suitable heavy duty twin core cabling is required, with both positive and negative cores connected direct to the battery source.