Waeco CoolPower RAPS 44AH Battery Pack

I would use the fridge during the day and have it plugged into a vehicle charging source ie, dedicated Anderson plug. Perhaps a ciggy plug if you must, but they are not realy good for long term/frequent connections because they work loose and get hot and burn the plug. Hence no fridge working.
Although the RAPS has a few plugs the thing costs $299.
With a similar battery in a box and anderson plugs for connection to car and fridge you should be able to halve that cost. Maybe even have a handle on it too.
An Aldi DEEP cycle battery is 40 AH and available on their specials each year. The battery cost is $99. For less than the $200 difference you could buy the necessary gear to suit your needs.
In that a Jaycar digital voltmeter $15, to monitor the voltage level and switch to switch it off when not required is also affordable in that $200 spare.
A couple of andersons and some suitable cable will be required too.

Don't recall seeing the current draw for your fridge, but 44Ah is rather thin for that task.

Couple of things with that Chris.

The Waeco raps 44 has the batteries inbuilt and all comes ready to go.
That is ok, but all batteries will eventually cark it, a lot depends on maintenance / charging, not letting AGMs run down too low, say max 50% SOC.

If you bought a battery box, you could choose your own battery as mentioned (aldi or other), and when it eventually dies you can buy another.

Not sure if the Waeco unit battery(ies) are replaceable, but if they are I bet they'll be $$$ more than equivalent other after market.

Someone mentioned specs for fridge running.
5c isn't terribly low, most seem to run their fridges on 1, 0 or like myself -1, keeps beer just off freezing in the middle, while cryo packed perishables live great around the outside near the plates.
I'd expect most modern fridges would run at those temps using about 1.5 amp/hr avg give or take.

The Waeco would do it ok overnight, but you'd need to drive next day to recharge, if 12v charger is anything like my old Arkpak charger (thing it was 6 amps), you do need to do a decent 5 or 6 hours driving to top off again, OR get a 150w of so solar panel to top it off during he day if camped up and not driving.

If driving, a battery box (and maybe the Waeco box) can be wired up to charge from the alternator, much faster, usually an hour, two max and mine's back to 100% SOC . . . or at least as much as it can be, but SOC and how much batteries really recharge on trips is another matter).

Yes the Waeco box you linked to would suffice, you'd probably have to wired up to charge from the vehicle alternator anyway, or get solar.
You can likely set up your own slightly higher amp/hr AGM battery in a battery box for quite a bit less.

We have the Primus 44ah power pack and used it with our Waeco CFX 40 and haven't had any problems running the fridge for a day or so. The reason we chose the Primus over the Waeco Raps was that it seemed to have a few more features. We also use a flexible solar panel to keep the power pack charged.

Why not put a solenoid under the bonnet ,wire the main battery up and run decent twin wires to rear with Anderson plug and use battery box.That way refrigerator is isolated at night it would be cheaper and use what size battery you like.Very simple to do.

Hi Chris i have one recently used on last day of camping trip day to power waeco 40l cf set at 3c day temp 27c o'nite 10c battery 80% when checked when got home. I also have 100ah batteries and love the portability of the much lighter power pack.

If you want to measure the SoC accurately you need to isolate the battery and let it sit for 3 hours.

And if you go the RAPS route, starting properly charged, you'll have around 22 amps before hitting 50% SoC which is the desirable minimum. Say you're in camp for 15 hours, you can draw 1.5 amps per hour.

That's not accounting for losses, which will be minimal with good wiring and the fridge close to the battery pack.

But for that application I would go for a 100 Ah battery to provide some wiggle room (like another day in camp or power for a light or device charging).

Also budget for a smart 240v charger for battery maintenance. A 10 amp unit for a 100 amp battery eg.

Chris
I used a Waeco RAPS 36 with a 50litre Waeco set much the same as you describe except that I had a RAPS12R-U2 plug connected with heavy cable directly to my car battery instead of the car ciggy plug. This unit can be set to deliver power all the time or with ignition only (I used the latter setting). That means the Waeco battery is only connected to the car battery when ignition is on. So the Waeco battery plugged into that and the fridge plugged into the battery. Worked really well for overnight stops or anything up to about 18-20 hours.
So - yes - a 44AHr battery should be fine.
Kevin