Hi Smiles,
Despite the brand, the Engel Smart Battery Box S2 could be worth considering for your Waeco.
Nathan at our Melbourne store did a vid covering off its features if you wanted to watch it:
https://youtu.be/3MkngnRiNekPrice and specs on the Battery Box:
https://www.tentworld.com.au/buy-sale/engel-smart-battery-box-series-2We sell Ritar batteries, we have found them to be good value & well priced.
https://www.tentworld.com.au/buy-sale/ritar-agm-battery-12v-120ahThe Engel Smart Battery Box was designed around people not wanting to go to auto elecs, or if they're changing vehicles often, or in some cases are fleet vehicles where modifications are not allowed.
It has DC-DC built in with cig tip for charging.
Mind you, like all cig tips they can wobble loose and are not the best rough road socket.
To connect your fridge to the Engel Smart Battery Box, you can go into one of the cig outlets. But if you're doing off road, or just want to eliminate one connection that could be better I'd grab an Anderson to Female Merit plug adapter so you can connect using your Merit plug on your Waeco cable.
Sadly, I've not been able to source my own yet (I have asked Narva to make them!).
In the meantime, these guys on eBay do make them:
https://www.ebay.com.au/itm/Anderson-Plug-to-1-x-Merit-Socket-2-x-Female-Cig-Socket-Car-Fridge-Engel/111114854072?hash=item19def61eb8:g:dH0AAMXQLoZR2i-gIt is worth considering bringing better cabling into your car, and ditching the cig plug on your Engel Smart Battery Box. A cool cable for that is the Dometic 12RU-U2 kit. It just needs to be brought through the firewall to battery, and has smart ignition sensing so will cut off supply when cars off (no need to find ignition!!!).
https://www.tentworld.com.au/buy-sale/dometic-waeco-fridge-wiring-kitI hope this helps.