I ultimately decided against DC barrel connectors for the power feed to the OZroll roller shutter controller, as they are
2) supposedly rated at only 3 Amps
3) have only two conductors, making remote up/down button signalling difficult in future
I opted for 4 pin microphone connectors. They are rated at 10 Amps per pin, are nice and shiny (improving wife acceptance factor), and have a screw collar for positive and secure engagement. I went with white sheathed 6 core cable. One pair carrying 12V DC, one pair carrying Ground, and the remaining pair kept spare for later used in remote signalling of roller shutter up/down commands.
Here is a front and rear view of the connector mounted in a blank wall plate
It turns out that they have 0.2 inch pin spacing, making a breakout board easy with veroboard and terminal blocks:
And here's the breakout board soldered into position:
Labelling is always good, in case you don't remember what you did in 5 years time. See also the jumbo Clipsal wallplate to cover the SLA battery compartment:
And here's the hole in the wall with custom sheet metal glued into position, drilled and tapped for screws to accept the clipsal wall plate (I couldn't find suitable mounting brackets from the electrical supplier).
The drilled out tongue depressors were invaluable in maintaining alignment of the sheet metal while being glued and clamped.
In summary, the nominal 12V, 3.3AHr, SLA batteries I have installed to replace the OZroll NiMH batteries last a few weeks before needing charging again. This charging will be automated in due course. The batteries have very low demands placed on them and should last many years, unlike the OZroll NiMH battery packs, all of which among my six roller shutter controllers have long since died.