Hi Sassycat; Why do you need a 12 Volt clock , why not just buy one that runs off a AA battery, will last for a couple of years off one battery and there is certain to be one that would suit your caravan, and also would save you the trouble of running the 12 Volt cable from your house battery.
I imagine Sassycat wants an external powered clock with night lighting.
Some time ago I searched for a powered clock for our Jayco van. While a battery powered one was installed it couldn't be seen in the dark. As far as I could find there are no analogue clocks with lighting, and digital ones were all clock/radio type. I ended up buying a digital one that was powered by 5 Volts - being from a USB socket. I bought a separate phone charger that accepts a USB cable and that powers the clock.
The particular clock is available in four colours LEDs - blue, green, red and white with the LED numbers about 38mm. Very bright and doubles as a night light which can be dimmed.
Although my clock is powered from a 240V outlet, a car phone charger would work just as well from a 12V source.
I like to know the time when I wake up during the night. So I have used M&F velcro to position a small travel clock under the locker over my bed. It has a push button to work an inbuilt light. It works on one of those tiny round flat batteries and lasts for years. Might solve your problem.
I suggest you have a look on Mr Google for Projection Clocks, (they project the time onto the ceiling or wall at night time,) and make it very easy to see. I just ordered one a couple of days ago for about $13-00 delivered powered by 2 AA Batteries.
We have a small clock radio but needs . 240V and not much good when Freedom Camping.
We've been using an Ascot projection clock (occasionally from Aldi) for the last six years - the clock sits on the sink surround and projects up on the roof - the clock is plug-packed into 240v - it cycles every three seconds to display time - temperature - time - etc repeatedly - nice to roll over in bed, look up and know what time it is and how cold it is !
