Here's my paca running off a 12v battery, without an inverter!
I've just finished soldering up a DC-DC converter. I'll bring it along to KISS2018 if you're there and want to see it. It's based on the Murata UWE-12/10-Q12PB-C... "based on".. ok it "is" the Murata UWE. There's not much more to it apart from wires, solder and a small plastic box. The tricky part is soldering the 4 pin din power plug for the paca. (Caveat, don't know if this will be enough to power a Pacarana. There's not a huge amount of power headroom.) I've just finished this so not field tested it properly yet.
(It's only taken me a year)