Main thing to consider is the startup draw on a diesel heater. Its typically 140-150 watts, or 10-12 amps. Not terribly high, but most 12v (cigarette-style) outlets are fused at 10amps. So, a lot of people find setups and plan to use a cigarette style 12v outlet and then its fails due to over-draw. Worst yet is it may pop the fuse and now you need to replace the fuse.
All that to say, make sure your source can handle the draw. I am using a 12v battery setup and I crimped standard ring connectors on the wires and the rings go right on the battery posts of the RV battery. My RV battery is also a home-built lithium, so the voltage stays higher for longer and I get all 100% of the battery power.
Some people have good luck with the Jackery type power centers, just remember the startup draw.