Pianotuna, it doesn't sound like the OP was planning on using inverter - I understood that he only wanted very few and very low-current 12V devices. A small 100W-150W inverter for a few minutes of electric shaver and/or a few hours of cell phone charging should still fit into that scenario, if he makes sure to turn the inverter off when not in use.
Yes, some propane detectors draw 0.3A, this is 8 Ah a day - unacceptable high draw for a minimalist setup. If this is the case, he should get a better unit. There are dual propane/CO detectors that draw 0.1A, i.e. 2.4 AH a day.
He has a travel trailer, not a MH, and I don't see how parasitic draws - not including fridge which I consider a useful load, not a parasite - can exceed 10 AH even with the worst detectors. Radio on standby or separate radio clock is another "bad guy" that he should keep an eye on - this one can draw 4-5 AH a day, and if this is the case, he should turn the radio off for the night completely, just pull the fuse - or again, replace it with AA battery device.
