Rather then using an inverter you might consider a 12 volt cpap. The 12 outlet is easy to add. For 30 amp 12 volt service run 10 AWG wire from the DC distribution panel to where ever you want the 12 volt outlet. I added two in the bedroom for fans when we dry camp.
2016 Axis 24.1 E-450 6 spd tranny
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You should really install your inverter very close to your battery and then run a 120v extension cord to your appliance. 30 amp DC really needs an 8 ga or heavier wire to avoid too much voltage drop and I have never seen a 12v lighter plug that will handle it. You need to look for a trolling motor plug and socket to handle the current and heavy wire. If you need to run more than 6 feet of DC wiring you should go to 6 ga or more.