Stop by Home Depot/Lowes and just get the right thing. The ones with hard wires are standard home detectors. The only difference maybe the plug and every one I have bought comes with a plug that matches the new detector so you can change out the old plug if necessary. I'm pretty sure the heat and cold in a stored RV has a detrimental effect on detectors that, for the most part, expect to live in a climate controlled space. Myself, I don't mind having to replace them sooner than in a house (detectors should always be replace every 10 years) just to be safe.