Not sure which refrigerator you have, but most of the new ones are three way, meaning they will run on propane, 12 volts or 120 volts. You can run it on 120 volts while underway, if you have an inverter that powers it, or you can run it on 12 volts. Either way your vehicle alternator while underway, will keep your batteries charged, replacing what the refrigerator uses. Mine, for instance, is powered by an inverter, so I leave it running on 120 volts while underway. If I park for any period of time, with no shore power, I switch it to LP.
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