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One of my clients wants to add a refrigerator to his mobile office (sailboat) that runs off a 12v battery bank (x2 225ah deep cycle AGM) and add x2 100w solar panels and a 400w wind generator to offset power usage. The refrigerator would be the only unit continuously drawing power. Other units and fixtures that would draw continuous power such as radar, navigation (iPad charging), navigation lights, and interior lights would need to be supported by the battery bank and solar/wind charging during long offshore passages that my client will be partaking in.

The mini fridge my client wants installed and supported is a 115v 60hz 15amp standard dorm fridge.

I have experience in proper wiring protocol and HBYC standards but am seeking guidance on the best size battery bank and solar/wind arrangement that will power a small mini fridge off grid via an inverter. Any suggestions would be appreciated!

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    My rule of thumb is that a refrigerator takes about 1kwh per day, i.e. an average consumption of 42 watts. I like to rule-of-thumb 8x the battery capacity for the daily draw, to assure that a 3-4 day run of bad weather won't flatten the lead-acid enough to damage it (they dislike being dipped more than 40% from top). – Harper - Reinstate Monica Oct 15 '19 at 3:02
  • 15 amps is crazy high, are you sure about that? i would also get a better fridge than a dorm-room special, those tend to skimp on insulation, and that's what matters most, unless you need to freeze fish or open the door 50 times a day... – dandavis Oct 16 '19 at 16:48
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15 amps at 120 volts, as @dandavis sates, is only a momentary starting current. If it really did draw that much, it would need at least 150 amperes at 12 volts, completely draining the batteries in three hours (and probably destroying them from the heavy current flow).

The client, or you, need to find what the actual total energy drain is under the conditions of use (e.g. in a warm boat), measured with a watt-hour meter, and compare that with the storage and generation capacity.

Another issue with using landlubber refrigeration is the mounting of its compressors and pipes, which is not designed to take the pounding of water travel, and with likelihood of corrosion. A much better choice would be a marine refrigerator, or perhaps one designed for an RV. Look for one that specifies average current draw at a stated ambient temperature, or ask to be able to return it if it drains the system.

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  • Not only would a marine refrigerator work better from a mechanical perspective, but you don't need to convert from DC to AC, with the efficiency problems that causes. You can just run it off of 12V directly. – user3757614 Oct 18 '19 at 6:01

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