I've done exactly the same thing a couple times. I use #10 wire, which
minimizes line drop. On low voltage systems it does no harm to run larger
wire for that reason. I also use a breaker in place of a fuse, so when
you do have a fault you don't end up with an unknown dead circuit. The
breakers automatically reset, and they aren't expensive. Available at auto
parts stores. The #10 wire should be good for 30 amperes, so don't go
any higher than that with the breaker, or the wire won't be protected. If
you are concerned with a minimum sized wire, I'd think a #14 would do the
job. The small refrigerator we run draws roughly 6 amps. You'd want to
throttle back the breaker to only a 15 amp max if the #14 wire becomes your
choice, I would think.
Very reasonable but I would suggest at least #10, #8 would be better.
The following table gives the voltage drop for 10 feet of wire at 10
Amps. Drop is proportional to run and current so 6 Amps would give 6/10
as much drop. Frame grounds tend to be unreliable. I would use two
wires from the battery to the outlet (with the breaker in the hot line
near the battery). I would guess your run would be about 15 feet so
that would need 30 feet of wire. Therefore, for a 6 Amp load with 30
feet of wire, multiply values by 1.8.
Wire size: AWG 14 12 10 8 6
Voltage drop: .253 .159 .100 .063 .040
0.6A@30': .455 .286 .180 .113 .071
While the wire will handle 30A non-destructively, you would loose almost
1 Volt on 15x2 foot run. Some appliances might not like that.
That's half a volt loss, more if a reasonable routing needs more than 30
feet of wire. As you say, probably ok but ... Personally, I like to go
heavy on wire size and have yet to regret it. BTW, #8 wire is used for
electric stove outlet wiring and might be your cheapest source.
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