Siletzspey
Shedd, OR
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Joined: 01/24/2018
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Depending on the calculator or table you use, distance is measured as one-way (as a crow flies) or two-way (round trip). If your battery and alternator are 25' apart, that would be 25' one-way or 50' two-way (25' POS + 25' NEG). The ever popular BlueSea voltage drop table is TWO-WAY based.
As for voltage drop, the 3% and 10% rules apply to most device types, but not necessarily to DC-to-DC converters which are designed boost voltage, aka counter voltage drop.
Sterling has a video where they compare straight alternator-to-battery wiring where the wire has to be "huge" to counter voltage drop, but then with a DC-to-DC converter, the wire can be much smaller and cheaper and still get the job done. For the alternator to DC-to-DC wire, see the manufacturers length to AWG recommendations rather than needlessly oversizing/overspending on AWG based on a 3% or 10% voltage drop rule. At least for Sterling, they support down to 11.0VDC, or roughly a 23% voltage drop off at 14.4VDC alternator. To counter voltage drop on the output side, the DC-to-DC will have to pull a few more amps, and Sterling specs the 60A output could require up to 80A of input from the alternator. I don't recommend pushing the 20%+ limit however.
* This post was
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edited 01/30/23 02:55pm by Siletzspey *
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theoldwizard1
SE MI
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Joined: 09/07/2010
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I second the use of a DC-DC charger ! You can use the "stock" wiring (including fuse) from the 7 pin trailer connector.
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pianotuna
Regina, SK, Canada
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Joined: 12/18/2004
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One possible solution is a dc to DC charger.
But likely an inverter is a better choice. It can be MSW and about 400 watts.
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.
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