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Old 01-07-2013, 05:22 PM   #1
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1966 24' Tradewind
Fall River , Massachusetts
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Wire gauge from Battery to Converter

Hello all,

I am still chipping away at restoring my trailer and I am currently wiring the converter. All is going pretty well but I have a simple question. What gauge wire should I use to go from the batteries to the terminals of the converter? I am planning on putting the batteries within 6 feet of the converter which is a Progressive Dynamics 4045.

I ask because I purchased some nice 4 AWG wire and it seems a little big. I barely fits into the battery terminals of the converter and even at that, some of the wire fibers are not in contact. I have heard that 4 AWG is a good choice and to always lean on the size of a larger gauge but am I missing something here? Thank you all.

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Old 01-07-2013, 05:45 PM   #2
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You are not pushing a high amp motor. A 10 gauge wire will do fine for a simple Airstream install.

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Old 01-07-2013, 05:55 PM   #3
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Thank you. Could it be salvaged to wire a couple of solar panels the battery?
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Old 01-07-2013, 05:57 PM   #4
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converter wire size

While I do not know the size of wire required for your application, I do know that in general use 10AWG is rated at 30 amps. That seems a little light, in my estimation. Many times a finer stranded wire is used, such as welding cable as it is easier to work with in bending as well as increasing ampacity.
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Old 01-07-2013, 06:32 PM   #5
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Here is an ampacity chart Ampacity Charts. These charts are typically set up for a maximum run of 50 feet and the recommended wire gage would drop the voltage no more that 2%. Note: this chart is addressing alternating current, but it will work equally well with direct current (any voltage).

Since the Progressive Dynamics 4045 is rated at 45A maximum DC output, the maximum charge rate to the battery would be 45A (here's the installation manual link, but you probably already have a printed copy So the bottom line is that you would be absolutely fine with 8 gage wire.

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Old 01-07-2013, 06:33 PM   #6
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I just rewired an Argosy 20' and I used #8 for a 4 foot run. I personally would use either a #8 or #6. jmho. Everybody will have their own thoughts on this I am sure.
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Old 01-07-2013, 07:46 PM   #7
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#10 would make me a little nervous. Bigger is better.
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Old 01-07-2013, 08:01 PM   #8
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I decided to locate my batteries across the isle from the charger location/fuse block so I ran a pair of #2's under the floor. This gives be the option of locating an inverter near the charger and not have to worry about the voltage drop.

All in all, it was just as easy to go BIG as it would have been to go too small.
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Old 01-07-2013, 08:20 PM   #9
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wire size

I just rewired my 65 Caravel. I placed two six volt Trojan bats behiind the propane bottles in a diamond plate shoe box. I ran #4 welding cable to a splice where the original 12 volt battery was under the bed. I used #6 awg from the coverter to the splice. I think #10 was a little light for a 5 foot run.

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Old 01-07-2013, 08:39 PM   #10
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West Marine used to have a better page on this, but their current Wire Size Guide is good for visually showing the effect of length on wire and choices. I liked their last detailed chart of 2% voltage drop better. It pushed the recommendation up 1 size in many cases.

According to the chart, 10 gauge for 6 feet would work. That said, I usually go larger -- not quite as much as Vernon, but close.

I just installed a PD 4045 and used #4 wire for a 3 foot run. If I didn't have it handy, I would have bought #6. BTW, the #4 sounds like severe overkill for solar, but it would work.

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