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In Remembrance
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Discussion Starter · #1 ·
I have 2 - 80 W solar panels, a charge controller and an inverter due to arrive next week. I think I have most of the planning under control except for the wire sizing.

From the PV (4.56 Amps) to the charge controller - 15' one way = 2 -#12 stranded. (?)

Charge controller to Battery 3' - 2 #10 stranded (?)

Battery bank - 2 - 6V 225 AH Golf Cart batteries in series = 12 Volt
may increase later, or may move one of the PV panels to the barn and start another system.

Battery to 1200 watt inverter 3' or less (no idea)

Where should I place fuses? Size?

Ideas, comments and suggestions appreciated.
 

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#10 wire should be fine for everything even though it may be a bit large for some of the smaller load. #10 wire according to the electrical code is good for 30amps and #12 wire is good for #20amps. As far as fusing... size the fuses to match the load. Is a load is 7 amps then use a fuse as close to 7 amps as practical
 

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Offgridkindaguy
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I'd use #8 between the panels and the charge controller. 2-80 watt panels is 13.4 amps.
 

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In Remembrance
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Discussion Starter · #4 ·
I'd use #8 between the panels and the charge controller. 2-80 watt panels is 13.4 amps.
Hmmm? Maybe I'm doing it wrong but I thought that 2 80W panels in parallel = Voltage same ~17V @ 160W would be roughly 9.5 amps. If #12 is rated at 20A shouldn't that be enough?

Taken from panel specs:
Voltage (peak) 17.10
Current (peak) 4.68

Just trying to understand....
 

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When your saying #12 \ 20A your talking about a 120vac circuit.

DC is a different critter.
Consult a wire loss table and find that yes #8 would be correct.
If you use that #12 you could forget about using the charge controller . . . . . .there will be that much line loss . . at 12vdc.
 

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Offgridkindaguy
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This is a nice little tutorial on A.C./D.C. differences with wire loss charts for different voltages.

Just remember when using these wire loss charts, they are talking a "one way" run, assuming that the ground is easily accessible like in a car stereo set up. This is not true when figuring the right gauge wire in a solar set up. Either double your current or the distance on the chart and you'll be good to go..

This is a quick reference when figuring wattage and amps. Type in your "working" voltage (12, 24, ect.) and the wattage and you'll get the true "working" amperage.

Hope this helps..
 

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When your saying #12 \ 20A your talking about a 120vac circuit.

DC is a different critter.
Consult a wire loss table and find that yes #8 would be correct.
If you use that #12 you could forget about using the charge controller . . . . . .there will be that much line loss . . at 12vdc.

#12 wire will safely handle 20Amps reguardless of the voltage.
 

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Offgridkindaguy
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"#12 wire will safely handle 20Amps reguardless of the voltage."

You are correct BUT it depends on the distance of both conductors and the "type" of current you are dealing with. Like jim-mi said.. Low voltage D.C. is a totally different critter.

12 gauge wire @ 12 volts D.C. will carry 20 amps for 3.79 feet to stay within the 5.00% loss factor. (assuming a positive and negative lead in the circuit from the source to the load) Both leads need to be considered as distance and part of the circuit.

@ 120 V.A.C., assuming 2 leads in the circuit from the source to the load, 12 gauge wire can carry 20 amps 37.88 feet and stay within the 5.00% loss factor.

The lower the voltage, the larger the conductor needs to be to avoid losses at any distance and considerable current load.
 
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