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Old 27-05-2017, 06:53   #1
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Correct gauge wire for solar panels

I am installing 2 345w solar panels (690w) that operate at 57v and a distance of 40' to the charge controller. I think 8g is the correct size, just wanted to double check.
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Old 27-05-2017, 07:19   #2
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Re: Correct gauge wire for solar panels

My sparkie used 6mm solar grade cabling for two 350 watt panels, but distance to the Victron is at most 7 metres.
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Old 27-05-2017, 07:41   #3
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Re: Correct gauge wire for solar panels

12AWG would be sufficient for 3pct drop at 12A current flow for a total distance of 80ft.
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Old 27-05-2017, 08:55   #4
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Re: Correct gauge wire for solar panels

12 amps.

If the distance is 40', then 80' of wire gives the complete circuit.

Blue Sea says 18GA is fine for ampacity (heat safety), but 12GA is required for 2-3% voltage drop.

edit corrected
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Old 28-05-2017, 08:29   #5
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Re: Correct gauge wire for solar panels

Most standard panels with the waterproof connectors have connection wiring systems that are 10 AWG.

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Old 28-05-2017, 08:37   #6
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Re: Correct gauge wire for solar panels

There's adequate and then there's ideal. I try to go with ideal.
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Old 28-05-2017, 09:40   #7
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Re: Correct gauge wire for solar panels

Yes keeping voltage up is a worthy goal, as is being able to add a panel without rewiring.
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Old 28-05-2017, 10:11   #8
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Re: Correct gauge wire for solar panels

It's only 12 amps I would stick with #10 AWG just to keep losses to a minimum and you have room to add more solar to the system if necessary .
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Old 28-05-2017, 14:53   #9
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Re: Correct gauge wire for solar panels

6mm tinned is the minimum I would use, and I run it in ducts.

Alternately, welding cables will give you a lower voltage drop, they can sometimes be bought tinned--but the extra expense and size over 6mm will probably save you maybe the power from ten minutes of sunshine a day--




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Old 28-05-2017, 15:00   #10
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Re: Correct gauge wire for solar panels

Not what you are asking for, but a more interesting question is voltage drop between solar controller and battery. If you use 3% rule on 12v, that'll be 0.42 Volt drop, thats quite a lot. Even your 8g is near 2% over 10ft.
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Old 28-05-2017, 16:36   #11
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Re: Correct gauge wire for solar panels

Quote:
Originally Posted by Oceanride007 View Post
Not what you are asking for, but a more interesting question is voltage drop between solar controller and battery. If you use 3% rule on 12v, that'll be 0.42 Volt drop, thats quite a lot. Even your 8g is near 2% over 10ft.


That's why the charge controller is as close as possible to the batteries.
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Old 28-05-2017, 18:20   #12
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Re: Correct gauge wire for solar panels

The question was panels to controller at 57 volts. I hope you use heavier cable from controller to battery at 12 volts. I use this chart, but there are others around the web.
Voltage Drop Calculator Genuinedealz.com
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Old 28-05-2017, 18:48   #13
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Re: Correct gauge wire for solar panels

I used 8AWG, but maybe 10AWG would have sufficed, since my run was around 20ft with 435 watts of solar power. I would look at the wiring gage recommended by the solar panel manufacturer. I doubt anyone would tell you 8AWG was a mistake. Maybe thinner would work, but I don't think 8AWG is a mistake and you must rip it out to 'fix it'. I used my inverter to check my max amps from the panels. I ran a mini shop vac. It would seem that at midday in Chicago in late May, I was getting 20 amps of input. That was the reduction in the number of amps being pulled by the shop vac, the battery voltage being the same in both runs. The voltage over the wires from the panels is higher, so the amps over that wire run would be less.
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