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27-05-2017, 06:53
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#1
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Registered User
Join Date: May 2010
Location: East Coast USA or out cruising
Boat: Lock Crowther 150
Posts: 665
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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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27-05-2017, 07:19
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#2
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Registered User
Join Date: Nov 2013
Location: Perth, Australia
Boat: Lagoon 450 Flybridge
Posts: 94
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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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27-05-2017, 07:41
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#3
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Registered User
Join Date: Aug 2015
Posts: 474
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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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27-05-2017, 08:55
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#4
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cruiser
Join Date: Jan 2017
Boat: Retired from CF
Posts: 13,317
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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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28-05-2017, 08:29
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#5
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Registered User
Join Date: Jun 2015
Location: Victoria, BC Canada
Boat: Nordic Tug 37
Posts: 121
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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.
-evan
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28-05-2017, 08:37
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#6
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Registered User
Join Date: May 2008
Location: Nova Scotia until Spring 2021
Boat: Custom 41' Steel Pilothouse Cutter
Posts: 4,976
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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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28-05-2017, 09:40
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#7
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cruiser
Join Date: Jan 2017
Boat: Retired from CF
Posts: 13,317
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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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28-05-2017, 10:11
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#8
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Registered User
Join Date: Dec 2015
Posts: 523
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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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28-05-2017, 14:53
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#9
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Registered User
Join Date: Sep 2007
Location: Queensland, Australia
Boat: None at present--between vessels. Ex Piver Loadstar 12.5 metres
Posts: 1,475
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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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28-05-2017, 15:00
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#10
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Registered User
Join Date: Jun 2013
Location: Up Qld Coast, near Yeppoon.
Boat: Passport 41, Custom Perry in steel.
Posts: 624
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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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28-05-2017, 16:36
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#11
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Registered User
Join Date: May 2010
Location: East Coast USA or out cruising
Boat: Lock Crowther 150
Posts: 665
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Re: Correct gauge wire for solar panels
Quote:
Originally Posted by Oceanride007
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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That's why the charge controller is as close as possible to the batteries.
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28-05-2017, 18:20
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#12
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Registered User
Join Date: Mar 2013
Location: South Jersey
Posts: 361
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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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28-05-2017, 18:48
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#13
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Registered User
Join Date: Jan 2017
Location: Waukegan - Lake Michigan
Boat: 1979 Islander 36
Posts: 91
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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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