Ok, ready to install my solar system and I need to buy wire to go from panels to the solar controllerTwo, 140W panels, wired in parallelHere are the specs on the panel:The wire length of run from panels to controller will be 30-35'I'm a bit confused on wire size......Also, do these panels need to be fused at the panels? If so, what size fuse.I really appreciate all the help this forum has afforded me over the years. Hope to repay it someday.

see page 5 of 16, 4 gauge (36') for 20A (Isc *2, 8.48A * 2 = 17A)http://www.bogartengineering.com/sites/default/files/docs/SC2030-7-6-15-UsersInstruc.pdfA circuit breaker with the ability to turn off is a good idea so the panels can be turned off at the controller when needed.

10 gauge wire seams to be about the best compromise between cost and loss, 8 gauge would be better for the length of run you have but 10 gauge will work fine. 4 gauge is probably the best and if you have the cash to run 35' of 4 gauge which will require 70 total feet of wire then go big. Basically it comes down to how much line loss is acceptable for the cost of the wire.As for the fuse I would put a 40 amp inline fuse at the controller if for the only reason to have a way to disconnect the solar panels from the controller and batteries. Its nice to be able to disconnect the solar input if you need to take the batteries off the trailer for any reason like I had to do when I took my trailer into the shop for front wall work and I knew they would have to remove the batteries to do there work. With my controller the battery's need to be hooked up before the solar panels or the controller may be damage, well you know the guys at the shop don't know this and if they did they probably wouldn't do it right anyway. Its sure easy to pull a fuse right at the controller then getting on the roof to disconnect panels or pulling the wires from the controller plus a fuse is always a good idea.

You don't need anything between the panels and controller except wire, and a separate 10ga or at least 12ga for each panel will be fine. Your voltage loss on the panel side will not be noticeable.

This is why I'm confused......Some folks are saying 4ga wire and other are saying 10ga wire. The place I bought the panels (AltE) said 10ga would be fine for up to 50'. But then I read that you need 4ga for 50' at 20-25amps...........But, will these panels really put out 20-25 amps? That's the part I don't understand.

The hard core tech guys are going for as little line loss as possible between solar and controller. Your panels might in the perfect world, sun at perfect angle and perfect temp hit there max of 25 amps at least for a minute or two.I understand your confusion as I just went through this as well. I have 200 watts on my trailer roof and 35 to 40 feet of 12ga wire to controller. Controller is about 6 feet from batteries with 4ga wire. I have a 20 amp inline fuse at controller and 40 amp fuse between controller and batteries. The kit I purchase came with the 12ga wire, if I knew what I know now I would have purchase a roll of 10ga twin lead from e-bay and used that. I now have a roll of the 10ga and will rework my wiring when I decide to put 2 more panels on the roof. The 40 amp fuse between controller and battery was in anticipation on have 400 watts of panels but due to other trailer repairs I haven't purchased them yet and I am wondering if I really need another 2 panels. My 2 week trip the end of the month will be the deciding factor on the other 2 panels.

Solar Wire Size..??? Fuses on panels...?? | Good Sam Community

Rbertalotto
Explorer
Sep 08, 2015
Well how about that. You learn somethimng new every day. I didn't think the resistance in a 18" piece of #2 wire would add up to anything on a two battery system. Although extremely small, it is still there.

I'll be moving the negative wire to the far battery as stated here.

http://www.smartgauge.co.uk/batt_con.htmlhttp://www.smartgauge.co.uk/batt_con.html

Thanks for pointing it out.
Rbertalotto
Explorer
Sep 08, 2015
Why do you have 2 + and only 1 -

This system used a Bogart Trimetic monitor. This is how it is wired. The house load negative (-) and all other negativeness go to a shunt mounted in the trailer. Therefore only one negative wire to the batteries. At the shunt, the negative from the solar controller and the house negative on one side and the other side of the shunt goes to the negative of the battery pack.

The 3 positives are from the solar controller and from the house positive and from the second battery.

With every negative going through the shunt, the Trimetric can "READ" all current going into and out of the battery bank.
grizzzman
Explorer
Sep 08, 2015
Rbertalotto wrote:
The batteries are wired in parallel. I didn't think it mattered where I connected my + and -. I simply went to the closest battery.

In a "series" connection you would need to connect to the "beginning" and the "end" of the series, but in parallel I don't believe it matters.

Someone correct me if I'm wrong.

Your wrong.........You can stand corrected :)
Johnny_G1
Explorer
Sep 08, 2015
I may be wrong but balance is better, looks like you will be drawing all your power from the one battery, I have 8 batteries in my rig since 2003 and they are still right up there with a hydrometer, worth a try. Just my thought's.
MEXICOWANDERER
Explorer
Sep 08, 2015
pianotuna wrote:
Muddy,

Some of us are power hogs! I use up ever watt my solar panels produce and then some.

Power Hogs?

I RESEMBLE THAT REMARK!
(oink, squeal, snort) :) :) :)

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