My truck camper has OEM wiring for a solar panel, the problem is that it's only 10awg wire. I don't really want to remove the fridge if i don't have to so I'm trying to figure out the best way to just use this wire. The run is about 8-10 ft to the charge controller.I am currently adding 2 12v 100w panels in parallel but have plans for 2 more.so the questions...1. how many amps can I get away with with the 10awg wire? Could I run them all in parallel or would the loss be too great?2. If I run them in series it seems like the voltage gets pretty high, most DC breakers and switches I've seen (using mostly blue sea stuff) has a maximum voltage of 48V. Do you start using AC breakers once the voltage gets higher?3. Maybe I could run two sets of parallel and then series them together?4. I realize that if I go series that I will need an mppt controller, Are the EP Solar controllers ok? I'd like a better one but it's cost prohibitive to get up here in Canada.Just trying to see if it's feasible to use the OEM 10 gauge wire.

Drop the wires DOWN from the removed cap, vent. I would go #6 AMERICAN WIRE GAUGE, not #6 SAE, size wire.Of course this is for paralleled connected panels and a PWM controller.

How well secured is the existing wire? If it's kind of loose, perhaps you can use it to pull new heavier wires down.Purely from a wiring safety point of view, you can go up to at least 30A and probably somewhat more with 10 AWG wire. Since the voltage drop is proportional to the current in the wire, you lose a lot less power by increasing the voltage where feasible.You should not use AC (only) breakers or switches for higher voltage DC circuits. AC switches and breakers are designed with the assumption that the voltage (and hence current) waveform will have zero crossings regularly, and hence any arcing have a "gap" and a chance for the ionized air to dissipate. DC switching is much harder on contacts than AC switching. Higher voltage DC circuit breakers are available, for example this 3 pole 10A 125 VDC breaker, or you could just use a plain old fuse and possibly a suitable switch or something (maybe a knife switch) since you presumably won't need to be disconnecting the solar panels frequently.

how many amps do those panels put out? isn't 30 amp adequate?bumpy

#10 is good for 40 amps if you are not concerned about voltage loss.I would have all four (same panels) in series to an MPPT controller.

Could you use 2 x 12 volt in parallel (double current), plus 2 x 12 volt in parallel, wired as 2 x 12 volt pairs, wired in series? Use a MPPT controller at 24 volts, with the 10 gauge running at 24 volts and only the amps of a a single pair in parallel?Single panel Amps * 4 / 2 pair in series = 2 x panel volts and 2 * panel amps.Please don't take any advise from me unless you check it yourself and take ownership of the idea......

Parallel vs Series, 10awg wire | Good Sam Community

27 Replies

hedge
Explorer
Jun 14, 2016
I'd like to thank all of you for the insight and for answering my questions. I got the system installed on the weekend and it all seems to be working fine. Hard to say how much I'm getting out of it yet as my battery is pretty much full. I hope to give it a better test this weekend.
Almot
Explorer III
Jun 13, 2016
Length is important, but he said it's 8-10 ft to controller.

At this length, with 2*100W panels, #10 @11A will have voltage loss well under 2%.

4*100W in parallel require a thicker cable. Or go series with MPPT controller.

Yes, manuals of decent controllers over 20A suggest fuses both before and after. I chose to ignore panel fuse. Wire can carry more current than panels will ever generate. My roof is rubber, on a dry day there is nothing to worry and on a rainy day there won't be much current. My 24V panels in series never generate more than 8A total. 12V panels in parallel is a different story though.

Human body doesn't usually like currents over 1A. If anybody could explain why a short to ground may not happen at all, I'm listening.
MEXICOWANDERER
Explorer
Jun 13, 2016
I tried theoretically correct 10 gauge wire on Quicksilver. 46 total feet. That install lasted maybe 11 seconds before the 6 gauge was unrolled. Do the math and multiply say 12 watts times say two thousand hours. Ooooooooo painful isn't it?
JFNM
Explorer
Jun 13, 2016
I probably missed it but the length of the wire is important to calculate voltage drop. I'm running my 650 watts solar down #10 wire for about 25' at 60 volts so what you are thinking of doing is certainly possible. I have a Morningstar MPPT charge controller with which I am very happy.

I have fuses in the charge controller input and output cables. IMO, it is more about attempting to protect the controller from "odd conditions" (e.g. lighting strike) than anything else.
2oldman
Explorer II
Jun 13, 2016
ewarnerusa wrote:
So this is a reason to install a circuit breaker or fuse between the panels and controller. For convenience, not safety.
Yes, I do have a switch for such purposes.
pianotuna
Nomad III
Jun 13, 2016
No fuse needed--but a switch is a good idea.
ewarnerusa
Nomad
Jun 13, 2016
2oldman wrote:
hedge wrote:
Why no switches or fuse? I had planned on doing both
If you can explain why fuses are needed between the panels and controller, I'm all ears.

In my situation, my Morningstar Tristar controller is programmable. In order to complete a reprogram, the controller must be reset by cycling power to it (interrupting the the power connection between the controller and battery). Since you should not have the controller hooked to solar input when it is not hooked to a battery, I must first disconnect the panels from the controller before cycling power to the controller. So this is a reason to install a circuit breaker or fuse between the panels and controller. For convenience, not safety.
wa8yxm
Explorer III
Jun 13, 2016
12 v 100 watt panels that would be what, 8.x amps, Times 4 would be about 37 amps, bit much for 10 ga, but those panels hardly ever deliver full output, if ever. so you can at the most expect around 15-20 amps out of 'em, well within 10 ga,, however for solar panels you want heavier wire to reduce voltage loss.

What I would do

See if that wire will move up and down in the path. If so use it like "Fish tape" and pull heavier wire if you can. If it's stapled.. Oh well.. You tried

Yes you can use it, but a larger wire will give better charging, or double the wire, However double the wire will need a bigger hole. (Or a Much bigger hole).
time2roll
Nomad
Jun 13, 2016
The wire from panels to controller will generally have the capacity to carry twice the maximum panel amps (Isc).
Go ahead and short the wires all day... nothing will happen.
DrewE
Explorer II
Jun 13, 2016
hedge wrote:
2oldman wrote:
hedge wrote:
Why no switches or fuse? I had planned on doing both
If you can explain why fuses are needed between the panels and controller, I'm all ears.

well I'm new to this trying to learn but I thought if you had current running through a wire then you always wanted a fuse to protect the wire from catching fire. A fuse is also specified in the instructions.

what's the theory behind not needing a fuse?

I suspect the theory is that the solar panels are inherently limited in their current supply capabilities. If they are incapable of supplying more current than the wire can safely carry, then the fuse doesn't serve much of a purpose.

I suppose that theory might break down if you happened to park under a giant fresnel lens or (less unlikely) next to some reflective building or other structure that increased the intensity of the light on the panel beyond nominal sunlight. I personally would rather have an unnecessary fuse than omit one that turns out to have been necessary.