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Old 05-02-2016, 03:56 PM   #1
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Solar - fuses, circuit breakers, switches & wire size

I'm going to start with ...

One Renogy Eclipse 100 Watt 12 Volt Monocrystalline Solar Panel, or maybe their Renogy 100 Watt 12 Volt Monocrystalline Foldable Solar Suitcase.

Since the panels are going to be portable, I'll be using the SB50 SB Series 50 Amp Anderson Powerpole Kit as my quick connects.

Trimetric 2030RV Battery Monitor with 500A shunt
SC-2030 Charge Controller with temp sensor.

I have (2) 6V gc batts already.

What fuses/circuit breakers and/or switches do I need and where do I put them?

I know I need a fuse between the battery bank and the charge controller but what size?

Should I have one between the panels and charge controller? Again, what size?

Do I need to have a switch between the panels and quick connect or does the Anderson Powerpole cover that need?

On wire size - what should I use from the panel to the charge controller and also from the charge controller to the batteries?

Thanks all
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Old 05-02-2016, 04:06 PM   #2
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If you are never going to have more than 100 watts, you can use #12 wire to the connector, to the SC2030 and to the battery bank. You can put 20 amp fuses on both sides of the SC2030. You will never get that much current but the wire can handle that much safetly and the fuse is to protect the wire.

Personally I would use #10 just to give yourself some headroom for the future. Of course it does matter how far the 2030 is from the batteries, but the most you will ever see is 5 amps or so from the panels and to the battery bank under normal circumstance.

You probably could use the 100 AMP shunt on the Trimetric, but that depends on your RV loads and not the charge current.
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Old 05-02-2016, 04:43 PM   #3
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I didn't realize I could get away with such small wire. I was thinking about 6 or 8 awg. The CC will be within 5 ft of the batt's.

Do I need to have a switch between the panels and the quick disconnect or is "pulling the plug" while live OK for the system?
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Old 05-02-2016, 04:58 PM   #4
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Pulling the plug is fine...just like a switch. 5 feet is nothing. Its about the amperage and the most you will see from 100 watts is 5 amps or so. The voltage on the panel side is generally higher than 12 volts, sometimes as high as 17 volts. The SC2030 gets it voltage reading from the TM-2030, which is connected directly to the batteries with a very low current lead. Generally the SC-2030 is working hard to keep the voltage down to 13, 14 or 14.5 and it will just up the voltage a little to allow for any drop in the line between the 2030 and the batteries. If you are thinking about the future, use #6 between the 2030 and the battery bank, especially since you are so close. It will handle the full 30 amp current that the 2030 can manage and will leave to room to go to 30 amps from the panels (450 watts or so.)
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Old 05-02-2016, 04:59 PM   #5
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100 watt panel at 12 volts DC will produce roughly 8.3 DC amps.
The panel may put out a bit more than 12 VDC and if does your amps will go down proportionately.
12.5 volts =8 amps
With that you really don't need very large wires.
Look at the size of the wires coming off the panel and continue that on .
I just read your spec sheet on the panel and it can get up to 21.2V. Open voltage
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Old 05-02-2016, 05:31 PM   #6
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Looks like you will never see more than 6.1 amps (cold day, perfect sun angle), but no matter, they use 12 ga from the panel to the pigtails, if you will never use more than one panel you can stick with 12, if you ever expand to more than one you will have to hook them up in parallel and the current will increase commensurately. #10 will give you some headroom as I indicated.
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Old 05-02-2016, 09:30 PM   #7
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You may find the Jack Mayer web site helpful to plan your wiring ,etc. 6 ga wire is best if you eventually plan to increase the number of panels for boondockin. Your batteries are probably 200-225 ah capacity. 50 % draw per night mean you will likely need 300 watts of panels to reliably get 100 ah charge. (400w if your family needs to charge 3 iPads and 3 phones daily like us) . I used 40 amp breakers before and after the controller. Bought on Amazon. Located the breaker to the controller in the battery compartment where it is handy to disconnect with the press of a button. I have eclipse panels, they will put out slightly more than the rating.
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Old 05-02-2016, 09:41 PM   #8
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I'm with previous poster, I would terminate a thin solar panel lead wire(s) as close as possible and go with as large gauge wire as possible/feasible. 6 gauge is what I use from my combiner box which has 4 10 gauge wire from the panels.

10 gauge will get you a .6% voltage drop at 5 feet, 12 volts, and 7 amps. I wouldn't go thinner.
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Old 05-03-2016, 07:42 AM   #9
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Quote:
Originally Posted by johnm1 View Post
I didn't realize I could get away with such small wire. I was thinking about 6 or 8 awg. The CC will be within 5 ft of the batt's.
...
I think that all of the comments so far are correct, we are just talking about the scale of the installation. You are talking about a portable 100 watt trickle charge system, some of the commenters are talking about 300 or 400 watt permanently installed systems.

As I said, in your case the panel already has 12 ga wire and you can use that or 10 ga to the charge controller. The wiring from the panels carries exactly the same amount of current as do the wires from the controller to the batteries, which in your case if 5 feet away. The combiner that other's have mentioned is a box that takes the current from more than one panel and parallels them on a single feed to the controller. If you are using a portable system the wiring from the panel will definitely have to be re-run if you ever switch to parallel panels and a permanent installation.

As a compromise to upgradeability I did suggest that you use #6 from the controller to the batteries since that is a short run, you don't care about cable flexibility (it is totally inside your RV) and the cost would be insignificant for 10 feet of #6 cable. It just means that if you move to a permanent system with more panels you can leave that wire in place and it will support the full 30 amps that the SC2030 is capable of. You can even fuse it at 40 amps so that you don't need to change it if you go bigger.

12 Ga is fine from the panel as long as you aren't putting it too far from your controller, although even that wouldn't be that much of a problem since the PWM 2030 controller is going to be reducing the voltage for the batteries most of the time. You can use 10 ga if you like as that is a pretty standard PV wire from panels. Forget about the voltage drop between the controller and the batteries since the TM-2030 will get the SC-2030 to correct for the voltage drop anyway, and if you use #6 it will be insignificant.
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Old 05-03-2016, 08:49 AM   #10
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Thanks all - the help and learning is very much appreciated!

Like I said in the OP, I'm going to start with (1) 100W panel, etc.

The RV is all LED lights, we have a Mr Heater heater to take the chill off in the evening and then again in the morning, so no furnace needed, "Navy" showers so pump runs minimum amount of time, fridge/water heater on propane (obviously) and a couple of Maxxair fans that might be used for short bursts to cool down if needed .. but we also have a TH so I can just open the back of the rig if it get's too warm! And we have a couple of fans that move a fair bit of air that use rechargeable D batteries. We won't be using 120VAC stuff so that reduces the system size but then I'll need to go larger due to the shade potential. Do they offset each other ????

This endeavor is intended to get my feet wet with solar and not scare myself (or the wife ... or the bank account) by purchasing the "wrong" items and have nothing to show for it (as in: the system doesn't do what I expected).

BTW ... I plug into a 30A RV outlet at home 24/7 while not using the rig so the batt's get topped off between each trip (yes, I maintain the water level in the batt's. I'm also considering replacing the WFCO with a Boondocker. And I have (2) 2000W Champion Invertor genny's, with parallel kit, if needed but they're still noisy, heavy and use a fair bit of gas. But I run out of beer as well so it's a good excuse to run to the store!

I don't yet know how large I'll need (aka - want) to go but I'll probably need to go with a couple of more batt's and 2 or 3 100+ watt panels on the roof and maybe keep 1 or 2 portable as well.

I'll probably go with no smaller than 6 gauge from the CC to batteries since it's a short distance and just in case we change our minds on power usage. And then maybe go with 10 or 8 gauge from the panels to the CC.

If money were no object, I'd plaster the roof with panels and have the biggest bestest charge controller and load the thing with batteries. But sadly ... I don't have that money.

Does this seem like a reasonable plan or have I missed the boat?
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