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Post by spiderbob on May 21, 2015 20:50:22 GMT -8
OK, so I have two 100w mono panels, that I just bought from Renogy, along with a MPPT20CC charge controller. It's function is to keep my batteries charged while I'm away from my fifth wheel trailer. I'm wiring my panels in parallel so if one panel gets some shade I still have the other picking up and delivering 100w, in theory. But this tells me that I should space the two panels apart as much as I can to give me a better chance of keeping at least one in the sun all the time.
Am I seeing this wrong, am I doing the right thing by spacing them out?
Bob
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Post by Admin on May 22, 2015 14:22:23 GMT -8
Hello spiderbob,
Spacing the panels out will isolate shading more and ensure that shade located around one panel does not reach the other panel. One thing to note is that as you increase spacing, you are increasing the length of wire, so you always have to be aware of voltage losses and keep them to a minimum. We generally try to size our wires to have a maximum of 5% voltage loss.
For example, adding a 5ft extension cable between each panel and the branch connector will increase your voltage loss by 0.69% each or 2*0.69% = 1.38% total for your system. Not too much, but as the length gets longer the voltage loss will increase.
Renogy Tech Support
SR
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Post by spiderbob on May 23, 2015 6:24:04 GMT -8
Thank you, but I'm only using one set of extensions as opposed to two, I'm extending from side to side so the five is actually more than I need but it is the shortest you offer. So figuring the total dual run of cable (+&-) I am at 30'. Can you give me a voltage loss? I have 12AWG wire. I do not have my system hooked into a inverter, it is only for charging the two 6v batteries I have in series for 12v.
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Post by Admin on May 28, 2015 12:17:32 GMT -8
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Post by spiderbob on May 29, 2015 6:45:21 GMT -8
OK, so given that you try to only have a loss of 5%, how can I improve this number?
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Post by jsb2000 on May 29, 2015 7:02:58 GMT -8
OK, so given that you try to only have a loss of 5%, how can I improve this number? Go to the calculator in the link and play with the settings. Basically, your choices are to go to a lower wire gauge, shorten the distance, or change the wire type. You also should consider whether the cost of making the changes is worth it. Sure, you could switch to silver wires to get to just under 5%...but I wouldn't! |
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Post by spiderbob on May 30, 2015 5:45:32 GMT -8
Well, shorter I might be about to do. As I'm wiring in parallel I could switch to series that would shorten about 8 feet right here, But I don't think I want to do that as it would not accomplish what I intend to do by having the panels split for shade purposes. So yes, I believe I could get to five but I would be doing it at a loss. I did play with the calculator, I'm installing starting on Monday. I can move the panels somewhat on the roof of the RV, and possibly lose about 3 to 5 feet that way and that would get me closer. I'll see how it works out leaving it in parallel and just reducing as much as possible in wire. If I'm not happy, I can then change it to series quite easily.
thanks
Bob
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Post by spiderbob on Jun 1, 2015 16:44:52 GMT -8
OK, I need a bit of help with the calculator, Install is finished, I wired in parallel and cut the extender cable to 18' 6" overall. The battery cables are 18" long. I have two 100w panels. But some of the info the calculator wants I'm not sure of.
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Post by jsb2000 on Jun 2, 2015 8:06:57 GMT -8
OK, I need a bit of help with the calculator, Install is finished, I wired in parallel and cut the extender cable to 18' 6" overall. The battery cables are 18" long. I have two 100w panels. But some of the info the calculator wants I'm not sure Which info in particular? |
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Post by spiderbob on Jun 2, 2015 15:10:33 GMT -8
What my loss is?
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Post by jsb2000 on Jun 2, 2015 16:45:28 GMT -8
Sorry, I'm confused. You're referring to the Voltage Drop Calculator that Admin referenced, right? In it, you plug in wire material, wire size, voltage, phase, number of conductors, distance and load current. It then computes the voltage drop, voltage drop percentage, and the voltage at the end.
I believe that the loss is the voltage drop percentage.
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Post by spiderbob on Jun 3, 2015 8:32:19 GMT -8
Thanks jsb, I finally figured it out. I have a (voltage drop) of 3.28% but I started out at 8%
Home / Other Calculators / Voltage Drop Calculator
Voltage Drop Calculator
Result
Voltage drop: 0.62
Voltage drop percentage: 3.28%
Voltage at the end: 18.28
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Post by jsb2000 on Jun 3, 2015 17:14:45 GMT -8
Excellent! Those numbers should give you a very efficient setup.
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