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Old 01-17-2017, 02:48 PM   #21
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Which solar controller?

What is the total length of the wire?

Use this online calculator.

http://www.calculator.net/voltage-drop-calculator.html

It will also depend on whether you wire the panels in series or parallel. I did another post with calcs for loss for 10 gauge wore basss on 10 got wire increments.
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Old 01-17-2017, 03:24 PM   #22
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What are your variables in the calculator? 100w = 5.7 Amp X 17.5 V These were one of my assumptions based on 100 W panel at output of 17.5 V. Is this the right approach?
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Old 01-17-2017, 04:18 PM   #23
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Glad to hear Gary was satisfied with EPS because I am considering them for the batteries and BMS because of availability and cost, and going with Renogy Eclipse panels and Victron for everything else. Now thinking I'll go with the Victron MPPT 100/50 over the 100/30 for an extra $100 to allow room for expansion. Think I decided to scrap my two 50 W factory panels and sell them here and go with four Renogy Eclipse panels in a series/parallel arrangement which should keep voltage loss at an acceptable level with the factory 10g wire. I am thinking of making my own mounts from flat aluminum stock because the mounts for sale seem expensive for what they are and this way I can customize their length to level the panels.--Frank
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Old 01-17-2017, 05:15 PM   #24
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Little54,

Depends on whether panels are series or parallel. If parallel, the amps are additive, if series, the voltage.

So if series, you would multiply the volts per panel times the number of panels. For parallel, multiply amps per panel by number of panels.
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Old 01-18-2017, 05:52 AM   #25
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Here is one an example of the many voltage drop calculators. I use 3 panels in series on the curb side pointed south no shading. Also have had up to 900 watts on the ground for a total of 1200 watts. This produced a peak of 840 watts to the battery and at times peaks out my 60 amp charge controller. My system operates around 45 volts at Maximum power point and on sunny days. My entry of 22 amps for current is on the high side and typically would be below 20 amps.
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Old 01-18-2017, 06:51 AM   #26
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Frank if you make your own mounts out of aluminum, I would love to see how they turn out
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Old 01-18-2017, 09:41 AM   #27
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Originally Posted by fran&frank View Post
I am thinking of making my own mounts from flat aluminum stock because the mounts for sale seem expensive for what they are and this way I can customize their length to level the panels.--Frank
Renology has a stainless mount that also works well and isn't too expensive.
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Old 01-18-2017, 09:58 AM   #28
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Dolcinabox how did you figure your loss using the 10 ga wire? I have the Victron 100/30 and I have the prewire shown my Troutboy which is 10 ga. I want to run 2 100 AM panels and would love not to rewire!! Been convinced to this point to go 6 ga due to the length of wire run when you calculate with out and back. 2016 22fb Sport the Zamp combiner box is at the rear and my Victron up front.
Let's assume your wire length is 40 ft, 20 ft for two conductors. #10 AWG has a wire resistance of 1 milliohm per ft, so the resistance of your wire is 40 milliohms. If you wire your panels in parallel, the voltage will be 17.7 V and the current will be 5.6 A * 2 = 11.2 A. So the losses due to the pre-wiring will be 11.2 A * .040 ohm = .448V, or .448/17.7 = 2.5%. If you wire your panels in series, the voltage will be 17.7 V x 2 = 35.4 V and the current will be 5.6 A. So your losses due to the pre-wiring will be 5.6 A * .040 ohm = .224 V, or .224/35.4 = 0.6%.

Even though the losses are greater in the parallel configuration they are still somewhat negligible and anecdotally most folks will say parallel panels work better. The issue depends on the design of the solar panel and whether or not it includes bypass diodes and also how quickly the MPPT controller can readjust to a new operating point. There's some stuff on the web that consistently shows the parallel configuration to be better than a series configuration. I've been unimpressed with most of these tests. Your mileage my vary.
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Old 01-18-2017, 12:36 PM   #29
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When all the theoretical considerations are done, one has to look at the practical ramifications. In a 200 W system I don't see where anyone can tell if they're missing a few extra watts. That is assuming there is no shading on the panels. As systems become larger and larger, placing panels in parallel becomes more restrictive because of the larger current and more expensive/complicated bc of wiring.
Shading in series systems is a real problem. So in an environment such as RVing or sailing, where there are plenty of shadows, it can be a less efficient way to organize your solar panels. So, I understand why many installers suggest pure parallel arrangements. It allows a customer who does not want to fuss with panels to have slightly better power output than a series/parallel system. If one doesn't mind adjusting his panels, tilting them, clearing them from shadows, deploying them on the ground, series/parallel systems allow more flexibility and scalability.
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Old 01-18-2017, 09:10 PM   #30
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Thx for all the info docinabox. The 2017 is set up a little different. It has the big zamp connector I posted above and a white toilet vent. In addition, with the street side awnings, I think I have less room. I like how you extended the panel height with the metal or aluminum square, to raise the one side. I think I can ge three on that side like you, and for one in front on other side where yours is, and maybe one in back for the 500. Here are some of my roof shots:

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I was also reminded by someone that you need to leave roof access, but I guess you could unscrew the panels to access as needed for maint.

Also, Alano, I ran the losses for your scenario above and get much higher voltage loss, 5.03%. So not sure if the calculator is wrong.

The real sensitivity is in the amps. If you have 5-6 100 watt panels on top, then you have 28-33 amps if in parallel, and the losses get huge for 10 AWG, 12.5% or 15%!!!! For a 20 foot run. This would drop your input volts at charger to 15V or lower....

I think bugger wire is best if you have more than 200W and you want parallel.


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Old 01-18-2017, 09:42 PM   #31
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Thx for all the info docinabox. The 2017 is set up a little different. It has the big zamp connector I posted above and a white toilet vent. In addition, with the street side awnings, I think I have less room. I like how you extended the panel height with the metal or aluminum square, to raise the one side. I think I can ge three on that side like you, and for one in front on other side where yours is, and maybe one in back for the 500. Here are some of my roof shots:

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I was also reminded by someone that you need to leave roof access, but I guess you could unscrew the panels to access as needed for maint.

Also, Alano, I ran the losses for your scenario above and get much higher voltage loss, 5.03%. So not sure if the calculator is wrong.

The real sensitivity is in the amps. If you have 5-6 100 watt panels on top, then you have 28-33 amps if in parallel, and the losses get huge for 10 AWG, 12.5% or 15%!!!! For a 20 foot run. This would drop your input volts at charger to 15V or lower....

I think bugger wire is best if you have more than 200W and you want parallel.


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Also remember that your cable run has to include the lengths of BOTH WIRES as your true circuit length is the round trip of both the positive AND negative cables.

Also, you can order some extra tall feet for use along the outside rails to keep your panels flat on your roof. You can also replace those tall roof vent terminations with shorter versions that fit nicely UNDER your panels. Look up '360 Vents' from Lippert!

PS: What's that white stuff all over your roof?????
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Old 01-19-2017, 09:49 AM   #32
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Lew if you look at the calculator Troutboy is referring to it calculates the double run and asks for only one way Distance as the input variable I believe. (see screenshot of the calculator above) I didn't see it at first.
This thread has been really helpful. With no background in solar electronics it takes a few explanations a few different ways for things to sink in.
One of the concepts I'm still not clear on is the step down accomplished by the controller. The controller drops the V down to a level acceptable for charging the battery appropriately. What happens to the amps? It's amps in that we want right? So if the V is dropped by the controller are the amps increased or is there also a proportional drop? Do the amps stall the same?
I can't wait to get the panels mounted to begin the real world experience. Kinda cold and major wet in the NW right now.

(Sorry if this posts twice, didn't see it in my feed this AM. Sometimes there seems to be a lag in posts showing up)
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Old 01-19-2017, 08:21 PM   #33
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Looks like the zamp port would be in the way of rear transverse panel. Yes if you want to place 500 watts on the roof, I think parallel would be the way to go. An example of series/parallel arrangement would include 300 watts series on curb side and a ground deployed 300 watts. This would allow you to use the 10 awg prewire with little power loss. Or you could do a series/parallel arrangement with 400 watts. Otherwise be prepared to run some heavier wire.
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Old 01-19-2017, 08:32 PM   #34
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This is my attempt at avoiding shade.
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Old 01-19-2017, 09:11 PM   #35
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I may remove that zamp port altogether. That looks pretty cool. How does it work? How do you deploy them, carry a ladder?
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Old 01-19-2017, 11:51 PM   #36
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Just some tilt bars. Yep I always carry a step ladder in the bed of the TV. Still working on tweaking this system. Btw tilting greatly increases output in the realm of 30% and probably more bc in the "stored position " the off side tilts away from the sun. In addition shading is greatly reduced. I'm also hoping that these two arrays, when stored and during travel, will provide enough power to run my refrigerator 100% solar.
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Old 01-20-2017, 06:05 AM   #37
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Doc,

When you camp with the arrays set like that, is there an optimal way to park, with that awning side facing south?
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Old 01-20-2017, 07:01 AM   #38
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Just point it south. One could use a compass to get a rough idea of solar noon. Of course if you are restricted to a campground space, your position is fixed in most likely a less than ideal position. This is why I like using ground panels because they can work with any scenario. You can point them at the sun regardless of trailer position.
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Old 01-20-2017, 12:20 PM   #39
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Also, Alano, I ran the losses for your scenario above and get much higher voltage loss, 5.03%. So not sure if the calculator is wrong.

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Here are the two scenarios and results...

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I've been wrong before, but it's always worth double checking.

BTW I've got 400W on the roof in a series/parallel arrangement in 30' Classis and my voltage losses due to the pre-wiring are less than 2%.
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Old 01-20-2017, 02:08 PM   #40
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Alano, I was using 40 feet, not 20 as I missed the note saying use one way distance, not double. Sorry for the confusion


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