russ
Solar Advocate
Posts: 63
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Post by russ on Aug 18, 2019 18:28:41 GMT
Now I have to think about how to have the two CC units tied into one Load point. Why do you want to connect the charge controllers to one load point? Do you only have one load?
Your Rover with the four 100 watt solar panels should be connected to the 100 AH battery.
Your PWM charge controller should be connected with the two 50 watt solar panels to the flooded car battery.
The two systems should be separate.
Greater loads can be applied to the 100 AH battery. (Assuming this battery is in good state of heath it can be discharged up to 50 AH or 50 AH x 12.7 V = 635 watt hours. For example: a 100 watt load for 6 hours, or a 50 watt load for 12 hours.)
Light loads can be connected to the flooded car battery. (Keep in mind that a flooded car battery is not designed for deep cycling. The battery won't last long if you cycle it very deeply.)
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russ
Solar Advocate
Posts: 63
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Post by russ on Aug 18, 2019 18:35:18 GMT
Since I have six panels, I have 12 wires coming in, and I have a fairly heavy duty terminal block where the wires are connected. At one end of the terminal block I have two diodes, one on the +, and one on the -, that plug into a quick connect. The other side of the quick connect I have the two wires going into CC panel connect. The diodes, if I remember correctly are rated at 30Amps/1000V. So at this quick connect point, I guess, I will be able to contrive some kind of fuse connection. [...] The wire that comes from the panels is the wire that I bought from Renogy, which is 10 gauge, I believe. Now the wire that I have that connects between the terminal block and the CC which is on about 6" in length, is a 14 Gauge, which I am now going to change to a 12 gauge. I do not have any 10 gauge wire, so I will see if the 12 gauge does the trick. If I understand you correctly, you have 12 wires of 10 AWG, two from each solar panel, connected to a terminal block.
How long are each of those wires?
Why do you have diodes at the terminal block?
What size and length are the wires going from the charge controller to the battery?
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Post by tattoo on Aug 18, 2019 18:43:03 GMT
The 14 gauge, which is in there now, is solid core. No wonder it's getting hot.......... |
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Post by tattoo on Aug 18, 2019 18:46:36 GMT
Since I have a pwm CC, I might have to separate the batteries and the two 50W panels, and have the pwm CC tied into the flooded battery. Now I have to think about how to have the two CC units tied into one Load point. Have you not read anything people have told you? That was suggested several days ago.......
Ok this is sounding like someone is playing a joke...........
I'm done here...........
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russ
Solar Advocate
Posts: 63
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Post by russ on Aug 18, 2019 18:55:03 GMT
The reason I have my panel pairs in different locations is because of shading. I will probably try to angle the panels at 55*, this will be about the best angle for a winter angle and probably an all year position. Yesterday I noticed that some of the wiring going into the CC was getting very hot, never noticed that before, so today I have to rethink my wiring, and try to rewire if I have the materials. In the conversations so far I have noticed that you guys are using fuses, I do not have any fuses anywhere. I made an assumption that the CC would handling that issue. At this point it sounds to me like their would be a need for a solar station fuse box. The wire from the panels going in, passing through breakers, going to the CC. The wire coming out of the CC going to the box, passing through breakers, going to the battery. And maybe somewhere in there some terminal connections for accessing some regulated power, OK now I am awake. Once again, you are substituting guesswork and assumptions for plain old study. There is so much information on the topic of putting together a DIY solar system, that there is no excuse for the things you don't seem to know or understand. My intent is not to be mean, or demeaning, or condescending, but what Mediadog said is very true. Anyone preparing to build an off grid solar power system should begin with careful study of what they need and how they need to configure the system for cost, efficiency and especially for safety!
Ravdas, take some time to read how to correctly configure a solar power system and why it should be configured that way. It is always good to understand how electrical power works. You should absolutely understand Ohms law! There is no need to experiment to figure out what works when you have the Internet at your disposal.
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Post by bupkis on Aug 18, 2019 22:44:41 GMT
so above it suggested 10awg x 4.7A x 20' yielding a voltage drop of .193v www.genuinedealz.com/voltage-drop-calculatorSo the power loss is .193 X 68v or 13 watts panels to CC. @ 17v, 13 watt loss = .765 volts, redo v.d. for 18A x 20' yields v.d. or .739v or ~13 watts! The CC will operate more eff transforming 17v vs 68v esp at low power conditions. The problem with using single parallel panels is panels get hot and Vmp drops. Paired series panels (w/mppt cc) solves that by doubling Vmp to >30v les v.d. With 68 volt input about 13 watts loss due to voltage drop with 10 AWG wire at 20 feet.
With 17 volt input about 13 watts loss with 1/0 AWG wire at 20 feet.
Yes, at the higher voltage input the MPPT charge controller will loose something like 2 to 4 percent efficiently. As long as you can afford the cost |
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Post by bupkis on Aug 18, 2019 23:11:12 GMT
let me fix my math!
10g, 20', 320 watts
.9 watts power loss @ 68v
14 watts power loss @ 17v
14/320 = 4% and there is you 4% to counter the loss of eff at 68v, not to mention what happens at low power!
now the CC lower eff is all the time @ 68v input, the power loss from voltage drop is not all time cuz the input power changes constantly.
it is not an instantaneous issue cuz power production is ever changing.
furthermore the OP's crappy location and panel orientation mean less power ie less power loss!
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russ
Solar Advocate
Posts: 63
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Post by russ on Aug 19, 2019 5:10:29 GMT
let me fix my math! 10g, 20', 320 watts .9 watts power loss @ 68v 14 watts power loss @ 17v Four 100 watt solar panels in series (operating under optimum conditions) 10 AWG copper wire 20 feet one way to complete the circuit. 320 watts theoretical. 320 watts / 68 volts = 4.7 amps (solar panels in series) 20' one way of 10 AWG wire at 4.7 amps = .19 volts (1.56%) voltage drop (.89 watts) An additional 4 % lost do to MPPT convertion at high voltage (320 - .89 watts = 319.1 watts at the charge controller) 319.1 watts * 4 % = 12.8 watts 12.8 watts additional loss from MPPT voltage conversion + .89 watts from wiring voltage drop = 13.7 watts total 320 watts / 17 volts = 18.8 amps (solar panels in parallel) 20' one way of 10 AWG wire at 18.8 amps = .75 volts (6.25%) voltage drop (14.1 watts total) These numbers are based on optimal solar panel performance. As you pointed out, if the solar panels are not placed in a optimal configuration the current can be significantly reduced. As well as the fact that the system load is usually not at maximum. |
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raydas
Solar Devotee
Posts: 166
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Post by raydas on Aug 19, 2019 12:28:03 GMT
Hey, raydas, what is your cable run for the panels. Gee, I am glad you asked, is that important.
My experimental setup:
2 100W south panels, ~50 feet to the CC, 10AWG stranded copper.
2 100W east panels, ~30 feet to the CC, 10AWG Renogy.
2 50W SE panels, ~15 feet to the CC, 10AWG Renogy.
I am still trying to get a good sense as to where theory ends and reality sets in, for a good idea, of what can be accomplished with the given conditions. My setup is experimental, and I am not working with the top of an RV or even a small cabin in the woods, nor am I even considering a roof top. In the long run, I may come to the conclusion that solar power is not the way to go for my specific conditions or even could be used in some lesser fashion.
As to the series model for my setup, not sure if it cost effective or even efficient to consider when the two sets of panels are at least 80 feet apart.
Even having the parallel setup has some problems, especially the 50 foot run. I will probably have to do the math to see what advantage, if any, the conversion to a series would make, in a two panel set, on a 50 foot run.
Yes, I am well aware that solar panel electricity can kill and even cause fires if not used correctly.
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Post by mediadogg on Aug 19, 2019 13:10:32 GMT
Hey, raydas, what is your cable run for the panels. Gee, I am glad you asked, is that important. My experimental setup: 2 100W south panels, ~50 feet to the CC, 10AWG stranded copper. 2 100W east panels, ~30 feet to the CC, 10AWG Renogy. 2 50W SE panels, ~15 feet to the CC, 10AWG Renogy. I am still trying to get a good sense as to where theory ends and reality sets in, for a good idea, of what can be accomplished with the given conditions. My setup is experimental, and I am not working with the top of an RV or even a small cabin in the woods, nor am I even considering a roof top. In the long run, I may come to the conclusion that solar power is not the way to go for my specific conditions or even could be used in some lesser fashion. As to the series model for my setup, not sure if it cost effective or even efficient to consider when the two sets of panels are at least 80 feet apart. Even having the parallel setup has some problems, especially the 50 foot run. I will probably have to do the math to see what advantage, if any, the conversion to a series would make, in a two panel set, on a 50 foot run. Yes, I am well aware that solar panel electricity can kill and even cause fires if not used correctly. 3 sets of two panels would work just fine. ((2 x 100W in series) x 2 in parallel) connected to to the Rover MPPT and the SLA battery. Then the 2x50Watt panels, either series or parallel, connected to a small PWM CC, that charges the auto battery. I think someone else proposed this, a while back. The "real world" always wins. If you apply all the great math provided by the other guys to the configuration I just suggested, you should have a very solid idea of what the upper bounds of your production will be. |
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raydas
Solar Devotee
Posts: 166
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Post by raydas on Aug 19, 2019 13:59:20 GMT
Thanks, I am well aware of some of configuration suggestions that were made. I want to figure out how I can get some figures from my setup, as it stands now, so I can make some reasonable comparisons between different setups. It sounds to me like everybody, here, is sold on the series model, me I prefer to work with low voltages, unless of course it is a real disadvantage, from an efficiency stand point.
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Post by mediadogg on Aug 19, 2019 14:10:45 GMT
Thanks, I am well aware of some of configuration suggestions that were made. I want to figure out how I can get some figures from my setup, as it stands now, so I can make some reasonable comparisons between different setups. It sounds to me like everybody, here, is sold on the series model, me I prefer to work with low voltages, unless of course it is a real disadvantage, from an efficiency stand point. Well then, sorry that I repeated what you already knew. And since the pros and cons of series vs parallel have also been explained many times, I guess I should not have explained (once again) that it is possible to use both. In fact I made my suggestion in direct response to your description of your setup, in an attempt to be helpful. So leave your snippy comments at the door. I'm out. |
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Post by tattoo on Aug 19, 2019 16:30:38 GMT
So leave your snippy comments at the door. I'm out. I've been out.......
I don't know why they asked a question in the first place? They weren't looking for help it sounds like............. |
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Post by bupkis on Aug 19, 2019 16:50:41 GMT
raydas, I do not understand the hostility to you here. Keep up the experimenting and learning. in the mean time there are some great videos from altE that explaine parallel, series, shading, temperature, etc how to wire shaded panels - www.youtube.com/watch?v=ofo1HQyGG8ssubscribe to that one and see many others like using different size panels ... The altE uses real solar to demonstrate solar. This one is just for fun, a 24v panel directly connected to a water pump, then different type of shade is introduced, later in the video he tilts the panel, no meters just a water pump output that is very visual. Seems right up your alley ! www.youtube.com/watch?v=UNPJapaZlCU&t=169s |
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raydas
Solar Devotee
Posts: 166
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Post by raydas on Aug 19, 2019 17:32:39 GMT
bupkis, Thanks. Hopefully they will get bored and dispense their snippy comments somewhere else. I figure if I share my experience, then somebody else might get some benefit.
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