Suggestions wanted for connecting four 100w panels

idealy speaking. solar should be in series. fused between solar connection and charge controller. fuse between charge controller and input charge for batteries. perfect setup would be all battery connections the same length, connected in a centralized point with a single output to inverter. fused between inverter input. if you connect batteries as shown one battery will always have full power. the others will always lag in output or in input. you can buy fuses at automotive, marine stores and of course renogy. for more info, renogy is there to help just ask buy calling or emailing or in there forum.

what we do here is we have 3 battery chargers hooked up to our system for extended periods of no sun. we have had only 4 days in 21 days of more than 4 hours of sun(less than .2 amp charge)2 are 2.5 amps and 1 7.5 amps. which is still not max on charge input. hook battery charger to generator and charge away. its a misleading amp output on most battery chargers. you need to test your amp output of battery charger to make sure don't over charge batteries. ours says 50 amp and only get 7.5. they say 20% of ah is ideal?
when hooked in series/parrellal you will have a percentage loss of amp according to length of wire. its less if in a series. there is a web sight that is in more detail. I don't know the name.
when power is drawn from just the first battery connection its that battery that gets the most charge/discharge. all other batteries in that parallel/series will always lag. in renogys forum(system show and tell) I posted a picture of what is called centralized charging/ discharging. its kinda mind bogling but its the best way if possible.
we live off 12 volt power theirs no way around it. but solar panels hooked in a series powering renogys charge controllers it knows we have 12 volt battery hook up. 4 into 1 or 2 into one, here at home its 4 into 1 with 80 volt dc output and 12 volt charge to batteries. confussed?
here we run generator-battery chargers-heat-lights- power tools-etc. when generator is running, and hope to god renogy doesn't fail us on sunny days when no generator is needed.
the forum will be under diy junk parts solar.

Hello Sir,
I am glad Oscar was able to assist you. Please give us a call back if you have any other question. Have a great day!

How are you using the solar array, is it RV use or Cabin use? If cabin why are you doing a parallel wiring, why not go series? If RV, I also used a parallel wiring configuration, the reason, if I get shaded by sun movement on one panel, I don't lose such a large amount of charge rate. I was told that the fuse should be equal to the controller. I agree you have a safety factor by reducing the amaperage of the fuse, but perhaps 10 amps less is a bit too much.

rockhillwill:
I hope this helps at least in the 12v area of WIRING SOLAR PANELS IN PARALLEL vs. IN SERIES

One of the big decisions for a solar power installation on an RV or CABIN style is whether to wire the solar panels in series or in parallel. There are several things to consider when making this decision. When the solar panels are wired in series, then the developed voltage across all the panels is additive while the current remains constant from panel to panel. Thats to say, if there were four 100 watt 12 volt panels producing ~7 amps each, then the developed voltage across all the panels would be 48 volts (12 x 4) while the current would be just ~7 amps, I don't have the spec sheet in front of me for Renogy 100w panels. When the solar panels are wired in parallel, then the voltage of the panels remains constant through the circuit while the current is additive from panel to panel. An example, for those same four panels (400w system, 4 - 100w panels x 12v @), the developed voltage across them would be 12 volts but the current would be 28 amps (7 x 4). Again, I don't have Renogy specs in front of me to say they are 7amps. Please understand that that figure, 7 amps, will only happen when the sun is straight over the panels, more on that latter.

The solar charge controller takes care of balancing everything out by ensuring the circuit between it and the batteries is always 12 volts on the output. In the case of the above solar panels wired in series, the solar charge controller steps down the voltage from 48 volts to 12 volts (if they are 12 volt batteries). The current then increases from 7 amps to 28 amps in the wire run going between the solar charge controller and the batteries. In the case of the above solar panels wired in parallel, the voltage is already 12 volts, so the solar charge controller does not need to step it down for the batteries. The controller is the brains of the whole operation, Every company puts different perimeters into there charge controller. Mine from Renogy is a 40 MPPT, but you can buy them into the +100 range depending on your needs. As to fuse, your using a 40MPPT it is good to 40 amp. I was told in the last few days that a 40 amp fuse is the max. So I use a 35 amp fuse as safety barrier. You use a 45 amp fuse and for instance, you could burn up the controller only rated at 40 amp. You need to figure the battery size depending on your use.

You still have not said what your intention is with the system, i. e., OK, so it's for a cave, but how many amps are you intending to use, what kind of inverter do you intent to use and how may watts do you intend to use for how long. To simply charge two batteries with an array of panels is easy with no specs to follow it. Unless that is your intention, just to charge batteries?

As to why I wire mine in parallel, when solar panels are wired in series, if shade hits one panel and shuts it down (caused by that solar panel’s internal circuitry building up a massive amount of resistance), then the entire string of solar panels shuts down to a certain degree, and usually quite large degree. For instance, if a tree shaded 1/3 of one solar panel in the string of four panels given above, wired in series, the current production of the entire array of four panels would be reduced to almost 0 amps, even though the three other solar panels were in full sun.

As to parallel, if the panels are wired in parallel as I prefer to do, when shade knocks one panel out, the other panels are unaffected. So, even if 1/3 of one solar panel were shaded, reducing it to 0 amps of current production, the other three would be working just fine. The total current production would be 3/4 of what it could be if that one panel were in full sun (in this case, 21 amps), rather than 0 amps. The biggest problem to all this, is wire size! The more amps you pushing the larger gauge wire you need to supply the batteries.

I am no expert, but I have done a lot of reading over the last year. I've installed now two system, one in my 5th wheel, and one now in my Motorhome, I have discovered that more is better when it comes to solar panels. If I had the room, I would install 6 panels in a heart beat. Get the most you can afford is the answer to many questions on solar that no one likes to say, but it's true.

To go back for a second, you asked is 24v better than 12v - depends on your set up. But when you buy panels they usually come either 12v or 24v so make sure you know what you want. Other than that your controller is going to do the rest of the work. Ask Renogy for what you want but you have to know what you need, they don't.

if living off grid and I mean totally off grid like we do you can not live with out a 12 system. it is not a good idea to use a screw in led using a dc system. you are essentialy going from dc to ac back to dc. you would be better of to use a 12 volt led AND TAP into your 12 system for lights. it comes down to the amount of amp loss changing from one type of voltage to another twice.

Thanks, guys/gals,

I do understand the power loss by going from 12v-110v-12v and have a good number of 12v 'things' including of the 12v LED lights. The 40' shipping container is the second in line of three 40ft containers that I use for storing some of my wood and metal items that I use in the fab shop. I have those three containers wired up to one breaker in the shop and have a switch mounted at the first one and a receptacle so that if the power goes down for a while I can hook up a 10kw diesel (tractor motor) generator. They all are wired for 110v and currently have 110v LED lights in them. This 'sketch' is what I intend to use if the power is down for an extended period of time and/or if the house become unlivable. In one of the containers, I have just stored 600 gals. of off road diesel fuel with 12v transfer pumps and filters and diesel fuel treatment. I have (4) Renogy 100w 12v panels mounted on a swiveling, portable cart that will be stored in one of the containers for use in an emergency. I am doing this project to learn all that I can as I anticipate finally switching our house to solar. It's just the wife and I and our house is more like a cabin in the woods and is only 1400 square feet. It IS in amongst the trees , but the shop has a LARGE area that is way open to Southern exposure, but is about60 yards from the house. I have acquired several rolls of #4 gauge wire, assorted cable ends and terminal 'squeezer' to do the cables with.