12v/24/48v parallel or series? Confused!!

[Brandon8791]

This is basically an overview of everything.I'm getting x2

then 1 separate panel with another controller, and then the 200 watt mono panel pictured above in last reply

also I might add that I don't mind one bit to upgrade the inverter or controller, lol I just bought the kits and such cuz I knew it was a great price, especially for the panels. So any insight on that is great.

and I'd also like to add that I definitely appreciate the information and I've been researching this literally for.hours a day and watching videos trying to.make sure I understand.this fully before everything gets here (2-5 weeks) it's all coming from China air mail so it'll take some time.

hopefully I have provided adequate information to help you guys.understand.and not only that but help me understand the series/parallel and what.needs to go where I guess, I'm guessing I have to separate so many panels to different controllers...

I think I'm understanding it as like 6-8 panels in series goes into one controller and that goes into one set of batteries set up in series for 24v? Then another 6-8 panels into another controlled and another battery bank? And just keep it all separate am I understanding that correctly? If not feel free to correct me!

[Brandon8791]

Ah ok, so you basically don't wire all the panels together you have to separate them into different sets? (Or ig strings) like 1 set of 6 panels, another set of 6 panels? I'm basically getting 13 windynation 100 watt polycrystalline panels, and one 200 watt macht monocrystalline panel to total a 1.5kwhile system. The reason it's different is because I won all this on auction with 2 1500 watt modified sine wave inverters, 2 p30l battery controllers and 2 50 foot mc4 connector extensions with bare wire on the ends to connect to the controller... I won all this stuff for like $785 so I thought it was a fair price and would get me somewhere.

[Mike90250]

OK, I've surfed to find you a couple pictorial examples. I in no way able to explain Series and Parallel circuits. There are many basic electricity sites that already do that,

The limits you need to set are

1) ARRAY VOLTAGE.
If you are using a 24V inverter, then you don't want to wire your panels to more than 100V The higher voltages push the MPPT controller into less efficient operating ranges as it downconverts your array voltage to battery voltage. (if a 12V inverter system 75V is the highest you should design for)

2) PARALLEL PV Strings need fuses
More than 2 parallel strings need a fuse on each string

Ideal, if you could stay at 2 parallel strings (5 series panels ea) without overvolt on the controller. there will be a sticker on the back of the panel and we will need these values to completely spec this out,

sample:
Vmp = 18V
Voc = 22v
Isc = 5
Imp =4.5
Series fuse = 7A
The Voc is the value used to determine controller overvoltage So a Classic 150 could have up to 6 of these <sample> panels in series. 7 will kill it @ 154V

sample pics parallel-series-circuit-x16.jpg

[Brandon8791]

Hmmm.... well now I've looked up the enphase inverters but I don't think that would work with a battery back up lol guess u can't have best of.both world's on that either >.>

[Brandon8791]

So I'm confused do my panels need to be parallel or series to charge a 24v battery bank, lol see I'm getting confused on what's happening. Or do I need to just stick with a 12v panels and do 12v battery bank? My panels.I believe are all going to be 12v or 18v max I think, but if I did them.in parallel the voltage would stay 12v which wouldn't charge a 24v system I thought, so it'd have to be series. And if I did series then I thought the mppt controller is a lot more efficient and it's a lot more efficient with the solar panels as well cuz it basically multiplies to voltage which means less watts and amps is wasted. Like say the sun just came up each panel is producing 4 volts, in parallel that's not enough to charge a 12v battery bank, but in series with say 4 panels, that's 16 volts Which will charge the system. So nothing is thrown away.


so are u saying I'd have to create a separate system every 3kw? To stay under the 150 volts inputed to the MPPT? or how do I do parallel but keep the voltage up lol like I said I am so confused it's unreal but I want the most efficient system I told myself that if I'm going to do this then I'm going to do it right

[inetdog]

And now I've looked up these MPPT controllers and finding a lot of them only accept up to 150 and 200 volts? Well even if u did 13x250watt panels you could only have a 3250 watt system. 13x12v would be 156 volts which is right at the max. So how do you find.ones that can handle say 400 to 600 volt input? I'd probably need a decent sized system to be off grid so I'd need a pretty big MPPT controller, or do you.need 2 separate ones or? Lol thats if I'm even understanding this series thing correctly and if it's even the best route to go?

You don't try to find high input voltage, you put more strings of the same length in parallel to work with the size controller you have.

Once you get beyond 100V or so on the panel side there is less benefit to be gained from making the wires smaller.
If the two strings are going to have different shading or temperature conditions, then each string would need to go into its own MPPT input.

[Brandon8791]

And now I've looked up these MPPT controllers and finding a lot of them only accept up to 150 and 200 volts? Well even if u did 13x250watt panels you could only have a 3250 watt system. 13x12v would be 156 volts which is right at the max. So how do you find.ones that can handle say 400 to 600 volt input? I'd probably need a decent sized system to be off grid so I'd need a pretty big MPPT controller, or do you.need 2 separate ones or? Lol thats if I'm even understanding this series thing correctly and if it's even the best route to go?

[Brandon8791]

Yeah I've tried to do a lot of research on this and I kept getting directed to this forum so I was like we'll Ill just make an account here and ask the folks the specific question I have since I couldn't really find a direct answer... so basically if u get a mppt controller it doesn't matter if u hook up say 13 12v panels in series which in turn would create 156 volts. It would bring it down to 24v to charge say a 24v battery bank or something? I'm trying to do a grid tie system but have a battery back up to power the house when the power goes out or slowly work my way off grid.

would the mppt controller use the rest of the watts and amps? Or the other say 122 volts that the series panels produce? Lol hopefully you all don't get mad at my stupidity!

[inetdog]

The common battery bank voltages for which equipment is produced and sold in large quantity are 12, 24, (36) and 48.
Most do not go above 48 since it puts their installation into a different safety category under the National Electrical Code (NEC).
36 is common for golf carts but not for PV systems.
The higher the voltage the lower the current for the same power and the less money you have to spend for larger copper or aluminum wires.

On the panel side, you can take two nominal 12V panels and put them in series to charge a 24V battery through a PMW (inexpensive, different design) CC.
If you use a more expensive and efficient MPPT type CC you can work with a panel string voltage that is much higher than the battery voltage and still make use of all of the available panel power.

You can get a lot of this information and more by reading the sticky threads in the Off Grid topic area of the Forum.

[Brandon8791]

OK I've looked this up several times and it really is confusing lol. I understand parallel, I understand series. What I don't really understand is how u keep series from going above 24v? I think what I've been looking up is its best to do 24v battery back up and a total system rather than a 12v battery back up and system for a house... is that correct.

I am about to have a 1.5kw system arriving at the house in a few weeks, 13 100 watt panels and a 200 watt panel. (I won it all on bid on ebay for like $700 with 2 invertors and 2 battery controllers, cables, mc4 connectors and all to do the system. I know it goes from the panels to the controller to the batteries and then the inverter... or I think

but again I get confused with what's best? I think 24v is but when you hook two 12v panels together u get 24v in series, so If I connected another in series would that bring it to 36v? If I did a 24v battery bank which I thought was preferable wouldn't 36v be bad? I know the wattage isn't going to change but I'm so confused on how to maintain a solid 24v? Do you just keep hooking two panels in series to 24v and do that every 2 panels or what? Lol I am probably making this a lot harder than I think but maybe you all can help!! Thanks guys