Just Purchased Panels Now looking to get additional equipment

[rashamon12]

Ok so i just bought 8 Renorgy RNG-320D 24v panels which i will be using for a schoolie build that will prolly be transferred over to a small home in the future. I was thinking of making this a 24 volt system.
These are the other parts i was thinking of getting though i have no idea what charge controller to use tho i was thinking of going with a victron controller. the table i have here is my solar panels specs. I am new to this though i do have a little electrical experience but so much to wrap my head around it need some additional help

-Victron MultiPlus 24/3000/70-50 120V VE.Bus inverter charger
-Victron Orion 24/12V-70A Converter for step down to any 12v items
-unknown charge controller was thinking also victron but don't know which one or optimal wiring for panels
-Crown CR430, 6V Flooded L16 Battery 430 amp hr (configured for 24 and for 2560w of panels)

Max Power at STC: 320W	Open Circuit Voltage: 40.1V
Short Circuit Current: 10.08A	Opitmum Operating Voltage: 33.7V
Optimum Operating Current: 9.50A	Operating Temperature: -40°F to 194°F (-40°Cto 90°C)
Dimensions: 65.6*39.5*1.4 in (1666*1002*35 mm)	Weight: 40.8 lbs (18.5kg)
Solar Cells: 60 Monocrystalline	Cables:12 AWG (2.95 ft)
Junction Box: IP67	Connectors: solar connector
Module Efficiency: 19.18%	Maximum System Voltage: 1000VDC UL
Maximum Series Fuse Rating: 15A

[Mulley]

Hi Rashamon12, I am new to this and another DIY. Here is the specks on the back of my panels. I just made a word file of them.

Rated Power: 270W

• Open circuit voltage (VOC): 44.4 V
• Max power voltage (VMP): 35.5 V
• Short circuit current (ISC): 8.25 A
• Max power current: 7.60 A
• Power Tolerance 0/+3%
• Maximum system voltage: 600V (UL)
• Fuse Rating: 15 amp
• 20 used panel and a battery pack Lithium, 200ah at 48 volts.

Now about yours, I see you have "Maximum System Voltage: 1000VDC UL." This I am assuming is how many solar panels you can arrange is series. That would be about 25 panels. 1000/40.1=24.9. OK you only have 8 panels and no solar charger at the moment. That is my problem also. Solar chargers are like women they are not all the same. I have my panels are arranged right now 10S-2P. I have the panels mounted and wired 10S-2P. OK? Do you understand the notation? I have 2 positive and 2 negative PV wires from the array. I have been monitoring the open voltage of each set of 10 in series and in a cold morning with good sunshine I read 418 open voltage. This is a problem I need a solar charger rated at least 500 volts and about 5500 watts. I have found some but they are costly. You have the same problem depending upon how you connect your panels. If your array is 4S-2P you will need an solar charger that will handle 40.1x4=160.4 open circuit volts and 8x320=2560 watts. Me I do have to get back up on the shop and connect the panels differently. Next array I do will be ground base then this old man can just stand up and rewire. I have not found much help so far. Mulley

[Droo71]

I am using 12 panels; I don't remember the exact Vmp or Isc specs on mine, but including cold temperatures for voltage, and summer sun for amperage I ran my 24V/300W panels in 3 strings of 4 each.

This means I have 3 strings, each one has 4 panels in series. I am taking these strings to a combiner box - you *need* to get combiner boxes. I am using a Midnite SOlar MNPV6-250, but there a lot of options, depending on your install. Where I am located, I don't need rapid shutdown for a ground mount, so the MNPV6 works well for me.

Now - some considerations. My strings each hit a 15A breaker in the combiner box. With 4 in series, my max voltage at -40C coudl get up to 180V. This means I had to use 300V breakers -- essentially 2 150v breakers in series - so I only have 3 strings in my combiner box. It also means I need an MPPT controller good up to 200V.

If I was doing it over, I would use 4 strings of 3 panels. This would still need 15A breakers, but i could put 4 strings in with 150V breakers, which are cheaper, and use a Midnite Solar Classic150 .

with 8 panels -- you are either going to need 2 strings of 4 -- which is going to require 300V breakers/fuses at your combiner, or 4 strings of 2 -- which is no problem for voltage, probably a little better efficiency going through the controller as the voltages between your input/output on the controller are closer together - but will basically fill a combiner box. I might consider getting a 9th panel and using 3 strings of 3 panels each.

Midnite has a sizing tool for their charge controllers here:

https://www.midnitesolar.com/sizingTool/index.php

I don't know if Victron has one - I suspect they probably do. Magnum has one for their PT-100 (which I use, because it is good to 200V/100Amps).

Those maximum system voltages of 1000V are fine for large commercial installs - that's 20 panels at 24v with a decent safety margin -- but I don't think they generally translate well to a small school or a standard residential install.

[Mulley]

Hi rashamon12, In the post of Droo71 I am very confused. He has 12 panels 24V/300W connected 4S-3P, at least that is what it seems like I could be wrong. So if they were connect 4S-3P each string of four 24volt panels has an (open voltage) of 96 volts. I am very confused as he has 180 volts.
PV in series adds volts (watts stays the some) PV in parallel adds watts (volts stays the same). Maybe it is a typo and his panels are around 45 volts VOC.

If a solar array had a 1000 volt limit and you used only 20 panels which were 24 open circuit voltage then 20x24=480 volts which is quite a safety margin. My array is reading 418 volts on a cold morning which is scaring me and I have to go up on the shop and connect a bunch in parallel. Mulley

[Droo71]

Hi rashamon12, In the post of Droo71 I am very confused. He has 12 panels 24V/300W connected 4S-3P, at least that is what it seems like I could be wrong. So if they were connect 4S-3P each string of four 24volt panels has an (open voltage) of 96 volts. I am very confused as he has 180 volts.
PV in series adds volts (watts stays the some) PV in parallel adds watts (volts stays the same). Maybe it is a typo and his panels are around 45 volts VOC.

If a solar array had a 1000 volt limit and you used only 20 panels which were 24 open circuit voltage then 20x24=480 volts which is quite a safety margin. My array is reading 418 volts on a cold morning which is scaring me and I have to go up on the shop and connect a bunch in parallel. Mulley

Mulley,

24V is the 'nominal' voltage. I have a CS6K-300MS panel, 24V, 300 watts.

The actual *operating* voltage of the panel is 32.5V ,
The open (short circuit) voltage is 39.9V .
4 x 39.9 is 159.6V on 4 panels. You need to account for this voltage for both fuses/breakers, and MPPT.

Then, you need to allow for 'cold'. Where I am, I need to allow for a voltage increase due to cold temperatures down to -30 , using the temperature coefficient (this is different for every panel) of -0.29 % / °C .

So with a safety margin - I need to plan for ~180V .
You can see the specs for my panels here:

https://d140hlzzaoq16w.cloudfront.net/media/sparsh/product_attachment/custom/upload/Canadian-Solar-SuperPower-CS6K-MS-datasheet-eng.pdf

20 panels at 24 volts nominal looks like 480 V. But the short-circuit voltage on my 24V panels would give you 957 volts. (24*39.9) .. you need to look at the Vmp (max power) and Voc (open circuit) numbers to calculate this safely.

Look at the datasheet. If you go to the Midnite calculator I provided, you will see the sheet asks for these Vmp and Voc numbers in order to calculate safe voltages.

PV in series : 4 panels in series, 300W each , nominal 24V (actual 32.5) is 1200W (watts add) at 96 volts nominal, 130 volts actual operating volts, over 160Volts in a short-circuit. Your safety planning has to be short circuit. This is all at 9.2 amps. *VOLTS* add in series. (1200W/130 = 9.23, 300/32.5 = 9.23 .. 9.23 Amps)

PV in parallel : 4 panels in parallel, 300W each, nominal 24V (actual still 32.5) is 1200W (watts still add) at 24 volts nominal - 32.5 volts actual operating, about 40V in a short circuit. (1200W/32.5V =36.9A) This will be at 37 amps, because watts are the same, voltage is lower. AMPS add in parallel. Amps * volts = Watts. Watts don't change.

Please don't use the 24V value for your calculations. You need to look at the actual operating values for your expected results from the panels, and you need to look at the open (short) circuit values for your safety calculations -- and then you need to know that as it gets colder, voltage goes up, so you need to count that too (depending on how cold it gets where you are).

[Droo71]

Mulley, your Voc is 44.4V, I see.

If it gets cold - lets say to 0 Celsius, you need to take your temperature coefficient and multiply it by 'how far below 25C'. So if your coefficient is the same as mine of -0.29 -- then you get 7.25 (-25 * -0.29)
You need to add that 7.25 'temperature' volts to the Voc - that would give you 51.65 maximum volts for a short circuit. 42.75V for normal operating maximum. That will put you over the 500V for the maximum system if you have a short.
I don't know your panels or what your temperature coefficient is, but it needs to be counted for maximum system voltages as well.

I still suggest for school, residential purposes - with 24v panels, not more than 4 in series, and find a 200V charge controller, like magnum or midnite. 150V is simpler if yuo can manage, although with 24V panels, that means only 3 in series, and use combiner boxes to run it at higher amperages.

[Mulley]

Hi Droo71, Thank you for the reply. I see now that I am not compensating enough for temperature. I have the panels on the roof of my shop at 10S-2P and they are connected but no combiner box yet. I have checked the VOC of the 10S panels at 418volts which I now see is too much. I do appreciate your comments as I am just learning. The reason I was wanting a higher voltage system is that it is 100 feet to my house from the shop. I am not sure how to proceed yet. I see a lot of hybrid inverters/ chargers but do not trust the cheap ones. So I will try to find an mppt charger at 150 volt rewire the panels get a combiner box with fuses (whatever). I am thinking just use 10 panels maybe 2S-5P and leave the other 10 in series and check the voltage all winter as they are and then next summer see if I can arrange a higher voltage system. Thank you: Mulley

Rated Power: 270W

• Open circuit voltage (VOC): 44.4 V
• Max power voltage (VMP): 35.5 V
• Short circuit current (ISC): 8.25 A
• Max power current: 7.60 A
• Power Tolerance 0/+3%
• Maximum system voltage: 600V (UL)
• Fuse Rating: 15 amp
• 20 used panel and a battery pack Lithium, 200ah at 48 volts.

[Mike90250]

Midnight Solar https://www.midnitesolar.com/product...20-%20Classics
Morningstar https://www.morningstarcorp.com/prod...tar-mppt-600v/
Schneider 80A & 100A version https://solar.schneider-electric.com...-controller-2/
at only 200VDC solar input Magnum https://www.magnum-dimensions.com/pt...rge-controller
all have > 150V controllers.
Quality is not free.. Figure the cost difference of a world class controller, vs extra combiners, larger wires and see what makes sense for you. There is no one size fits all

[chrisski]

What is it you need a 70 amps at 12 volts? Somethings a smaller charger controller with a 12 volt battery would be good, and others a 70 amp converter will be fine.

[Mulley]

I think I should start a different thread for my problems. This one is for rashamon12 . Mulley

[rashamon12]

lol i dont really mind too much seeing as every example i get helps me understand more but i am just trying to get an optimal setup and dont want to invest and then regret it. I want to be able to grow the system if need be thus y i went with vicktron as my primary choice for parts i am thinking of getting. not sure if i want to do 2 strings of 4 or 4 strings of 2. i want to minimize loss but also dont want to have to go way overboard.i was debating getting 2 charge controllers so that i can grow the system more easily but again not sure if thats the better option. i do want to also be able to run higher demand things off of it seeing as i have a mothership gaming pc (1000w power supply in it but pulls between 600 and 700w) id rathar buy once and cry once when it comes to the solar setup unless its just adding more panels and or batteries. I do plan on going lead acid because i have anything i would ever need to restore and maintain lead acid batteries as well as a vast amount of knowlage about them since my father was a chemist who worked in a lab designing and improving modern lead acid batteries.

[Droo71]

Strings of 4 are generally manageable as long as you are within voltage spec for your charge controller. Find your panel specs and go to the Midnite or Magnum charge controller calculators to find your votages.

Some of the charge controllers - LVictron sells some -- can be stacked, so you can always add to what you have without throwing away money... if you find you have more panel/power input that your charge controller is able to push, just stack in another charge controller.

[rashamon12]

all the calculators i have looked at including the one above asks for specs that the solar panels are not showing on them. i also linked the specs above in my first post thats whats in the pdf of the specs.

[Droo71]

All your specs are here:

https://www.renogy.com/content/RNG-320D/320D-Datasheet.pdf

Here's the numbers you need. I don't know if Victron has a sizing calculator - but you CAN use the voltage and current numbers from the Midnite calculator to compare against victron specs.

Watts : 320
Voc: 40.1
Vmp: 33.7
Isc : 10.08
Imp: 9.5A
Temperature coefficient for Voc : -0.33%
Temperature coefficient for Vmp: -0.47%

When I plug that into the Midnite sizing calculator for 2 strings, 4 panels a string, I get a VoC of 160.4 volts, and a VoC at -30C of 189.6 volts -- it would require a Midnite Classic200. WIth 4 strings of 2, all 3 sizes work.

[rashamon12]

thank you droo for that information. now i just need to decide the best brand of controller and the best feature set for the controllers. I think i will do 2 controllers so 2 strings of 4. i would be interested to hear from everyon what charge controllers they use and their experiences with them along with the strengths and weakensses found. the more information i can get will hopefully lead to the correct decision for me. It is much appriciated btw so everyone thanks and hopefully this info helps others as well