4 405w panels vs 12 100w panels...

Tbleppy

New Member
Hello. I am in a little dilemma with setting up my solar. I initially bought 10 100w panels which i found out is a newbie mistake.
Woops. I set up a return for them with amazon because it was free returns and placed an order with a1solar for 4 405w panels instead.
Upon setting up the return for some reason it says ill get charged a return fee for 1 of the 2packs im returning. I have no idea how much a package that large will cost to ship! Then on top of that a1solar rejected my order saying cs failed. Called them, they cant give a reason. Said they dont get told why. Um, ok. Called my bank, an automation says its because my card needs to be registered to make an online purchase. Doesnt say how to register though. I click to speak with a person, it rings, then the ringing stops andno one is there. How come ive made online purchases without any problems with sites like amazon, ebay, sengoku without any hitch and then to order with a1solar now theres a problem?

Because of all this im now starting to wonder, is it even worth it? I could keep the panels i have now-10 100w 12v panels, add 2 more for 12 total. This will give me 1200 watts. My plan is to 4 string 3 panels each. Or to do 3 strings of 4 panels each.
These 100w panels have max parallel at 4 and max series at 12. It states that on their instructions although that is not mentioned on their web listing.
Specs for 100w panels are:
Pmax 100w
Max power voltage (Vmp) 18.78V
Max power current (Imp) 5.32A
Max system voltage 1000V DC
Open circuit voltage (Voc) 22.64V
Short circuit current (Isc) 5.7A

Specs for 405w panels are:
20.2% efficiency
49cents per watt
Voc 49.86
pmax 405w
Vmp 41.60
Voc 49.86
Isc 10.39
Imp 9.74
max series fuse 20A
max systm voltage 1000V/1500V DC

i have 4 LiFePO4 batteries 12v 100Ah:

i have a 40 amp cc but i have that set up for return.

My main goals are to power a fridge/freezer or maybe just a freezer(havent bought that appliance yet) and lights for a 2bdr home with 3 people. We are conservative on our energy use(been off grid for a while). Anything we get will be a step up from right now. Our system went down although im sure its fixable but I dont do that type of thing. We have a generator that runs our well pump and can run any urgent needs we may have. But im really in a hurry to try to get this system together. Obviously I want it to be right but time is of the essence. Im really new to this information. I think electricity is fascinating and Im happy to learn and like to. Right now I am seeking advice because I am feeling unsure how to proceed.

Has anybody wired 12 100 w panels together for a system? Is it worth it to do? Will I need a combiner box? I understand the series is negative to positive and parallel is positive to positive, neg to neg. For my particular set up I have a 5 ft wide deck that faces southward running the span of the house. After much thought, I think this is best location, reducing wire length substantially. So I would need the panels all in a straight row and I would tilt them, they would not be laying flat. Maybe a 30 degree angle. I am concerned about large amounts of rain or snow runoff on to them. This should probably be corrected with gutters. So i wont worry i suppose but there arent any right now.

How would I connect all these panels(12) in a row? Is that a huge hassle? Wasted effort? Need to forget that and pursue those 405watt panels still? It would be 4 of those. I think 2S2P with them. 1620watts. It sounds way better but as I said ordering them has been a hassle. Do i continue to pursue that because its so much better, or is what I have right now doable and adequate? I am thinking bird in the hand beats 2 in the bush.?. Any thoughts would be greatly appreciated. Thank you!
 

Hedges

Photon Sorcerer
The 12V panels say 1000V max system, so should be OK up to 40 panels in series, not 12.
I have 96, 12V 120W panels as 4 strings of 24 panels each.
The limit is max voltage of your charge controller, and Voc of the panel as adjusted for record cold in your location.

The larger panels would be more convenient. Less mounting hardware, and at 20% efficient more power in less space.

You can parallel two strings without fuses. More than that, should have fuses.
Since the 12V panels are 5A, can't have as many watts before you exceed two strings as you could with the 405W panels because they are 10A.
 

GXMnow

Solar Addict
There is nothing wrong with the 100 watt panels. They just cost a bit more per watt, and you need more of them. Since you already have them, you can make them work with the right charge controller(s). What are the specs on your charge controller besides being 40 amps? Are you going 12, 24, or 48 volts? What are you using for an inverter? Is this strictly off grid? Do you need auto transfer or gen start?

Using those panel spec, the 10 you have is not a bad setup. You should be able to run 2 strings of 5 in series with the right charge controller. 10 panels is 1000 watts. At 12 volts, that is 83 amps, going to 24 volts drops it to 42 amps, and 48 volts is down to 21 amps. For this size of system, the 24 volts looks like a good compromise. 5 panels in series calls for a max voltage of about 120 volts. Go with a 150 volt rated charge controller that can put out 50 amps at 24 volts. Then you need a battery bank that can take that power, and supply the loads you need overnight. Make sure your battery bank can handle 60 amps of charge current at 24 volts. (or 120 amps at 12 volts, or just 30 amps at 48 volts) 1,000 watts of solar panel could make about 5 KWHs in a day, depending on where you are, the time of year, and the weather. That can give you about 200 watts all day and night. That should run a smaller decent efficiency fridge. Good LED lighting is nothing. I found a 150 volt 60 amp rated unit for $250. That would allow you to go to 2 strings of up to 6 panels each for 1,200 watts. Or you could do 15 panels, 3 parallel rows of 5 in series. This particular charge controller has a 1,500 watt input limit at 24 volts, so that maxes it out. You can also use 2 smaller charge controllers.
 

chrisski

Solar Addict
For a 12 volt system with a 40 amp charge controller, You could do something like face six of these 10 panels to the south, 2 to the east, and two to the west. If they are set up 2 in parallel, you could run them to the same charge controller.

I get useful sun for one or two hours shortly after sunrise and shortly after sunset with something like this worth my portable panels for my RV By tilting them into the sun. My South facing flat roof panels do not get enough sun to start working until 9 to 10, and the panels I tilt and face the sun start producing around 8.
 

Tbleppy

New Member
Heres
There is nothing wrong with the 100 watt panels. They just cost a bit more per watt, and you need more of them. Since you already have them, you can make them work with the right charge controller(s). What are the specs on your charge controller besides being 40 amps? Are you going 12, 24, or 48 volts? What are you using for an inverter? Is this strictly off grid? Do you need auto transfer or gen start?

Using those panel spec, the 10 you have is not a bad setup. You should be able to run 2 strings of 5 in series with the right charge controller. 10 panels is 1000 watts. At 12 volts, that is 83 amps, going to 24 volts drops it to 42 amps, and 48 volts is down to 21 amps. For this size of system, the 24 volts looks like a good compromise. 5 panels in series calls for a max voltage of about 120 volts. Go with a 150 volt rated charge controller that can put out 50 amps at 24 volts. Then you need a battery bank that can take that power, and supply the loads you need overnight. Make sure your battery bank can handle 60 amps of charge current at 24 volts. (or 120 amps at 12 volts, or just 30 amps at 48 volts) 1,000 watts of solar panel could make about 5 KWHs in a day, depending on where you are, the time of year, and the weather. That can give you about 200 watts all day and night. That should run a smaller decent efficiency fridge. Good LED lighting is nothing. I found a 150 volt 60 amp rated unit for $250. That would allow you to go to 2 strings of up to 6 panels each for 1,200 watts. Or you could do 15 panels, 3 parallel rows of 5 in series. This particular charge controller has a 1,500 watt input limit at 24 volts, so that maxes it out. You can also use 2 smaller charge controllers.
Here's the panels I have:

I have 10 but think I will get another 2 pack to make 12. This way I can make 4 strings of 3 panels each.

I have this charge controller:

I have 4 of these batteries LiFePO4:

I have this inverter 24V 2000w:

I have this to charge the batteries with a generator if necessary:

I want to be able to power this freezer:

and this washing machine:

along with lighting. Ideally a well pump too but either way.

will this all work?
 

Tbleppy

New Member
Well pump is a tall order. You need to determine its running watts and especially starting watts (typically 5x running).
Then see if inverter could start it.
i dont know anything about the well pump to determine its running watts. It is a well at least 300 ft deep, the water travels at least 100ft uphill once it is pumped above surface. It currently runs by a 7000w 9000w peak generator. I can leave that as is because I know its not likely. But does the rest of the system configuration and loads minus the well pump sound like it works together? Do I have any shortcomings?
 

Hedges

Photon Sorcerer
With a clamp AC ammeter, you could get running watts for the pump. Starting watts will be 5x to 10x that.
Possibly can be reduced with a soft-start, which RV people use for air conditioners.

Other than that load, the selection of equipment looks OK.

12, 100W panels Open-Circuit Voltage (Voc): 22.64V
40A charge controller. Haven't found the max PV voltage spec.
Inverter 24V, 120VAC, 2000W. Says Surge: 3500 Watts, only 8 milliseconds so doesn't help. 400W rated motor x 5 = 2000W surge is largest.
Four, 12V 100 Ah LiFePO4, 100A discharge, 280A surge 5 seconds. 100A charge

If charge controller is 100V max, then 3s4p panels as you plan is good. Should have a fuse per string.
5.7A each, four strings in parallel is 22A. MC "Y" cables should work. Technically, need a connector rated for 22A x 1.56, but a 30A rated connector isn't likely to be a problem.

24V system x 40A = 1000W, at 28V 1160W. Good fit for 40A charge controller. You could add up to 50% PV panels if multiple orientations, without exceeding charge controller 40A capability.

Battery 2s2p, 24V 200 Ah. 40A charge is 0.2C, which I think is safer than 100A if you happen to use it in the cold. (their specs are probably for 25 degrees C)

4800 Wh battery.
Freezer is 75W. Would run for 2+ days off battery (DC)
Washer, 110VAC. Haven't found power draw, but wouldn't be much total. The 2000W inverter should be plenty.

Inverter no-load current 0.8A. Battery would run for a week with just that on.

120A maximum input, so fuse should be at least 150A. A class-T fuse and short 2/0 cables would be good.
Use 50A fuse for 40A charge controller.
 

Tbleppy

New Member
If charge controller is 100V max, then 3s4p panels as you plan is good
The charge controller is 100 V DC max. 4 strings of 3 panels each is 4s3p right? Is that a typo? Please clarify.

cables between solar panels and charge controller size would be 12awg? Battery specs say 6 awg battery cables to connect them together. Should i go with that? Then 2/0 cable from battery to inverter.?
Battery 2s2p, 24V 200 Ah. 40A charge is 0.2C, which I think is safer than 100A if you happen to use it in the cold. (their specs are probably for 25 degrees C)
can you please explain what 40a charge is 0.2C means?
 

chrisski

Solar Addict
cables between solar panels and charge controller size would be 12awg? Battery specs say 6 awg battery cables to connect them together. Should i go with that? Then 2/0 cable from battery to inverter.?
Really need to size wires based off ampacity, voltage loss, and heat rating.

I’d start by going to this calculator and plugging in distances.


In my case, for a 50 amps with no more than a 3% loss, a short run of a foot 6 AWG was adequate, but of several feet was 2 AWG.

With the 12 AWG wire, I don’t know the ampacity, but 10 AWG, wire types dependent, is around 30 amps. So with the wire I used, if the voltage calculator showed a small gauge wire didn’t have much voltage loss at say 14 gauge, if it was 30 amps, I needed at least 10 gauge.


For the inverter, I also looked at insulation rating. The amount of amps I was pushing showed a 90 degree C insulation rating for that wire, and if I pushed those amps consistently, the wire could get that hot. THat’s hot enough to burn someone. I decided on 60 degree C insulation, so for my inverter run, that came to 4/0. Please keep in mind that some ampacity charts or wire ratings will show 120 degrees C, which will boil water.

can you please explain what 40a charge is 0.2C means?
Basically your 200 AH battery bank charged at 20% its total rating. In my case, my FLA battery owner manual limitation is .13C which is the same as 13% of 458 amps or 1/8 of 458 amps, or 60 amps.
 

Tbleppy

New Member
Really need to size wires based off ampacity, voltage loss, and heat rating.

I’d start by going to this calculator and plugging in distances.


In my case, for a 50 amps with no more than a 3% loss, a short run of a foot 6 AWG was adequate, but of several feet was 2 AWG.

With the 12 AWG wire, I don’t know the ampacity, but 10 AWG, wire types dependent, is around 30 amps. So with the wire I used, if the voltage calculator showed a small gauge wire didn’t have much voltage loss at say 14 gauge, if it was 30 amps, I needed at least 10 gauge.


For the inverter, I also looked at insulation rating. The amount of amps I was pushing showed a 90 degree C insulation rating for that wire, and if I pushed those amps consistently, the wire could get that hot. THat’s hot enough to burn someone. I decided on 60 degree C insulation, so for my inverter run, that came to 4/0. Please keep in mind that some ampacity charts or wire ratings will show 120 degrees C, which will boil water.


Basically your 200 AH battery bank charged at 20% its total rating. In my case, my FLA battery owner manual limitation is .13C which is the same as 13% of 458 amps or 1/8 of 458 amps, or 60 amps.
will these connectors work:

id say the distance can be ten feet.

im calculating this at 40 amps. Im i correct to do so? I think i need 8awg from panel branch connectors to charge controller. Controller to battery ill use 8 awg again(thats the max the cc will take, but it is correct size per my calcs). Then at the batts ill use 6awg for a 2s 2p connection. From the batts to inverter ill use 2/0awg although i may want to bump it up to 4/0 awg so it will be cooler wires. At the inverter it is fine to use a heavy duty extension cord from there.

my estimated distances are 10ft panels to cc, 2ft cc to batts, 2ft batts to inverter. I could probably lessen it to 1foot if thats better to do.
 

Hedges

Photon Sorcerer
The charge controller is 100 V DC max. 4 strings of 3 panels each is 4s3p right? Is that a typo? Please clarify.

"Open circuit voltage (Voc) 22.64V"

4 panels in series is just over 90V at 25 degrees C.
The panel will have a temperature coefficient of voltage (found on data sheet) and consider record cold temperature for your location.
Unless your location is warmer than mine (San Jose), voltage will occasionally exceed 100V which could kill the SCC.

3 panels in series will always be a safe voltage.

cables between solar panels and charge controller size would be 12awg? Battery specs say 6 awg battery cables to connect them together. Should i go with that? Then 2/0 cable from battery to inverter.?

12 awg is fine for a single series string of panels or 2 strings in parallel (11A)

When fusing a PV array, fuse rating should be 1.56x Isc. This allows for actual current to exceed Isc by 25% for extra illumination from clouds, and then 25% margin to avoid nuisance trips. Wire needs to be a large enough gauge to have ampacity at least as high as the fuse.
You might have fuses for each individual PV string (probably 15A, could be 10A) and the combined wire still needs to be 1.56x Isc x number of parallel strings.

Battery wires should have a fuse 1.25x the highest continuous current your inverter or other load will draw. Wire gauge needs to have ampacity at least that much. It is possible 6 awg joining four 12V batteries as 2s2p for 24V would be good, and 2/0 to connect inverter. Depends on current draw.

Fridge/freezer probably has about 700W rating, but most of that is heater for defrost or ice maker. Compressor probably draws 200W to 300W continuous when operating, and 5x that or 1500W for less than a second when starting. Use the 1500W figure for wire resistance and IR drop calculations, also for inverter surge current (which it must sustain for a second, not just milliseconds). use the 700W figure for inverter continuous output. (or better, size wires for inverter continuous and surge capability in case other loads are added.)
 

chrisski

Solar Addict
will these connectors work:
I've got a couple comments on the MC4 branch connectors. Before I use these, since it is a set of three, I would but an inline MC4 fuse in for each string, perhaps $15 to $25 each. I said would, others will say must.

After that, how much amperage is going into the main MC4 connector to the SCC? The 10 AWG MC4 connectors I've seen are 30 amps max, so if this holds for the MC4 connectors you have, exceeding 30 amps after combined is a no go with MC4 connectors.
id say the distance can be ten feet.

im calculating this at 40 amps. Im i correct to do so?
For the run from the SCC to the battery or bus bar, then that would be what you plug in the voltage calculator. It will give you a loss you can expect at that AWG.. When I did mine, I measured for loss in 4 places. Solar panels to combiner, combiner to SCC, SCC to Busbar, and Bus Bar to Battery. My goal was 1% at each leg when practical, but I would accept slightly above 3%.

Others will tell you that's overkill, especially with the voltage loss for a 400 to 600 watt series of panels to a combiner box. So the method I said where I calculated the voltage loss, that ended up being plenty safe.

The one thing you mention is 6 AWG for batteries. I would not do that. I made my own cables with welding wire, and the battery cables are the same gauge as the battery to bus bar, and busbar to inverter. Perhaps you would be OK, but I included the three of four cables I have to wire my 2S2P battery bank in the distance I entered on the calculator.
 

Tbleppy

New Member
then 3s4p panels as you plan is good. Should have a fuse per string.
5.7A each, four strings in parallel is 22A. MC "Y" cables should work. Technically, need a connector rated for 22A x 1.56, but a 30A rated connector isn't likely to be a
please confirm, i will need 3 pairs of y branch connectors?
Or should i get the one with 4?
https://www.amazon.com/BougeRV-Connectors-Parallel-Adapter-Panel(1/dp/B07B4ZM8Y8/ref=pd_lutyp_crty_cxhsh_ao_3_1/138-5336663-1075664?_encoding=UTF8&pd_rd_i=B07B4ZM8Y8&pd_rd_r=e0291b30-5d31-4c92-826a-e2194466504f&pd_rd_w=xwdvv&pd_rd_wg=80G1M&pf_rd_p=4dfead9f-30ab-48ab-9e02-5cc3fb060b27&pf_rd_r=WRV5KMBFD11VF7AT06VT&refRID=WRV5KMBFD11VF7AT06VT&th=1
is this diagram accurate?
20210223_211703.jpg
22 x 1.56 is 34.32 so the wiring calculations should be rounded up to 40amps? Or not. Round to 35? Probably. Im giving myself 10 feet of length from the y branch connector to cc. It could likely be less but not likely more.

Result​

Voltage drop: 0.44
Voltage drop percentage: 0.37%
Voltage at the end: 119.56
Getting this from the voltage drop calculator when i input 10 ft distance at 35a. I put one set of conductors, is that right? Im putting DC as phase since it is running from panels to cc. I am putting 8awg since thats the max my cc will receive and im putting copper. Did I use this correctly and how do i decipher the results please? After the cc im presuming will have to be 8awg again because thats what the cc accepts max thickness, to the battaery bank. Im estimating that distance as 2ft. Is that a good distance? Then the battery cables i am told should be 6awg by battery manufacturer. Should i blindly go with that number or would i possibly benefit at a different size? Presuming 1 ft for battery connection distance 2s2p. Batteries to 24v inverter. That amp number would be based off my loads right? That was a good breakdown already but with the 2/0 will that be hot wires, 90 or 120 degrees? Or will it be 60 degree wire?
Thank you!
 

Tbleppy

New Member
fusing a PV array, fuse rating should be 1.56x Isc. This allows for actual current to exceed Isc by 25% for extra illumination from clouds, and then 25% margin to avoid nuisance trips. Wire needs to be a large enough gauge to have ampacity at least as high as the fuse.
You might have fuses for each individual PV string (probably 15A, could be 10A) and the combined wire still needs to be 1.56x Isc x number of parallel strings
5.7 is Imp. Multiply by 4 in parallel is 22.8A x 1.56 is ~36A. Size the wire to 36A which is 8awg. Should i do a 15a or 10a fuse per string? How do I install a fuse?
 

Tbleppy

New Member
AWG.. When I did mine, I measured for loss in 4 places. Solar panels to combiner, combiner to SCC, SCC to Busbar, and Bus Bar to Battery. My goal was 1% at each leg when practical, but I would accept slightly above 3%.
are you referring to a combiner box or y branch connectors? Do i need a bus bar? What is that?
 

Hedges

Photon Sorcerer
Either 3 pairs "Y" or one pair of 4:1 would work.
You may need a few short cables to make things reach, can attempt to sketch out.

Rather than 3 "Y" at the same level as you've sketched (with probably ore connections than can be made,

Two "Y" plug into one "Y" to make 4:1

Two panels join with "Y" as a parallel pair. Two more panels join with "Y" as a parallel pair. Those two pairs join with third "Y" as 4:1

You should also get MC fuse holders, and fuses of the value shown on panel label.

If you use "Y" cables, then no need for combiner box, just run MC cables back to charge controller.

Alternate to "Y" cables is a box with metal bar to connect several cables (like neutral or ground bar in breaker panel). Typically also has fuse holders or breakers for positive.
 

chrisski

Solar Addict
are you referring to a combiner box or y branch connectors?
Combiner and Y Branch connectors do the same thing.

I have two panels on my roof that are connected with the Y Cable, each panel which has an in line fuse at the Y connector. Advantage is easy to build and can be placed on the roof And a little cheaper.

I have two more strings of panels, three each series for 3S2P where each string is run down to my battery compartment to a combiner. This is an electrical box that combines the strings of panels and has a place for a circuit breaker instead of a fuse. If I’m working on my system and need to shut the power off, these circuit breakers make it a breeze to remove power from the SCC. A disadvantage is although designed to go outside, these are for the vertical position only, and for my RV build, could not be put on the roof. https://www.amazon.com/Midnite-Sola...14166238&sprefix=Mid+nite+sola,aps,368&sr=8-3

Do i need a bus bar? What is that?

I would think you need a bus bar. This is where I combine seven units and outputs to my system. I have three SCCs, one battery bank, one inverter, one RV DC power, one auxiliary DC power each with their own post on the bus bar. I recommend a covered bus bar. The Busbar will need to handle the amperage of your system. I stayed away from the stereo busbars that were rated for high amps, and went with a one designed for DC electricity usage. They’re bigger than you think with 3/8” posts. I need one for the + side and one for the - side, and my 8 post 3/8” busbar is 12” long, and there’s two of those.

THis is different than I have, but I like this better because it has 4 big studs, and some smaller ones. Not all my studs needed to be 3/8”. They’re available in many, many sizes.

 

Hedges

Photon Sorcerer

chrisski

Solar Addict
An observation ... that busbar costs more than his charge controller. Over 25% of his inverter.
Just for a piece of metal.
For me I want my busbar to be rated for above my max amperage. 600 amps and 1000 amps is quite high. There are plenty of options. Done over again, I'd get a Blue Sea products with two 3/8 terminals one for the inverter and other for the battery, and the rest could be screw sized terminals with covers.

What's your thoughts on using a 250 amp audio busbar vs a 250 amp blue sea bus bar?
 
Top