12 panels 405w each

abdallah.91

New Member
Hello everybody I am something confused about the max power that should be taken from 4860w panels (12 * 405w and each 3 panels are in serie so 4 string). these panels feed the MUST PH18-5048 Plus inverter throught 8mm square copper cable. the maximum power that I have taken during sunny day between 11AM and 13,00 is 3200W from the solar to the load directly without the battery help,. any more load the battery will help. is it what I should expect from 5 KW system?? I am not convinced. if it is under performance what the possible reasons are?

Regards
 

FilterGuy

What, me worry?
Panels are all rated at the same Standard Test Conditions (STC). This makes it a little easier to compare panels but these are ideal conditions that are rarely met in real life. Consequently, it is somewhat unusual for panels to actually produce as much as they are rated for. However, 3200 W for 4860 (35% loss) does seem low.

There can be multiple factors:

Edit: Changed MPPT to PWM below
* Positioning is important. The panels will produce the most when the sun is hitting them straight on. If they are angled to the sun, production will be less.
* Even a little shading can pull down the output of the panels a lot.
* Heat can also significantly reduce production. If the panels are not mounted with plenty of ventilation around them, production can be impacted. particularly on hot days.
* A long run from the panels to the inverter can reduce the production if the cables are not over-sized to minimize voltage drop. (Your configuration is probably running ~40A at peak production. That will require 8AWG even for a short run.)
* What are the specs of the MUST PH18-5048 Plus charge controller? If it is rated for less than 4860W....it will throttle production back to what it can handle (assuming the voltage is not over what it can handle.... then it would just burn out)
* Is the MUST PH18-5048 Plus charge controller an MPPT or a PWM? Most All-in-ones have MPPT controllers but I have seen specs for some that have PWM controllers. The configuration of those panels probably is driving 120V at the controller input. That would be way too high for the sweet spot of an MPPT controller for a 48V battery (I am assuming 48V based on the model number)
* There can be significant output differences between good and bad solar controllers. Some just do a better job of harvesting the energy than others. I know nothing about the MUST PH18-5048 Plus converter but if it does not have a good MPPT controller, your production will suffer.
* Of course, if the battery is full and not taking current, the production will drop.... but that does not sound like what you are seeing.

One more thing: 405W is a big panel. Are they Bi-facial? If so they need to be mounted in a way that maximizes the light that strikes the back of the panel as well as the front.

Also note that all of the issues above are additive. If your panels are a little off angle, a little hot and have a little shading, the result could be a big reduction in production.
 

abdallah.91

New Member
Hello and thanks a lot for your declaration. I hope I can feed all the information that you asked about.
first thing i will attach a screenshot of the Must PH18-5048 Plus specification. it is a hybrid MPPT charge controller. see attached the specifications.
I am living in Lebanon, the best vertical angle here is 35 degres, so I designed and built a very tall mounting bracket that 100% 35 degrees inclination. and absolutely nothing could shading or facing any part of the panels.
depending to the cable it is arround 35 meter from panelscto the inverter, it was was 4 mm2 DC cable (red-black) recently I replaced it with very thick copper cable maybe triple the thickness so it is pure copper that is thicker that the pencil(around 8mm copper diameter).
the Must inverter is 5000 kw but its max input PV power is 4000w, so I isntalled panels more than its ability.
the max VOC that inverter could accept is 145V DC, rhe panel VOC rated is 50.5V but I never measured more tha 46V so the string open circuit voltage is 136V at maximum. maybe it is better for the MPPT to reduce Vmp voltage so put 2 panels in a string instead of 3?

currently I still waiting for the 48v 200A Lifepo4 battery to arrive from China, so I am using old used 12v car batteries with different sizes at least to benefit from the day light power until the good battery arrives.
please see also the mounting brackets and installation.
 

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FilterGuy

What, me worry?
Panels:
Vmp =41.4V
Imp = 9.79A
Voc = 50.8V
Isc = 10.23A

Controller
1632463658310.png

With 3 in series the String Vmpp voltage is 41.4 x 3 = 124.2. However, the total Voc is 50.8x3=152.4V THAT IS TOO HIGH FOR THE CHARGE CONTROLLER. The charge controller limit is 145V and its optimal operating range is 60V-130V. I recommend you disconnect the panels immediately. The lack of production may be due to this so there is no sense in trying to figure anything else until this is fixed.

Those panels should be run wit a max of 2 in series for that controller. That will give a string Voc of 2 x 50.8 = 101.6V. It probably does not matter in Lebanon, but that also gives plenty of buffer in the Voc to handle extreme cold conditions.

Since there are 12 panels, configure it as 6 strings of two in series. That means an Isc of 6 x 10.23A=61.38A and a working current of Impp=9.79A x 6 = 58.74A.

Here in the US, the standard safety margin for solar current is 1.55 x Isc. So that would be 61.38*1.55=91.04A Therefor the minimum cable size for a US install is 4AWG. With the 70M round trip to the inverter and back, that needs to be increased to 2AWG to keep the voltage drop below 3%

This is what I get when I plug 2AWG into an on-line conversion tool:


1632463853777.png


8mm diameter copper should be OK.

Once things are reconfigured, let us know what kind of power the system generates.
 

abdallah.91

New Member
Thanks a lot,

So the first thing I am going to do is to re-arrange or rewire the panels, 6 strings of 2 in series.
just a modest question, why we are comparing the VOC or 3 in series (152.4V) to the PV array MPPT voltage (64-130V) not to the maximum PV array open circuit voltage which is 145V?

Regards,

Abdallah
 

FilterGuy

What, me worry?
When the batteries are full, the MPPT controller will turn off the current from the panels. From the panel's point of view, this looks like an open circuit....so Voc is used to calculate max voltage.

In my comments, I *was* comparing the string Voc to the max voltage of the controller.
However, the total Voc is 50.8x3=152.4V THAT IS TOO HIGH FOR THE CHARGE CONTROLLER. The charge controller limit is 145V and its optimal operating range is 60V-130V.
Perhaps I confused things by commenting on the operating range in the last part of the sentence.

The operating voltage is 3 x 41.4 = 124.4 and that is in the optimal operating range of 60V-130V. Consequently, there is a possibility the string voltage is not contributing to your power loss. However, since the array needs to be reconfigured anyway, it is best to wait till we have that done and we know the new power generation before we go any further.

the max VOC that inverter could accept is 145V DC, rhe panel VOC rated is 50.5V but I never measured more tha 46V so the string open circuit voltage is 136V at maximum.
The statement should read "...so the string open circuit voltage is 136V at maximum, for the conditions it was measured under." Using a measured Voc is, in my opinion, too risky (Other people may disagree). There are several physical conditions (like temperature) that change the Voc at time of measurement but may be different at other times.
 

Roqm

Solar Enthusiast
Also always consider the voc as was mentioned a weird or freak cold in your area would put voltage to high for your equipment..better to be safe now than sorry later.
 

abdallah.91

New Member
Hello again,

I did what you have suggested, I finished reconnecting the panels in string of twos in series at 11.00 AM. between 12, 30 PM and 13,00. the figure below was the status of the inverter. I turned on 2 water heater (1200 Watts each) + 1 heater (800 Watt) and 3 refrigerators and a 60 Watt fan. I think now it is better. can I said that this is the peak power? I forgot to mention that today was very sunny without any clouds in the sky. also I checked each panels short current circuits, they was between 9 and 9.5 Ampers using clamp meter.
an important thing I should mention also is that the (6 mm square cable as I estimated it) got very heated so I put the 4mm DC cable in parallel with, the current divided arround 50 Ampers in the thick cable and around 25 Amp in the thin cable.
whst do you suggest now?

thanks a lot for your help.
 

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FilterGuy

What, me worry?
If I follow everything, you are getting ~78.6% of the rated power of your panels. That is better but not quite as much as I would expect.
the current divided around 50 Amperes in the thick cable and around 25 Amp in the thin cable.
That is a total of 75 amps which is much higher than I expected. Do you know what the voltage is at the combiner box? Also, What is the ambient temperature?
 

Usangira

New Member
Hi
I think I am suffering from the same problem. I have 5Kw PV array in sunny Dar es Salaam which is giving me hardly 2700watts during peak and a maximum of 14kwh per day
10pcs of 500W in 2S5P setup.
My charge controller is 100A, 150V
My 12AWG running cable is only 30m
I am desperately looking for ideas to crack this out
Thanks, Innocent
 

Sanwizard

Photon Sorcerer
Hello all,
any comment it will be helpful so I appreciate it, please help me.

Regards
Looks to me like you may be getting voltage drop on your wiring. Is it just me, or do the smaller gauge wires in your combiner box look discolored from heat?
Try using a busbar instead, and see what happens.
 

FilterGuy

What, me worry?
Hi
I think I am suffering from the same problem. I have 5Kw PV array in sunny Dar es Salaam which is giving me hardly 2700watts during peak and a maximum of 14kwh per day
10pcs of 500W in 2S5P setup.
My charge controller is 100A, 150V
My 12AWG running cable is only 30m
I am desperately looking for ideas to crack this out
Thanks, Innocent
We need a lot more info to give you any advice.

Isc and Imp of the panels
Voc and Vmp of the panels
Voltage of your battery
 

Usangira

New Member
We need a lot more info to give you any advice.

Isc and Imp of the panels
Voc and Vmp of the panels
Voltage of your battery
My Battery is LiFePO4 48V, 400Ah hooked parallel with 3000watts Inverter (load)

Panels

Model NS-500S6-32
Maximum Power at STC(Pmax) 500W
Optimum Operating Voltage (Vmp) 48.63V
Optimum Operating Current (Imp) 10.29A
Open-Circuit Voltage (Voc) 59.0V
NSort-Circuit Current (Isc) 10.87A
Solar Cell Efficiency (%) 22.23
Solar Module Efficiency (%) 19.51
Operating Temperature -40to85℃
Maximum System Voltage DC1000
Maximum Series Fuse Rating 15A
Power Tolerance ±3% STC:Irradiance 1000W/㎡,
Modules Temperature 25℃,AM=1.5
 

FilterGuy

What, me worry?
My Battery is LiFePO4 48V, 400Ah hooked parallel with 3000watts Inverter (load)

Panels

Model NS-500S6-32
Maximum Power at STC(Pmax) 500W
Optimum Operating Voltage (Vmp) 48.63V
Optimum Operating Current (Imp) 10.29A
Open-Circuit Voltage (Voc) 59.0V
NSort-Circuit Current (Isc) 10.87A
Solar Cell Efficiency (%) 22.23
Solar Module Efficiency (%) 19.51
Operating Temperature -40to85℃
Maximum System Voltage DC1000
Maximum Series Fuse Rating 15A
Power Tolerance ±3% STC:Irradiance 1000W/㎡,
Modules Temperature 25℃,AM=1.5
OK, the 100A controller will handle 48V*100A=4800W on a low battery and/or 57.6V x 100A = 5760W on a full battery.
So, the controller appears to be reasonably well matched to the Array size.
10pcs of 500W in 2S5P setup.
My 12AWG running cable is only 30m

Isc is 10.87A. With the 5 parallel strings configuration that is 5 x 10.87A=54.35A. The working current is 5 X Imp = 5 x 10.29A = 51.45A
A 12AWG wire is unsafe at that amperage at any length. Is it getting warm/hot?

The NEC requirement for wire sizing is 1.55 x max Isc to the wire needs to be sized for 1.55 x 54.35 = 84.24. That means a *minimum* wire size of 4AWG.

To calculate voltage drop I use the Vmp and Imp. For your configuration the Imp is 5 x 10.29A = 51.45A and the Vmp is 2 x 48.63V = 97.26V
This means a 4 AWG should be OK for a 30M run between the panels and controller.

The 12AWG wire is certainly contributing to the power drop. Change that out and let us know what happens.

Note: You may want to review this:
 

abdallah.91

New Member
If I follow everything, you are getting ~78.6% of the rated power of your panels. That is better but not quite as much as I would expect.

That is a total of 75 amps which is much higher than I expected. Do you kno

If I follow everything, you are getting ~78.6% of the rated power of your panels. That is better but not quite as much as I would expect.

That is a total of 75 amps which is much higher than I expected. Do you know what the voltage is at the combiner box? Also, What is the ambient temperature?
please note that my inverter (Must PH18-5048 Plus) is 4000w maximum PV input power, and 5000w output power is 78.6% from 5000 or 4000w?
 

abdallah.91

New Member
Looks to me like you may be getting voltage drop on your wiring. Is it just me, or do the smaller gauge wires in your combiner box look discolored from heat?
Try using a busbar instead, and see what happens.
the difference in voltage between the combiner bow output and after the one thick cable was around 7 or 8 volts, but after I doubled the cable the difference reduced to 3V.
this was my combiner box when they were 3s4p. it is still the same box but now 2s6p.is there any problem in using like that modest box?
 

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FilterGuy

What, me worry?
please note that my inverter (Must PH18-5048 Plus) is 4000w maximum PV input power, and 5000w output power is 78.6% from 5000 or 4000w?
In the first post it was stated the panels are 4860W

The screenshot indicated the charger is putting out 3818W
1632693401035.png


3818/4860w=.786 = 78.6%
 

abdallah.91

New Member
If I follow everything, you are getting ~78.6% of the rated power of your panels. That is better but not quite as much as I would expect.

That is a total of 75 amps which is much higher than I expected. Do you know what the voltage is at the combiner box? Also, What is the ambient temperature?
today it was around 28 degrees celius. is it realistic that panels give just 0.4A in short circuit where the sun light hits them from that angle ( around an hour before sunset)??
 

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abdallah.91

New Member
In the first post it was stated the panels are 4860W

The screenshot indicated the charger is putting out 3818W
View attachment 66453


3818/4860w=.786 = 78.6%
ok but could the inverter take from these 4860w more than 4000w?
in reality I am not feeling comfortable with this inverter because that I ordered a Felicity IVEM5048 hybrid inverter with the Felicity Lifepo4 48200 battery. this inverter is compatible with their battery plus it can take 6000w pv panels power.
 
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