How much solar power should I expect from 500W panels

Usangira

New Member
Hi
For almost six months now I have 10 panels of 500W with below specifications

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

Recently I had interest to check how much are the 10panels producing per hour/day

Surprisingly, through my SCC I can only see 2200w during peak hours (around mid day) while I expected it to be close to 4000w

Can somebody guide me here. I am in Dar es Salaam with almost 10hrs of sunlight per day through out the year

Thanks, Innocent
 

Frick

Solar Enthusiast
Hi,
there are many variables that will change the output. total load on the panels, temp, wiring configuration, type of hardware a d batteries, etc.. could you post some pics, list of equipment, and a drawing showing how it’s all connected? That would help a lot into diagnosing your situation.
 

stienman

Solar Addict
Frick is right, we can't begin to help until we know how the entire system is set up. For instance, I'm using an off-grid inverter. Once the batteries are full, it will only use as much solar as I'm consuming. So while I have a 7kw array, I might only be getting 2kw during the peak of a sunny day because that's all I'm using out of the inverter.
 

gfmucci

New Member
About 75% of their rated value. ~4000 watts. Sort of like the quest for perfection: Most of us hope to approach it knowing the impossibility of achieving it.
 

OffGridInTheCity

Solar Addict
New panels. After 3 years of operation I observe....
On clear'ish hot summer days... I get at least 80% of the rated PV on typical summer days. I attribute 5%'ish of that 'loss' to sub-optimal angle + dust on them. 10% of that is likely HEAT 90-100F/32-38C - this is a noticeable factor day to day. Another 5% - maybe smoke/cloud/general haze even on clear days Or maybe inaccurate charge controller reporting OR who knows exactly. Weather is much more variable than I would ever have imagined before doing this solar system and affects power hour to hour.

I have gotten 100% of rated power in spring / cool days here and there for a couple of hours :)
 

Usangira

New Member
Frick is right, we can't begin to help until we know how the entire system is set up. For instance, I'm using an off-grid inverter. Once the batteries are full, it will only use as much solar as I'm consuming. So while I have a 7kw array, I might only be getting 2kw during the peak of a sunny day because that's all I'm using out of the inverter.
Thank your all

Attached is my drawing with the specifications I have. Hopefully it is informative enough

Thanks
 

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OffGridInTheCity

Solar Addict
Can you share details on your Charge Controller / Battery-bank / setup. Looks like you're showing an off-grid setup? Is your battery full? (what's the voltage range you're using).

As mentioned above, the Charge Controller will throttle input if you're not using PV and your battery is full.
 

Usangira

New Member
Can you share details on your Charge Controller / Battery-bank / setup. Looks like you're showing an off-grid setup? Is your battery full? (what's the voltage range you're using).

As mentioned above, the Charge Controller will throttle input if you're not using PV and your battery is full.
Hi
Yes, it is off-grid setup

My batteries never get full before 1500hrs.

SCC operate stops BULK charging at 55.2V, It shuts off automatically is voltage goes below 42V while the inverter shuts down at 40V
My LiFeO4 bank is 48V, 200AH

Thanks
Innocent
 

OffGridInTheCity

Solar Addict
Hi
Yes, it is off-grid setup

My batteries never get full before 1500hrs.

SCC operate stops BULK charging at 55.2V, It shuts off automatically is voltage goes below 42V while the inverter shuts down at 40V
My LiFeO4 bank is 48V, 200AH

Thanks
Innocent
Can you share details (model and specs) on your SCC? Maybe the 2s voltage range or overall wattage coming in does not match very well.
 

Usangira

New Member
My SCC operates to the maximum of PV 5000W, 150V.
My panels each has 59V (open circuit) and I get around 101V during peak (as it is 2S)
 

OffGridInTheCity

Solar Addict
My SCC operates to the maximum of PV 5000W, 150V.
My panels each has 59V (open circuit) and I get around 101V during peak (as it is 2S)
OK so we have PV input voltage and total watts consistent with what the SCC can accept and Voc is 101v'ish is comfortably higher than the max battery voltage. *FYI - can you share the model of SCC?, maybe someone will be familiar with settings to check.

Some possible issues that come to my mind to check off:
The PV array....
- Is there shading of any kind - is the angle at least 20deg - are they panels damaged - is the wiring not as assumed/bad-connections - are they dirty or do you get consistent clouds.... - e.g. is anything in the way of normal panel power production.
- If above OK, then suggest you test each string in isolation. A single string 2s1p (1000w) should at least get 800w'ish actual. If each string is only 400w and this is consistent then its less likely to be a single string (or 2) pulling things down. If you have a combiner box - it may be as simple as disconnecting the combined strings and then re-connecting each one in isolation...

The Load/Battery....
You've indicated there is load / battery is not fully charged. Maybe the battery is 'nearly' charged? and so even if its not fully charged you're in CV mode and full power is not flowing to the batter/load.

The Charge Controller...
- Settings? My charge controllers (Midnite Classic) have settings to let me throttle PV input and output - so it would only do a % of available PV solar. Maybe you have settings like this?
- IF all the above - maybe the SCC is broken? cah you try a different charge controller - maybe in conjunction with 2s1p single string test) above.

I do believe that something is amiss - just hard to tell exactly what so far.
 
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Usangira

New Member
I am kinda confused.....

I am using a Chinese SCC from SMK Solar (Its picture and specs attached)

I never get shaded. My solar panels work as car park shade.

This morning my battery was 68% full and I was running a lot of around 2000W from an inverter. Yet the SCC was producing only 850W. At this stage I expected the scc to be at its maximum capacity as the sky was completely "clear" blue

I live in Dar es Salaam a region where is has got plenty of solar hours ( around 4KWh per a square meter per day while my panels have covered 22 square meters of area)

And may be somebody should help me to understand the I/V curves attached. If my operating voltage is 101V for 2S which means is around 50V per what does it mean in output on the left of the graphs?

Thanks

Innocent



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1627371569553.png
 

stienman

Solar Addict
So here are some thoughts that might lead to resolution, though I know you've already gone through some of these steps:

500W panels are HUGE and new to the market. I'd test each panel individually to make certain they meet their spec. Are they really 1.9m x 1.3m?

You're running 5 parallel series pairs of panels, so you should see 120V open circuit voltage and 50A short circuit current at the charge controller. Confirm that this is the case. Make sure the cables carrying that 50A current have the capacity to do so without a significant voltage drop. 6awg solid copper is the smallest wire for that job, but if the cable run is over 25 feet you should be using larger conductors (4awg or 2awg) to avoid power loss in the cables. 5kw to 850w is exceptional, so that can't be the whole story.

I expect you're using a combiner box to connect all these pairs together. If you're using MC3 combiners be aware they are not rated for this current. Each pair should be fused, so double check that all the fuses are in good condition. Again, you should see 50A short circuit current at the charge controller - measure it carefully (you WILL draw a large DC arc if you use test leads) - but do measure it. I recommend turning the breaker off, shorting it after the breaker, putting a DC current clamp meter around the shorted wire, then flipping the breaker on for a few seconds to confirm the current. This will contain the arc inside the breaker, which should be rated for the DC current and voltage you're protecting with it. The shorting wire will need to be 6awg or 4awg, just like the rest of the wire between the panels and the charge controller.

Once you've confirmed that you're getting the rated voltage and current at the charge controller, then measure the charge controller's output current and voltage. You can't always depend on what the charge controller is saying - measure everything with a trusted meter and confirm what the system is telling you.

The current could be as high as 100A. This means the wiring between the controller and the battery has to be 4awg copper if the run is short. If long, use 2awg. Don't short the output of the charge controller - just measure it while its charging the batteries.

Hopefully you're using solid copper wire and not aluminum or "copper clad aluminum" (CCA) which is just aluminum that has fewer problems with mixed metal connections, but not as good at carrying current.

If the input to the charge controller looks ok, and output does not, then there's most likely a problem with the charge controller, either within its settings, or it is somehow damaged.

There is one other possibility. If the resistance between the charge controller and the battery is high, for instance through a thin and/or long cable, high resistance fuses/switches/etc, or the battery has high internal resistance, then the charge controller may think the battery's voltage is high enough to charge at a slower rate. Check the voltage along the positive wire from the charge controller to the battery and make sure you don't see more than a few mV drop through all the wiring and components. Also check the internal resistance of the battery.

What are you using to determine the state of charge of your battery? You can't rely on voltage alone, but need a shunt or current sensing based coulomb counter.

Hopefully this helps.
 
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