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94watts More than PV Panel Rating?
#1
Hello from USA! I just purchased an inexpensive 20A MPPT controller from Rich Solar. Specs indicate max pv input is 250w and 100v for 12v system (Flooded), so I connected 2x100watt panels in series. The app has recorded 294watts max today and frequently indicating well over 200w. I'm confused...? maybe faulty sensor in Controller?

My 40amp Renogy MPPT Rover rarely achieves 50% of the panel ratings. On this controller I have 4x100watt panels in series and lucky to get 240watts on a perfectly clear day. My Renogy junk?

Thanks for any help understanding this.
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#2
(09-27-2020, 07:54 PM)1xAA Wrote: Hello from USA! I just purchased an inexpensive 20A MPPT controller from Rich Solar. Specs indicate max pv input is 250w and 100v for 12v system (Flooded), so I connected 2x100watt panels in series. The app has recorded 294watts max today and frequently indicating well over 200w. I'm confused...? maybe faulty sensor in Controller?

My 40amp Renogy MPPT Rover rarely achieves 50% of the panel ratings. On this controller I have 4x100watt panels in series and lucky to get 240watts on a perfectly clear day. My Renogy junk?

Thanks for any help understanding this.
I've seen momentary bursts a little over max on certain conditions - like cool days when the sun is coming in/out of clouds and the controller will show short bursts as it finds MPPT..   if you getting this sustained...  then I would suspect the controller is off a bit Smile

One way to research this is to do an independent measurement - e.g. maybe install cheap ($17) shunt w/meter to give an independent reading such as this https://www.amazon.com/Digital-Multimete...Y2s9dHJ1ZQ==.
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#3
(09-27-2020, 08:27 PM)OffGridInTheCity Wrote: I've seen momentary bursts a little over max on certain conditions - like cool days when the sun is coming in/out of clouds and the controller will show short bursts as it finds MPPT..

I've observed those situations, too. I believe it's due to the panels receiving 100% direct sunshine from the sun, as well as additional diffused light from the clouds.  So in sum it's receiving more light than under laboratory test conditions.

A cool panel can also output more power, about 0.5% more for every degree cooler than test condition (25C?).  Look for "Temp coefficient" in the spec sheet.

Also, reputable manufacturers will generally understate the power output by at least a few Watts.

But 294W/200W does sound very optimistic.  You could use a clamp meter (make sure it's for DC) to measure current and multimeter to measure voltage. Both are very useful tools.
Modular PowerShelf using 3D printed packs.  60kWh and growing.
https://secondlifestorage.com/showthread.php?tid=6458
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#4
When you say "the app has recorded 294 watts max today" this is over a period of time not instant power.
eg, if the panels were producing 90W now & they did this for 4 hours, you'd see the app say approx 360WHrs power collected and that would be 100% normal.

Re the panels instantaneous output, like others have posted, it's mainly about panel temperature & possibly diffused light, also it's new.
If the panel is colder than the test temperature (25degC for STC or 44degC for NOCT) eg on cold day or the sun just popped out from behind clouds you'll get more W.
If the conditions are lightly hazy but bright, you can get more W.
When panels are new you can get a few % (eg 3-5%) more W. As it ages, this will gradually drop over a few years.
Running off solar, DIY & electronics fan :-)
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#5
Thanks for the replies. I have a  meter here I will wire in. Been wanting a clamp meter for a while now, perfect excuse! Smile

No mate (redpacket), "Max Char Power" was "294W".  Total generated today was 1504 kWh. These mono panels are 2 years old now.

This Rich Solar is WAY high and the Renogy is too low. These controllers seem to be the same just rebranded.

Side note: Purchased a "20W" panel for 12v batteries to keep my lawn mower battery topped off, It is "20W" IF 3.504W is 20watts. Gotta love the marketing! Smile
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#6
(09-27-2020, 11:42 PM)1xAA Wrote: Thanks for the replies. I have a  meter here I will wire in. Been wanting a clamp meter for a while now, perfect excuse! Smile

No mate (redpacket), "Max Char Power" was "294W".  Total generated today was 1504 kWh. These mono panels are 2 years old now.

This Rich Solar is WAY high and the Renogy is too low. These controllers seem to be the same just rebranded.

Side note: Purchased a "20W" panel for 12v batteries to keep my lawn mower battery topped off, It is "20W" IF 3.504W is 20watts. Gotta love the marketing! Smile

OK, must be a good size metering error in the Rich unit then I guess!
Does the unit give you current & voltage readings?
You might be able to put a 10A multimeter in series to get the current & another meter to measure the volts.

re the low Renogy readings, what angle to the sun are the panels at mid day?
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Running off solar, DIY & electronics fan :-)
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#7
Figged out... voltage sense is correct on the charge controller, BUT the current sense is WAY-WAY-WAY off! Like 10x in one instance, i.e. ".10" amp (very cloudy) on the meter connected to PV lines and the charge controller is sensing "1" amp-Yes 1amp. Sending Rich Solar a nice message. Will update with their response.

Interesting, now I need to check that Renogy as well.

As far as the angle, I change them every season based on 37th parallel north-can't remember what the angles were, but I just adjusted the angle for Fall season.
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#8
Could it possibly be that you have the opposite set of panels wired to the charge controller that you think they are wired to. I’m saying could you have mistakenly wired the wrong array to the wrong controller? Then the watts you are seeing from each controller would make sense.
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#9
To clarify, is it possible the Renogy is using the two 100w panels and the Rich solar is using the four 100w panels
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#10
Did some more monitoring today with the meter on the PV lines and compared it to what the controller information is reporting. It appears the app is multiplying the wattage from the PV panels by the current going into the batteries NOT the current from the PV panels. The current from the controller to the batteries is at a significantly lower voltage much closer to 14v rather than the 30V+ coming from the panels. uhm...is this how we calculate watts from panels? If so, I have been doing it wrong for two years now and everything else no longer makes sense. Maybe-really reaching here-the app is miscommunicating with the BT app on my phone and providing the wrong current reading-kinda like a software error? Rich Solar doesn't even provide an app, they tell their customers to use Renogy or SRNE. The only thing I see from their website is an RS232-USB interface. ugh, maybe Rich Solar is a little bit TOO inexpensive?

Cheap4 life, I thought the exact same thing so I double-checked to make sure I had exactly two panels in series and I had them correct; I had exactly two panels in series.
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