SRNE AIO - Winter production and MPPT behavior at low light

[Sleeper85]

Hello,

I have already posted about the behavior of my MPPT controller but a member thinks that my production is abnormal and suggested that I create a new topic.

My panels are oriented to the east on a roof with a slight slope of 15°, therefore on the blue line of the diagram below.



To the east is a hill and in winter the sun is visible only from 1 p.m. to 3 p.m. and at that time it is already low. (in the morning -10°C currently)

------------- 12h17 ------------------------ 14h40 ------------


Here is the ideal inclination for my city. (the worst exposure for a month of December)



I have an EAsun SMX II 5.6kW AIO ( SRNE HF4850S80-H rebranded ) connected to Solar Assistant (more info in my signature).

String of 8 Jinko 415WC panels (STC values) :

• WC = 8 x 415 = 3320WC
• Voc = 8 x 37.92 = 303.36V
• Vmp = 8 x 31,32 = 250,48V
• Imp = 13.25A

MPPT input voltage range 120~450 VDC.


So now I have two questions:

1. Is having a production peak at 300W (10% before 12h without sun) abnormal given the very poor exposure of my panels in winter? (after 1 p.m. when it was sunny I peaked at 600W)
2. My MPPT controller does not stabilize until I have at least 0.9A from PV, what do you think ? ( in low light the MPPT scans the voltage from high to low (90V) continuously)

Production of the day



MPPT behavior at low light







Thanks for your feedback

 

[Casteil]

So now I have two questions:

1. Is having a production peak at 300W (10% before 12h without sun) abnormal given the very poor exposure of my panels in winter? (after 1 p.m. when it was sunny I peaked at 600W)
2. My MPPT controller does not stabilize until I have at least 0.9A from PV, what do you think ? ( in low light the MPPT scans the voltage from high to low (90V) continuously)

I'm not sure I can address everything here, but given the following factors, I'm not surprised in the slightest that your production is low, nor by the fact that your system's only outputting ~10%

1. Your latitude (50 degrees - even worse winter sun hours than where I'm at @ ~43 degrees)
2. 15 degree panel angle (far from optimal for a low winter sun at high latitude - sunlight is hitting them at a very oblique angle so you're losing a lot of collection potential there)
3. Big hill to the east blocking virtually all morning sun

I think to get any reasonable collection in the middle of winter as we are now, you'd have to have your panels south-facing and at a fairly steep angle (i.e. ~70 degrees vs the ~15 degrees they're at now)

FYI: In your "Solar Angle Calculator" image, the angles shown there are measured off the vertical, not the horizontal as most people are referring to when talking about panel angle. So when they're indicating you should have a 15 degree angle for winter, what they mean is 90-15 or 75 degrees.

 

[400bird]

Ouch, your location is really hurting when combined with the shallow panel angle.

The hill definitely isn't helping, but wow. You are far north and your panels are very shallow.

PVWatts

Estimates the energy production and cost of energy of grid-connected photovoltaic (PV) energy systems throughout the world. It allows homeowners, small building owners, installers and manufacturers to easily develop estimates of the performance of potential PV installations

pvwatts.nrel.gov

Shows a peak of 300 watts for January 1st.
Pretty close to what you're seeing.

Is there any chance to reposition those panels? They'd to you much better mounted to a wall than a roof. But even then the hill and trees are going to block some production.

 

[Sleeper85]

Thank you for your answer, you reassure me.
Indeed when I spoke of 15° on another post, it was good in relation to the horizontal and I may not have been understood.

 

[Sleeper85]

From March April the sun will be there from daybreak. In winter it's very sad here, we even think about moving.

Any comment regarding question 2 and the behavior of the MPPT controller?

 

[HighDesertOffgrid]

From the photo, it looks like your panels are on the wrong side of the ridge line. Are they actually at 105 degrees?

 

[Sleeper85]

From the photo, it looks like your panels are on the wrong side of the ridge line. Are they actually at 105 degrees?

No +/- 75°

 

[400bird]

There a minimum for what the MPPT was programmed to search for.

I have no experience with Easun and haven't heard much about them.
But, you're producing something like 5% of it's rated output. That might be an edge case they didn't program for.

My Mindnite MPPT is currently receiving 0.4 PV amps and not doing what you're seeing.
The Solar Edge array (8kw) is making 198 watts and not doing what you're seeing.
So, I'd say the MPPT could be improved. But, I think you would get substantially more improvement from changing the panel angle.

 

[HighDesertOffgrid]

My panels are oriented to the east on a roof with a slight slope of 15°, therefore on the blue line of the diagram below.

No +/- 75°

I see. You are @ 75 degrees East but 90 degrees South. Southerly tilt would help immensely.

 

[Sleeper85]

Ok thanks for your comments. You confirm that my orientation is bad for winter and I understand that my MPPT controller is certainly not the best.

 

[Mattb4]

Hard to find fault with your charge controller when your panel location and access to direct sun is poor. The PV power graph you show indicates this as the unit keeps trying to create production and failing until near midday. If at all possible you should try to angle those panels to face the sun better.

 

[Quattrohead]

My Solark does exactly the same thing on both of my strings of panels, the voltage collapses when the MPPT tries to pull a load, rinse and repeat until there is enough sun on the string for it to hold up.
I could pull a set of charts from HA later on when I am on a real computer.
Even Florida is not as sunny some days as you would think.

 

[saen]

My MPPT start to work at 150V and turn of below 120V

and to be more real situation


It's very good to have weather station with show W/m² radiation

 

[Brightside]

I have this issue in low light as well. I can see it easily, because I have 4 identical strings and 2 other strings with 1 extra panel. All being exposed to the same filtered light on a cloudy day. I can see differences of a 100W or more between strings. where one is 50W and and the other 180W. Many times the lower power strings will have more than my higher power strings. It's frustrating, as I could be generating enough power for my loads and some battery charging, if the strings would lock in on a good power point.

Manufactures need a "Low Light" MPPT tracking algo. That you could manually set or even better would be to integrate an external solar sensor that would feedback to the MPPT the actual light conditions and than track accordingly. That would be ideal for winter solar production and essential for off-grid applications.

 

[Sleeper85]

My Solark does exactly the same thing on both of my strings of panels, the voltage collapses when the MPPT tries to pull a load, rinse and repeat until there is enough sun on the string for it to hold up.
I could pull a set of charts from HA later on when I am on a real computer.
Even Florida is not as sunny some days as you would think.

The voltage sawtooth, it looks very similar to my graphs.

 

[Sleeper85]

@RCinFLA left an interesting comment on this topic.

Is this normal or anything to worry about?

I'm new to solar and just recently purchased a Zendure Superbase 1500. I also bought two 12V 180W BougeRV panels. They have a VOC of 21V, I connected them in series and then connected to the Zendure via XT60 connector(which accepts 12-60V VOC). They are constantly going up to about 180W then...

diysolarforum.com

 

[RCinFLA]

The startup chopping power is in the same ballpark as total inverter overhead idle power. It may figure it is losing ground at that PV illumination power level so shut down and wait for illumination power level to improve.

It you are running inverter in standby mode where it can sleep the battery to HV DC converter when grid is available this makes sense. If you are continuously running inverter for immediate pickup load UPS mode operation it may keep the SCC active even though there is a net loss of power to battery since UPS mode has to spend the inverter idle power regardless of PV power being available or not.

The key is it needs to run the battery to HV DC converter to take the SCC HV DC output and convert it down to battery charging. Actual SCC board only takes 5-10 watts of overhead power, but battery to HV DC converter needed to charge battery, takes a lot more overhead power.

Another thing you might try is just adding a little AC load and see if it keeps SCC running. It takes less overhead power to go from PV to AC output supplementing than PV to battery charging, because it does not need to run the battery to HV DC converter.

 

[Sleeper85]

Very interesting, for the moment my AIO is in UTI mode (bypass) with battery charge in OSO mode (Solar only). I will try to do a test to highlight what you say.

 

[Sleeper85]

@RCinFLA what you said is absolutely true, it is indeed the "HV DC to Buck Battery Charger" component that needed more power to initiate a charge with a lot of amps (when there is a big difference between "charge voltage" and "battery voltage").

With my AIO I don't have an option to disable battery charging from solar (no "utility only" option). Tip: to disable battery charging, I set the "charge voltage" a bit lower than "battery voltage".

With this configuration and a small AC load the SCC MPPT stabilizes directly with less than 0.1A because it does not need much power to start charging the battery.

A, B, C, E : SCC MPPT follows load demand
D : the load demand is a little too large, the SCC MPPT stalls several times, the battery gives the power difference.



For the screenshot below, it will be better when the BMS is connected to Solar Assistant

 

[Adrian R]

My EASUN SMG 2 5,6KP on a string of 10 panels about 2300 wp and 322 Voc on a cloudy day has a peak of maybe 100 watts and below 35-40 watt doesn't even start or already stops production around 3 pm

Is this a normal behavior for an AIO?

Do you experience a similar situation?

Thank you