Does this seem like low production for panels on my 5th wheel?

[BretS]

Pulled my 5th wheel out into full sunlight at solar noon to test my solar production. I have 2 arrays, each has 3 350W Hanwha Q panels in series going to a Victron 150/70 Smartsolar MPPT controller. The wiring from the panels to the breakers is 8 AWG that I bought from Windy Nation with MC-4 connectors already installed. From the breakers to the controllers, and controllers to the Lynx, I used 4 AWG wire because I had it on hand. All wires to the breakers and controllers have crimped ferules on them.

I saw around 1400W for both arrays, give or take a little, for the hour I had it in the sun. The forward and aft arrays both performed pretty evenly, with the forward being maybe 15-20W higher most of the time. There was no shadowing on any of the panels the whole time. The panels were clean and there wasn't a cloud in the sky. My battery bank (850Ah LiFePO4 at 12V) was at 25%, so the chargers were in bulk. I have had a couple of people familiar with these panels, and my layout, tell me that I am getting a low production, and they would expect it to be around 1800W.

Does this actually seem low? If so, any ideas on what could be causing this? Pics below (pics not taken while it was in the sun) and panel data sheet attached. TIA!

 

[jwelter99]

What is open circuit voltage on both strings? Should be 121V in reasonable sun.

 

[Lt.Dan]

With us getting out of the summer months I have noticed a 20-30% drop in PV production on my roof mounted panels, whereas my ground mount (tilted at 35*) is only down ~10%.

 

[BretS]

What is open circuit voltage on both strings? Should be 121V in reasonable sun.

I didn't pull the breaker box cover back off to check it at the top side in full sun with the breaker open. But the panels are in the mid 30's when I checked them unplugged. So, about 5V under Voc. Is that an indication of subpar panels if the reading is lower than the spec Voc? How much does temperature effect that?

 

[BretS]

With us getting out of the summer months I have noticed a 20-30% drop in PV production on my roof mounted panels, whereas my ground mount (tilted at 35*) is only down ~10%.

Thank you, that is good info! From what they tell me I should be, if I am down 20% now, that would put me about right in the summer.

 

[RV10flyer]

I’m at 38 deg. That’s normal depending on your latitude, elevation, humidity, temperature. A lot of variables.

 

[jwelter99]

I didn't pull the breaker box cover back off to check it at the top side in full sun with the breaker open. But the panels are in the mid 30's when I checked them unplugged. So, about 5V under Voc. Is that an indication of subpar panels if the reading is lower than the spec Voc? How much does temperature effect that?

My experience is for panels in any sort of decent sun you should be close to the open circuit voltage if nothing connected. It is when loaded that the voltage will fall based on solar conditions.

If you are not getting close to Voc with no load you might have a wiring or panel issue.

 

[BretS]

My experience is for panels in any sort of decent sun you should be close to the open circuit voltage if nothing connected. It is when loaded that the voltage will fall based on solar conditions.

If you are not getting close to Voc with no load you might have a wiring or panel issue.

Looking at the chart, I am within 2-3V of Voc for normal operating conditions and within 4-5V of Voc for standard test conditions. My temperature was definitely closer to their normal condition than their standard conditions. Would you call that close enough to rule out panel or wiring issues?

 

[eXodus]

Pulled my 5th wheel out into full sunlight at solar noon to test my solar production. I have 2 arrays, each has 3 350W Hanwha Q panels in series going to a Victron 150/70 Smartsolar MPPT controller. The wiring from the panels to the breakers is 8 AWG that I bought from Windy Nation with MC-4 connectors already installed. From the breakers to the controllers, and controllers to the Lynx, I used 4 AWG wire because I had it on hand. All wires to the breakers and controllers have crimped ferules on them.

I saw around 1400W for both arrays, give or take a little, for the hour I had it in the sun. The forward and aft arrays both performed pretty evenly, with the forward being maybe 15-20W higher most of the time. There was no shadowing on any of the panels the whole time. The panels were clean and there wasn't a cloud in the sky. My battery bank (850Ah LiFePO4 at 12V) was at 25%, so the chargers were in bulk. I have had a couple of people familiar with these panels, and my layout, tell me that I am getting a low production, and they would expect it to be around 1800W.

6x 350 = 2100W
Yours are flat - so you never get full output when you are not close to equator.
What do you mean 2 arrays? Do you mean strings? Do you got two victron MPPT?

With those large panels I started getting multiple smaller MPPTs instead of one large one. In non mobile application it's already common to have one MPPT per panel. (Enphase IQ Series)

The more panels you got per MPPT - the worse your output is getting when you got a little shade and you got a ton of objects on the roof which is producing shade. (two A/Cs and fan covers)

I would split up your panels - in at least 2 better 3 MPPTs then you should get more production out of them.

 

[BretS]

6x 350 = 2100W
Yours are flat - so you never get full output when you are not close to equator.
What do you mean 2 arrays? Do you mean strings? Do you got two victron MPPT?

With those large panels I started getting multiple smaller MPPTs instead of one large one. In non mobile application it's already common to have one MPPT per panel. (Enphase IQ Series)

The more panels you got per MPPT - the worse your output is getting when you got a little shade and you got a ton of objects on the roof which is producing shade. (two A/Cs and fan covers)

I would split up your panels - in at least 2 better 3 MPPTs then you should get more production out of them.

I have 2 MPPTs with 3 panels on each.

 

[jwelter99]

Looking at the chart, I am within 2-3V of Voc for normal operating conditions and within 4-5V of Voc for standard test conditions. My temperature was definitely closer to their normal condition than their standard conditions. Would you call that close enough to rule out panel or wiring issues?

Yes most likely. The other quick test is a blanket or towel and put it over one panel at a time during your solar hours and see if each time the output goes down by about 1/3rd of the string total without any covering. You are looking for any single panel that contributes more or less then the others.

 

[cinergi]

I'm peaking at 2300 watts for my 3350 watt array up here near Yellowstone right now. 69% of rated. You're getting about 67%. Depending on your location, that seems normal for ~12:00-1:00pm.

 

[BretS]

I'm peaking at 2300 watts for my 3350 watt array up here near Yellowstone right now. 69% of rated. You're getting about 67%. Depending on your location, that seems normal for ~12:00-1:00pm.

I'm in MD, near Washington DC... probably a lot of BS in the air blocking my production 🤣

 

[jwelter99]

I'm in MD, near Washington DC... probably a lot of BS in the air blocking my production 🤣

I'm in Annapolis and just did a test. I have 1800W of solar panels (4 of the 450W Rec Alpha 72 panels). They are setup with 2 strings of 2 in series each off a MPTT - so 900W per MPTT. Each MPTT is a Victron 150/100v2 on latest firmware.

Voc is 53.1V per panel from the specs (106.2V for 2s). Just measuring at the PV disconnect input with the breaker turned off I get 106.6V and 106.3V on the two strings. So right at the specified.

With the PV re-connected Vmpp is at 88.6V for the string with 91.2V being the rated from specs.

Power output is 844W on one string, and 837W on the other string - about 93% of rated output.

All wiring is 8AWG with self-crimped connectors.

 

[BretS]

I'm in Annapolis and just did a test. I have 1800W of solar panels (4 of the 450W Rec Alpha 72 panels). They are setup with 2 strings of 2 in series each off a MPTT - so 900W per MPTT. Each MPTT is a Victron 150/100v2 on latest firmware.

Voc is 53.1V per panel from the specs (106.2V for 2s). Just measuring at the PV disconnect input with the breaker turned off I get 106.6V and 106.3V on the two strings. So right at the specified.

With the PV re-connected Vmpp is at 88.6V for the string with 91.2V being the rated from specs.

Power output is 844W on one string, and 837W on the other string - about 93% of rated output.

All wiring is 8AWG with self-crimped connectors.

Are yours flat on an RV roof?

 

[jwelter99]

Are yours flat on an RV roof?

They are mounted straight up with a 2.5 inch gap between panels and roof.

 

[BretS]

They are mounted straight up with a 2.5 inch gap between panels and roof.

93% is awesome! Wish I was seeing numbers like that!

 

[Sojourner1]

Do you really need to see #s like that? Running in a psoc isn't going to hurt the lfp's.

My 2s4p 1,280w (160w panels) in sunny conditions produce 900-1,150w max during most of summer and shoulder seasons, during winter 700-1,000w but have to pay attention to the direction the 5th wheel is pointed for the sunrise to get the most out of production with the shorter daylight hours. Shoulder seasons/ summer it doesn't really matter too much but try to have the door side of trailer facing east but don't go out of my way for the max production.
Here is an example for this month in SD fulltime boondocking.

 

[cinergi]

I'm in Annapolis and just did a test. I have 1800W of solar panels (4 of the 450W Rec Alpha 72 panels). They are setup with 2 strings of 2 in series each off a MPTT - so 900W per MPTT. Each MPTT is a Victron 150/100v2 on latest firmware.

Voc is 53.1V per panel from the specs (106.2V for 2s). Just measuring at the PV disconnect input with the breaker turned off I get 106.6V and 106.3V on the two strings. So right at the specified.

With the PV re-connected Vmpp is at 88.6V for the string with 91.2V being the rated from specs.

Power output is 844W on one string, and 837W on the other string - about 93% of rated output.

All wiring is 8AWG with self-crimped connectors.

wow that's crazy high. What was the temperature? Do you know what you were seeing mid-June?

 

[jwelter99]

93% is awesome! Wish I was seeing numbers like that!

Today is really overcast but still pretty bright out.

I did the voltage measurements again 105.1V and 105.7V for Voc with open load. So still pretty close to theoretical even in "poor" sun. Temp is 22C which is below my test yesterday, which was around 27C.

Solar production is at 331W on one string, and 338W on the other string. Still enough to top batteries back up , and the excess to keep the hot water tank hot.

Also not sure that 93% is that great, as this system in strong sun earlier this summer was routinely putting out above 1800W during peak hours.

I talked to REC about this as well as a couple others and they said this is pretty normal to get over rated when new for two main reasons:

1) To ensure the panels meet their performance warranty over their lifetime - they understate their output to get some headroom.

2) As the production processes mature and stabilize the panels get better, and we see new power ratings released. These Alpha 72's started at 425W and then they have stepped up all the way to 450W which I am using. I am told they will be releasing to 480W shortly, and the 430 to 445 discontinued. Basically the range they offer covers the worse to the best output yields.