Is my solar production throttled?

[MooreN]

I have a recently installed system with two strings of 9 x 400w panels, controlled by a Schneider XW-Pro 6848 inverter, MPPT80 charge controller and a Fortress eVault 18.5 battery.
I monitor and can configure through InsightLocal v 1.16
I am set up to sell to grid with Grid Support enabled at 65v and SOC 85%, Peak Load Shave enabled at 0 amps.
I am learning about balancing SOC, battery charging, grid input and load.

But my question revolves around the power I am getting from my panels.
The 18 x 400w suggest a maximum of 7.2kWh and I assume the XW inverter will reduce that to a max of 6.8 kWh.
But I keep seeing a max around 4.8kWh - at 13:00hrs on a warm (90F) Texas day with clear skies.
Initially the installation was not configured to use the BMS or sell to grid. However Fortress talked me through that and on that day I briefly saw a production of 6.8 kWh. But since then it seems to be throttled at 4.8

Are there any settings that would affect this? I am a novice and would appreciate any guidance.

 

[BentleyJ]

It depends on total demand from the loads and battery charging combined. The charge controllers only produce what is being consumed at a given output voltage, they cannot force more current through the system than what is needed.

If the batteries are in the upper end of the charge range, current will begin to taper off.

Feel free to post more detailed information or post some screen shots of the set up menus and power flows. This help you get more specific feedback.

 

[seneysolar]

I have a recently installed system with two strings of 9 x 400w panels, controlled by a Schneider XW-Pro 6848 inverter, MPPT80 charge controller and a Fortress eVault 18.5 battery.
I monitor and can configure through InsightLocal v 1.16
I am set up to sell to grid with Grid Support enabled at 65v and SOC 85%, Peak Load Shave enabled at 0 amps.
I am learning about balancing SOC, battery charging, grid input and load.

But my question revolves around the power I am getting from my panels.
The 18 x 400w suggest a maximum of 7.2kWh and I assume the XW inverter will reduce that to a max of 6.8 kWh.
But I keep seeing a max around 4.8kWh - at 13:00hrs on a warm (90F) Texas day with clear skies.
Initially the installation was not configured to use the BMS or sell to grid. However Fortress talked me through that and on that day I briefly saw a production of 6.8 kWh. But since then it seems to be throttled at 4.8

Are there any settings that would affect this? I am a novice and would appreciate any guidance.

Surely you have more than 1 charge controller?

 

[chrisski]

Could be normal.

I am seeing something similar to that in Arizona with10 kw of panels just producing 6.2 kw.

Take a guess at your orientation of your panels and put them through a solar calculator like PV watts or the one in my signature block.

Also your inverter will only run max rating for so long and likely derates constant output to 80% and may derate further for hit temps.

 

[MooreN]

It depends on total demand from the loads and battery charging combined. The charge controllers only produce what is being consumed at a given output voltage, they cannot force more current through the system than what is needed.

If the batteries are in the upper end of the charge range, current will begin to taper off.

Feel free to post more detailed information or post some screen shots of the set up menus and power flows. This help you get more specific feedback.

Thanks.
Here are my power flow, current status and xw config.
I am getting 4.4 kW in bright Texas sunshine.

Any feedback welcome

 

[MooreN]

Surely you have more than 1 charge controller?

I assumed the MPPT80 is designed for this load?

 

[MooreN]

Could be normal.

I am seeing something similar to that in Arizona with10 kw of panels just producing 6.2 kw.

Take a guess at your orientation of your panels and put them through a solar calculator like PV watts or the one in my signature block.

Also your inverter will only run max rating for so long and likely derates constant output to 80% and may derate further for hit temps.

I am trying to figure out what normal is!
You are getting ~60%, which is similar to my numbers.
Is there a setting which controls the derate you refer to?

 

[BentleyJ]

There are several detailed posts on the forum regarding Enhanced Grid Support not working properly with regard to discharging the battery when that shouldn't happen. Although based on the Power Flow screen shot your battery SoC is 86% which is still above the 85% Grid Support Setting. The concern comes in when the battery keeps discharging even after the SoC falls below the set point. Does battery discharge stop if you raise the set point to 90% SoC?
Would recommend doing a couple of forum searches and read what others have found as far as problems and solutions.

The house load is only 2.2kW and solar is producing 4.4kW so excess solar will go out to the grid. Battery discharge is not necessary.

Sell Amps is set to 27A so this is not limiting export. It seems like with a 7.2kW system there should be more solar but as chrisski said there are many factors. Its hot in Texas today, PV output goes down as temp goes up.

 

[MooreN]

There are several detailed posts on the forum regarding Enhanced Grid Support not working properly with regard to discharging the battery when that shouldn't happen. Although based on the Power Flow screen shot your battery SoC is 86% which is still above the 85% Grid Support Setting. The concern comes in when the battery keeps discharging even after the SoC falls below the set point. Does battery discharge stop if you raise the set point to 90% SoC?
Would recommend doing a couple of forum searches and read what others have found as far as problems and solutions.

The house load is only 2.2kW and solar is producing 4.4kW so excess solar will go out to the grid. Battery discharge is not necessary.

Sell Amps is set to 27A so this is not limiting export. It seems like with a 7.2kW system there should be more solar but as chrisski said there are many factors. Its hot in Texas today, PV output goes down as temp goes up.

Thanks, I will research the forum.
FYI, here are two screen shots (from 5/18 and 5/20) showing quite different SOC behavior although in both cases the SOC was set to 85%.
After the first, on 5/18, I changed the grid support from 52v to 65v and enabled peak load save with 0 amps between 01:00 and 07:00. I did not realize that SOC would be affected.

I am surprised that PV goes down as temp goes up, why is that?

 

[yodamota]

I assumed the MPPT80 is designed for this load?

your mppt80 is only designed to output 80amps. The charge controller is only able to output up to that amount. I would assume you are exporting exactly what your charge controller can contribute to keep the voltage above the export setpoint.

have you looked at the tech document on your charge controller?
the 600/80amp SE charge controller says max output is 4800w. Id be getting another charge controller if you would like to output more power

 

[MooreN]

your mppt80 is only designed to output 80amps. The charge controller is only able to output up to that amount. I would assume you are exporting exactly what your charge controller can contribute to keep the voltage above the export setpoint.

have you looked at the tech document on your charge controller?
the 600/80amp SE charge controller says max output is 4800w. Id be getting another charge controller if you would like to output more power

Bingo! That makes a lot of sense - and explains the apparent throttling at around 4.5/4.6 kW.
Thanks

 

[BentleyJ]

I am surprised that PV goes down as temp goes up, why is that?

Take a look at the Datasheet for the 400W PV panels you are using (or any others) In addition to the voltage and current specs there will be a value for Temperature Coefficient. Something like this -0.35% / deg C.

Note the Neg sign. means voltage goes down as module temp goes up. Has to do with internal resistance increasing with higher temps. Also, because the coeff is negative, low temp Voc (which is determined at 25C) has to be re-calculated for cold climates so the voltage doesn't climb and exceed the charge controller maximum input voltage.

 

[Bop]

Not a particularly well matched system...
The Fortress is a 48v nominal LFP battery, but its peak current is only 200A (max load limit of 9600W) while your XW Pro can pull peaks of 12kW for up to a minute (so peak loads will be over the Fortresses maximum peak, hopefully its BMS will shut down and protect it)

And as others have noted, your MPPT charge controller is seriously undersized for the solar array...
W=VxA, 48v nominal (charge voltage around 57.5v) x 80A = 4600w while your solar array is a nominal 18 x 400w =7200w

The charge controller rating is its OUTPUT, and so no matter how much you feed it, it will only ever put out about that 4600w- effectively in good weather, the rest of the panels are decorative...
(you will find them handy in poor weather conditions however ie overcast or raining- they will deliver more generated power in those conditions than a matched string)

Another thing is that the '400w' rating is only at STC or standard test conditions ie panel cell temp of 25C, solar illumination of 1000W/m^2 and an atmospheric mass of 1.5 (the thickness of the earths atmosphere vertically from sealevel to space is 1AM)- if ANY of these are different, then the actual power output is different...

As others have noted, the temp makes a major different (panels are around -0.4% per degree Celsius temperature rise) so effectively the hotter the panels get, the less power they make (my panels here in Australia have been measured in summer at over 80C, which at a -0.4% per degree C, means that they are under 200W instead of their STC rating of 250W!!!- 1/5 of their 'power' lost!!!)

If you live on top of a mountain range, your apparent power goes up, at sealevel it goes down, the hotter it is, the less power you make, the further north in the northern hemisphere, or south in the southern hemisphere, the less power you get (up to a certain point- once you get to cold areas where snow is present, your power starts to climb again even with the lower solar insolation, you get both reflected light and cooler panels offsetting the lower light levels...)