Low harvest problem

[benjieg]

Greetings. Hoping to find some help from the group.

My setup is:
450W x 10 panels in series (correction: 10 panels later confirmed to be connected in 5s2p configuration)
Voc = 49.6V, Vmp = 41.0V
Isc = 11.53A, Imp = 10.98A
MPP Solor 5KVA Inverter
Blue Carbon 48V 200AH batter

I'm getting fairly good sunlight with blue skies. On my Inverter screen, I'm seeing only around 170V and 2000W of peak power during noon time. I'm thinking this is somewhat on the low end. Do you think there's a problem and if so, where do I start looking?

 

[Bud Martin]

Greetings. Hoping to find some help from the group.

My setup is:
450W x 10 panels in series
Voc = 49.6V, Vmp = 41.0V
Isc = 11.53A, Imp = 10.98A
MPP Solor 5KVA Inverter
Blue Carbon 48V 200AH batter

I'm getting fairly good sunlight with blue skies. On my Inverter screen, I'm seeing only around 170V and 2000W of peak power during noon time. I'm thinking this is somewhat on the low end. Do you think there's a problem and if so, where do I start looking?

1) What is the max PV input spec of the SCC?
2) Make and model of the SCC?
3) You have 10 panels in series, and each panel has Voc of 49.6V, and Vmp of 41V so the Voltage should be higher than 400VDC but you only getting 170V. Are you sure that they are all connected in series or may be measurement error?
4) What is the battery charging current you are seeing during 2000W peak? Were the batteries are almost full? Do you see the Wattage go up if you run the heavy load?

 

[benjieg]

1) What is the max PV input spec of the SCC?
2) Make and model of the SCC?
3) You have 10 panels in series, and each panel has Voc of 49.6V, and Vmp of 41V so the Voltage should be higher than 400VDC but you only getting 170V. Are you sure that they are all connected in series or may be measurement error?
4) What is the battery charging current you are seeing during 2000W peak? Were the batteries are almost full? Do you see the Wattage go up if you run the heavy load?

Hi Bud, thank you for your response.

I have an MPP Solar 5048GK. Max Solar Voltage or Voc is 500VDC.
I verified with the installer and they are sure the panels were wired in series. I see only 2 wires coming down from the roof going into the Inverter. How do I go about testing if there is a measurement error?
Battery charging current during 2000W periods vary from 24A to 30A with one time showing 16A.
Not sure how to tell if batteries were almost full. Inverter says SOC was around 50% or 53.2V.
If load goes up, I don't see PV wattage go up but instead battery kicks in.

 

[zolee]

Hi Bud, thank you for your response.

I have an MPP Solar 5048GK. Max Solar Voltage or Voc is 500VDC.
I verified with the installer and they are sure the panels were wired in series. I see only 2 wires coming down from the roof going into the Inverter. How do I go about testing if there is a measurement error?
Battery charging current during 2000W periods vary from 24A to 30A with one time showing 16A.
Not sure how to tell if batteries were almost full. Inverter says SOC was around 50% or 53.2V.
If load goes up, I don't see PV wattage go up but instead battery kicks in.

You are dangerously close to the maximum Voc of the inverter. I would not connect those panels to that inverter in 10S string.
Very important variable is your minimum outdoor temperature in Celsius. If it come close or below +10°C at any time the panels where illuminated, there is a good chance your inverter is toast.

 

[mrzed001]

Hi Bud, thank you for your response.

I have an MPP Solar 5048GK. Max Solar Voltage or Voc is 500VDC.
I verified with the installer and they are sure the panels were wired in series. I see only 2 wires coming down from the roof going into the Inverter. How do I go about testing if there is a measurement error?
Battery charging current during 2000W periods vary from 24A to 30A with one time showing 16A.
Not sure how to tell if batteries were almost full. Inverter says SOC was around 50% or 53.2V.
If load goes up, I don't see PV wattage go up but instead battery kicks in.

Yep it is dangerously close to 500Voc.
I strongly suggest to remove 1 panel from the string. It is better if you do not go even near 450Voc with these inverters.
If temperature goes below 22Celsius is a sunny day, it will reach 500Voc ... and then your inverter's MPPT will burn out.

Do you have shading? Tree or something ?
This 10s string would give you at least 400Vmpp
Did you check the string Voc with a multimeter ?

 

[benjieg]

You are dangerously close to the maximum Voc of the inverter. I would not connect those panels to that inverter in 10S string.
Very important variable is your minimum outdoor temperature in Celsius. If it come close or below +10°C at any time the panels where illuminated, there is a good chance your inverter is toast.

New info. Installer confirmed that panels are connected in 2 parallel strings of 5. So I'm now thinking that I should be seeing total current between 1x to 2x the Imp. But I'm only seeing a max of 1 x Imp. Should I be seeing much higher current? Panels are well positioned with no shadows.

 

[mrzed001]

New info. Installer confirmed that panels are connected in 2 parallel strings of 5. So I'm now thinking that I should be seeing total current between 1x to 2x the Imp. But I'm only seeing a max of 1 x Imp. Should I be seeing much higher current? Panels are well positioned with no shadows.

Well this is not ideal too
5 panel is only about 5x41 = 205V.
These inverters only really start to work on 180-200V.
And the ideal is 320Vmpp for them.

So I would start first with a 8s (8 in series) configuration.

 

[Maitake]

I just looked at the datasheet.
There is no Imax listed for the mppt which indicates to me it's a weak point.
Bet you a dollar you are hitting MPPT current limit because of the low voltage from the panels.
Previous answer of 8s panel configuration is a good starting point.
Seems you may have been sold mis-matched array-inverter combo.

 

[zolee]

Well, the paralleling change things.
I'd first disconnect the inverter and measure the voltage on the string cable. You should get the full Voc voltage.
Then I'd check the actual current the panels can deliver but I suggest you leave that to the installer.
Maybe you have a faulty panel somewhere.

If everything is in acceptable ranges I'd check the inverter.

 

[mrzed001]

I just looked at the datasheet.
There is no Imax listed for the mppt which indicates to me it's a weak point.
Bet you a dollar you are hitting MPPT current limit because of the low voltage from the panels.
Previous answer of 8s panel configuration is a good starting point.
Seems you may have been sold mis-matched array-inverter combo.

I think it can take 16 or 20A from solar side.
There is even an example in the manual where they suggest to 8s2p 250W (30Vmpp 8Ampp) panels
So at least 16A (from PV side) it can convert.

 

[benjieg]

I just looked at the datasheet.
There is no Imax listed for the mppt which indicates to me it's a weak point.
Bet you a dollar you are hitting MPPT current limit because of the low voltage from the panels.
Previous answer of 8s panel configuration is a good starting point.
Seems you may have been sold mis-matched array-inverter combo.

Here is the label on the Inverter showing the numbers for your reference. Do you still suspect a mismatch?

 

[benjieg]

I think it can take 16 or 20A from solar side.
There is even an example in the manual where they suggest to 8s2p 250W (30Vmpp 8Ampp) panels
So at least 16A (from PV side) it can convert.

So far I'm seeing max 30A PV charging current. Does this help?

 

[benjieg]

Well, the paralleling change things.
I'd first disconnect the inverter and measure the voltage on the string cable. You should get the full Voc voltage.
Then I'd check the actual current the panels can deliver but I suggest you leave that to the installer.
Maybe you have a faulty panel somewhere.

If everything is in acceptable ranges I'd check the inverter.

I haven't tried testing each string since they are joined by a Y-connector on the roof and I can't get to that.
On the breaker side, I have measure a current of 11A and a voltage of 187V (with load) and 229V (open breaker).

 

[mrzed001]

So far I'm seeing max 30A PV charging current. Does this help?

It helps

So 30A on the PV side? Then there is max 160Vmpp on the PV string.
It is at least 3 parallel PV string, so about 5s3p or 5s4p ?
Never tried a setup like this.
What is your experience with it? The PV V is not too low for this inverter ? (the ideal is 320Vmpp)

 

[benjieg]

It helps

So 30A on the PV side? Then there is max 160Vmpp on the PV string.
It is at least 3 parallel PV string, so about 5s3p or 5s4p ?
Never tried a setup like this.
What is your experience with it? The PV V is not too low for this inverter ? (the ideal is 320Vmpp)

Sorry I wasn't specific. I'm seeing 30A battery charging current and 11A PV current.
I have 450W panels is 5s2p. They operate around the 180V range with 11A PV current. So I'm really getting just 2KW and trying to figure out how I can get close to 4500W since I have that much panel power.

Your previous reply suggest and 8s setup instead of 5s2p to get to the ideal 320V range. Do you think that setup would be better?

 

[wattmatters]

One string is not connected. Get the connections checked.

 

[zolee]

Sorry I wasn't specific. I'm seeing 30A battery charging current and 11A PV current.

Did you changed the default maximum charge current? (30A).

I have 450W panels is 5s2p. They operate around the 180V range with 11A PV current.

That's correct for 5s. The second string is not connected. Check that as soon as possible, either the cable is dangling in the breeze, or is the connector burning off the power.

 

[mrzed001]

Sorry I wasn't specific. I'm seeing 30A battery charging current and 11A PV current.
I have 450W panels is 5s2p. They operate around the 180V range with 11A PV current. So I'm really getting just 2KW and trying to figure out how I can get close to 4500W since I have that much panel power.

Your previous reply suggest and 8s setup instead of 5s2p to get to the ideal 320V range. Do you think that setup would be better?

Definitely would be better in 8s (9s would be too much Voc in cold)
This was the reason I asked I saw more 5s config where the production was low (too low Vmpp ... really it start above 200Vmpp).

If you have place for 4-6 more panels then you can use it in 7s2p or 8s2p.
Or you can connect 8s to the inverter and the remaining 2 panels you can connect to an MPPT charger ... and charge the same battery with it

 

[benjieg]

Did you changed the default maximum charge current? (30A).

That's correct for 5s. The second string is not connected. Check that as soon as possible, either the cable is dangling in the breeze, or is the connector burning off the power.

The maximum charging current setting is 60A. I've never really gotten beyond 30A battery charging using PV.

 

[benjieg]

Definitely would be better in 8s (9s would be too much Voc in cold)
This was the reason I asked I saw more 5s config where the production was low (too low Vmpp ... really it start above 200Vmpp).

If you have place for 4-6 more panels then you can use it in 7s2p or 8s2p.
Or you can connect 8s to the inverter and the remaining 2 panels you can connect to an MPPT charger ... and charge the same battery with it

I've actually asked the installer about adding 1 or 2 more panels to the strings. But they said it would go being the max power of the Inverter which is 5kW.

I like this idea because it looks like a cleaner and simpler modification.