Measuring Current From Panels

[Solargrow]

Hello Again Folks,
This is one of the most knowledgeable groups of folks around so I'm back with another ridiculous question.
How do I measure the total current my panels are producing if it's over 20 amps? I picked up a clamp meter that reads up to 600a but from what I can tell it only measures active current. So it looks like it's only measuring the current my inverter is drawing, but it's not telling me the total current being produced by the panels. It's a 3s6p system so the current should be maxing somewhere around 50a (probably less since they're used panels). My multimeter tells me the total current being produced but it maxes out at 20a and my growatt inverter only tells me what's being used also.
Am I going to have to get a stationary meter that wires into the system or is there a different tool I might need to invest in?
Thanks again

 

[Don B. Cilly]

You can short-circuit the panel outputs and measure that.
3s probably means high voltage, so be careful, use a circuit breaker or something to do it.
No harm will come from it (to the panels ;·), they'll just "think" they have a 100% efficient SCC.
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[Bud Martin]

Hello Again Folks,
This is one of the most knowledgeable groups of folks around so I'm back with another ridiculous question.
How do I measure the total current my panels are producing if it's over 20 amps? I picked up a clamp meter that reads up to 600a but from what I can tell it only measures active current. So it looks like it's only measuring the current my inverter is drawing, but it's not telling me the total current being produced by the panels. It's a 3s6p system so the current should be maxing somewhere around 50a (probably less since they're used panels). My multimeter tells me the total current being produced but it maxes out at 20a and my growatt inverter only tells me what's being used also.
Am I going to have to get a stationary meter that wires into the system or is there a different tool I might need to invest in?
Thanks again

What is the make and model of the clamp-on meter? Can it measure DC current with the clamp?
"active current." What do you mean by 'active current'? Do mean it can only measure AC current only?

 

[Hedges]

How do I measure the total current my panels are producing if it's over 20 amps? I picked up a clamp meter that reads up to 600a but from what I can tell it only measures active current.

Do you mean AC current? You need an AC/DC clamp meter.

I bought the Harbor Freight 1000A/600A/60A one because it has resolution down to 0.01A. Cost $100.

You can short-circuit the panel outputs and measure that.

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But don't do that while both PV+ and PV- are still connected to input of SCC (ask me how I know this.)

Making/breaking the connection will cause an arc. It can be done with a suitably rated switch/breaker.
It can also be done by covering the panels, or tilting them 90 degrees to the sun. Voltage will still be high and current high enough to be hazardous, but not enough to burn connectors.

While connected to SCC you should be able to read amps, or volts and watts on the display.
Disconnected, Voc and Isc don't tell the entire story. Vmp and Imp can be low. I used a space heater as a resistor to test.

 

[rmaddy]

I'd be really surprised if you solar charge controller can't tell you how many volts and amps are coming in from the panels. Which controller exactly do you have?

 

[Bobert]

I load up my system so I am using more wattage than my panels can produce and use a dc clamp meter on one wire of each serial string I can then add the amperage together to get my total. This of course will only work if you have access to the solar panel wiring. It’s a good way to find if you have an under preforming string.

 

[Hedges]

That's what I bought my clamp ammeter for. I found one disconnected string, and one underperforming.
I then went through that string one panel at a time, measuring performance to find the bad ones.

Measuring PV panel performance

I suppose I could buy a solar panel tester like Will reviewed, but that doesn't feel DIY enough to me. Besides, I'm a cheapskate, and I try to do things in the most difficult (and expensive if the equipment wasn't on hand) way. I'm presently working on an underperforming string of Sharp 165W...

diysolarforum.com

 

[Solargrow]

I'd be really surprised if you solar charge controller can't tell you how many volts and amps are coming in from the panels. Which controller exactly do you have?

It's the spf3000tl lvm and it shows the voltage and current being used. It doesn't tell me how much is being produced (that I know of).

 

[rmaddy]

It's the spf3000tl lvm and it shows the voltage and current being used. It doesn't tell me how much is being produced (that I know of).

What do you mean by the voltage and current being used? Is that the incoming from the panels or the outgoing to the battery?

The incoming voltage and current is what's being produced.

 

[Solargrow]

What is the make and model of the clamp-on meter? Can it measure DC current with the clamp?
"active current." What do you mean by 'active current'? Do mean it can only measure AC current only?

Yeah it's an ac/dc meter. By active current I mean it's only reading the current my inverter is using. I'm referring to that as active current. As opposed to the total current my panels are producing.
So if my panels are producing 45a, but my inverter is only requiring 10a to power the load, the clamp meter will read 10 amps because that's what's actively flowing through the wires. I also want to know the total being produced by they panels however.

 

[Solargrow]

What do you mean by the voltage and current being used? Is that the incoming from the panels or the outgoing to the battery?

The incoming voltage and current is what's being produced.

It does show total voltage being produced but not total current. If it's using 9.3 amps to power the load and charge the battery it's going to read 9.3a from the panels. It will pretty continuously read the full 100v throughout the day but the amperage reading will fluctuate based on the load.

 

[Bud Martin]

Yeah it's an ac/dc meter. By active current I mean it's only reading the current my inverter is using. I'm referring to that as active current. As opposed to the total current my panels are producing.
So if my panels are producing 45a, but my inverter is only requiring 10a to power the load, the clamp meter will read 10 amps because that's what's actively flowing through the wires. I also want to know the total being produced by they panels however.

The 45A is the charging current provide by the SCC to charge the batteries and the loads, so if the inverter is drawing 10A, then the batteries are drawing 35A.
So why can't you not able to put clamp on one of the two PV cable feeding the SCC PV input terminal to see how much current the SCC is drawing from the panel.
What is the PV input Voltage showing on the SCC display?

 

[Solargrow]

The 45A is the charging current provide by the SCC to charge the batteries and the loads, so if the inverter is drawing 10A, then the batteries are drawing 35A.
So why can't you not able to put clamp on one of the two PV cable feeding the SCC PV input terminal to see how much current the SCC is drawing from the panel.
What is the PV input Voltage showing on the SCC display?

No that's not what I'm saying. I can put the clamp on the cable and see what the SCC is drawing. I don't want to know what the inverter is drawing, I want to know what the panels are producing.
What I'm saying is the inverter is pulling 9.3 amps total (7 amps to power the fans and 2.3 amps to charge the batteries). The panels, however, are producing 45 amps or so in the heat of the day. The screen on my inverter reads 9.3a and will always fluctuate according to the load, not the amount of power being produced by the sun. Even the graph in the app shows power used by the inverter, not power produced.

 

[Bud Martin]

No that's not what I'm saying. I can put the clamp on the cable and see what the SCC is drawing. I don't want to know what the inverter is drawing, I want to know what the panels are producing.
What I'm saying is the inverter is pulling 9.3 amps total (7 amps to power the fans and 2.3 amps to charge the batteries). The panels, however, are producing 45 amps or so in the heat of the day. The screen on my inverter reads 9.3a and will always fluctuate according to the load, not the amount of power being produced by the sun. Even the graph in the app shows power used by the inverter, not power produced.

So put the clamp on the PV cable feeding the the SCC to se how much current the system is drawing from the panel, multiply that by the PV input Voltage that is shown on the SCC that I ask for, the result will be the power the system is drawing from the panel, panels do not push power into the system, the system pull the power from the panels as needed.
How do you know that the panels are producing 45A? How did you measure that?

 

[Don B. Cilly]

Well, if you want to know what the panels can produce, as I said, short-circuit them. In the best sun conditions.
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[Solargrow]

So put the clamp on the PV cable feeding the the SCC to se how much current the system is drawing from the panel, multiply that by the PV input Voltage that is shown on the SCC that I ask for, the result will be the power the system is drawing from the panel, panels do not push power into the system, the system pull the power from the panels as needed.
How do you know that the panels are producing 45A? How did you measure that?

I have another 7s2p system that puts out about 230v and 15a in the sun. I know this because when I put my multimeter on the terminals it ALWAYS reads what the panels are producing, regardless of what the inverter is using.
If it's pushing 15a but the inverter is only using 6a, the multimeter will read 15a (giving me the total current produced by the panels) and the clamp meter will read 6a (giving me the current being used by the inverter). After 20a I lose the ability to use the multimeter so I want to know what the alternative is. It's starting to sound like the shirt circuit is about it?

 

[Solargrow]

Well, if you want to know what the panels can produce, as I said, short-circuit them. In the best sun conditions.
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What would short circuiting them look like? What do you mean?

 

[Solargrow]

Well, if you want to know what the panels can produce, as I said, short-circuit them. In the best sun conditions.
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Also, this is basically what my multimeter does, right? But the multimeter only goes up to 20a and the clamps use a different method.

 

[Bud Martin]

I have another 7s2p system that puts out about 230v and 15a in the sun. I know this because when I put my multimeter on the terminals it ALWAYS reads what the panels are producing, regardless of what the inverter is using.
If it's pushing 15a but the inverter is only using 6a, the multimeter will read 15a (giving me the total current produced by the panels) and the clamp meter will read 6a (giving me the current being used by the inverter). After 20a I lose the ability to use the multimeter so I want to know what the alternative is. It's starting to sound like the shirt circuit is about it?

"system that puts out about 230v and 15a" so you are saying you are able to measure the panel current of 15A? 230Vdc of PV Voltage and 15A of current draw from the panels?
Please explain how you go about measuring the 15A, did you remove the PV cable feeding the SCC PV input and put the meter in series with the wire to read the PV current?
PV panels do not PUSH current into the system, the current is being PULLED from the panels by the system.
I think you are confusing the PV panels current with SCC charging current. The SCC take the high Voltage and low current panels and buck convert it down to battery charging Voltage, in your case you have 48VDC system, and higher current.

 

[Don B. Cilly]

Look, it's how SCC (Short Circuit Current) is measured.
If you want to measure the SCC on your panels, you short-circuit them.
Obviously, if you have high voltages, take the appropriate precautions.
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