Trying to Test 4 Panel Series Array with Multimeter - Need Advice

[Ozzymandius]

I have an array of 4 x Newpowa 210W panels connected in series. Each panel rates 12.60A, 17.52 Vmp(V), 20.52 Voc(V).

The series panel array in my backyard is connected via some extension cables to a Hysolis Apollo 5K generator in my garage, which powers and backs up my freezer full of meat. The problem is that the Hysolis is not seeing any solar input, even in full sun. So for now the Hysolis is only pulling power from grid AC. So I need to troubleshoot the cables and panels using a multimeter and have a few questions, as I am a total newbie when it comes to electrical testing.

I think the cables are likely bad as I had crimped some ends myself but I need to test to be sure.

I was thinking of buying one of these specialty solar multimeters for testing (NO affiliate link):

Amazon.com

But the above is only rated to 60V, so if I test the cable ends (80V due to series array), would it blow the meter?

So then I was looking at a standard clamp multimeter that is rated to 600V, like this one (again, no affiliate link):

https://www.amazon.com/dp/B09H2JCXZP

Would the above work if I test the cable ends with the multimeter leads? Should I expect a large spark when the leads insert into the cable ends? Or is there any easier way to troubleshoot my problem, perhaps with a dirt cheap multimeter or no multimeter at all?

All I am trying to determine is if I am getting any power/current out of the cable ends. If not, I would then go to the solar array itself and test the positive and negative originating cables of the array in the same way. If the array itself is outputting, then the culprit would clearly be the extension cables (easy fix, just replace 'em).

 

[timselectric]

Use a multimeter to check the voltage.
This will determine if you have a lost connection.
Be careful, 80vdc will hurt.

 

[ohmboy]

But the above is only rated to 60V, so if I test the cable ends (80V due to series array), would it blow the meter?

All I am trying to determine is if I am getting any power/current out of the cable ends. If not, I would then go to the solar array itself and test the positive and negative originating cables of the array in the same way. If the array itself is outputting, then the culprit would clearly be the extension cables (easy fix, just replace 'em).

If the meter blows, then you have current but I'd get one rated for higher voltage.

 

[Bop]

You don't need a fancy clamp multimeter like that to test your panels, any cheap meter with a 20A DC current range will do...
just as an example https://www.amazon.com/Multimeter meter with 20A DC current range- much cheaper than the clamp one lol
(just be aware many of the really cheap ones only have a 10A DC current range- these will probably blow a fuse on your panels, so check it has that 20A range!!!)

You can do a volts test on each panel individually (unplug it and put the probes in the panels leads- no need to worry about polarity with a digital meter), or by swapping the red lead to the 20A dc current socket and swapping to that range on the knob, measure its current output too (might be a slight spark when you put the lead in doing this- thats normal and OK)

Or the entire string at once (start at the panels, and work back towards the charge controller doing the volts and current test each time (remembering to put the red lead in the appropriate socket!!!)- you can have volts, but no/very low current if you have a high resistance joint in the cable somewhere- so don't always trust the volts reading!!!- many a person has been tricked by the 'volts there' but no current of a high resistance joint lol

 

[Ozzymandius]

Thanks, guys. Looks like Bop's suggest of a cheap 20A DC multimeter should do the trick.

The one Bop suggested should be good up to 20A/250V, which should be safe enough to test the entire 4-panel series string without blowing up the meter.

I will mentally prepare myself for a significant spark though when plugging in the leads!

 

[Hedges]

Checking voltage will not produce any sparks.

Checking current means shorting out the array, will produce an arc and burn the probe tips. I've done that with a suitably rated knife switch (and I used a clamp ammeter not probing.)
You should not need to check current, just voltage. If voltage is applied to inverter and doesn't plunge toward zero when inverter tries to draw from PV, that's all you need to know.
I was measuring current to identify damaged panels, after seeing low (not zero) power & current.

Check voltage with PV string disconnected from inverter, and check again with it connected to inverter.
Sometimes array is wired backwards, and if inverter has reverse-polarity clamping diode you will see about 2V.

Remember that once you stick test lead on PV circuit, other test lead is electrically hot.

Maybe that cheap $30 will serve you well enough. I bought a cheap $100 Harbor Freight Ames 1000A DC clamp meter. That can resolve down to 0.010A to compare parallel PV strings and automotive battery cranking current.

 

[Ozzymandius]

Checking voltage will not produce any sparks.

Checking current means shorting out the array, will produce an arc and burn the probe tips. I've done that with a suitably rated knife switch (and I used a clamp ammeter not probing.)
You should not need to check current, just voltage. If voltage is applied to inverter and doesn't plunge toward zero when inverter tries to draw from PV, that's all you need to know.
I was measuring current to identify damaged panels, after seeing low (not zero) power & current.

Check voltage with PV string disconnected from inverter, and check again with it connected to inverter.
Sometimes array is wired backwards, and if inverter has reverse-polarity clamping diode you will see about 2V.

Remember that once you stick test lead on PV circuit, other test lead is electrically hot.

Maybe that cheap $30 will serve you well enough. I bought a cheap $100 Harbor Freight Ames 1000A DC clamp meter. That can resolve down to 0.010A to compare parallel PV strings and automotive battery cranking current.

"Check voltage with PV string disconnected from inverter, and check again with it connected to inverter."

When it is connected to inverter, how would I check voltage as the cheap meter I just ordered is not a clamp meter?

Sorry for the dumb question but as mentioned, I am a total newbie at electrical testing.

 

[Hedges]

As a newbie, wear rubber shoes, don't lean against or otherwise touch any metal, keep one hand in your pocket and use other hand to hold both test leads and put the metal tips in contact with the circuit conductors being measured. This reduces the chance of an electric shock passing through your body (that's something experienced guys like me have experienced, and we don't want you to have that happen.)

With any PV switch or breaker switched off, probe the terminals where PV leads come in to the equipment (external breaker, or terminals of inverter if it has internal switch).
Turn on switch/breaker and check again. If voltage previously Voc now drops to near zero, there is either a short or PV string has high resistance/near open.

Clamp meter is only to measure current without interrupting circuit to make electrical connection.
Most clamp meters, and your cheap meter, have test leads for voltage. That you can do without disconnecting anything.

Don't plug leads into "Amps" terminal, just "Volts" and "Common" or something like that.
Set to DC Volts, suitable range.
Probe the screw terminal or other exposed contacts.

 

[OzSolar]

Sorry for the dumb question but as mentioned, I am a total newbie at electrical testing.

I'd suggest YouTube. Tons of great "how to use a DVM (or digital volt meter)" videos there.

2nd suggestion is that at your skill level I'd wholeheartedly steer you away from trying to test current by running it through your DVM. Additionally, it's super easy to forget to put your leads back the voltage port and there goes your fuse.

You need a DC clamp on meter. I've got several of this ~$40 one and it does great.

KAIWEETS KC604 Digital Clamp Meter

This clamp meter can accurately measure AC/DC current, AC/DC voltage, temperature (thermocouple included), NCV, capacitance, frequency, resistance, continuity and diode. Good help for troubleshooting the household solar system, automotive and industrial electrical issues, perfect for...

kaiweets.com

 

[Bop]

Clamp meters have their place, but are extremely expensive for what tests Ozimandius has to do, and is totally unnecessary...

A simple voltage and short circuit current test will reveal any issues (the clamp meter depends on the battery bank being flat enough to get the panels output up to their maximum), the short circuit output test connected directly across the panel/array will have them putting out their maximum possible current output (allowing for the weather conditions) and will reveal a high resistance connection that will be hidden in the voltage testing by the meters high impedance...

It also allows 'step by step' testing of all the various connections and cables along the way- something the clamp meter can't do (at least while being used as a clamp meter- and indeed the $60 one on that Kaiweets site (the cheapest) has no provision for measuring current at all except by the clamp!!!)- if the circuit is faulty, it has to go back to being a 'normal' plug in meter on the high current range to trace the fault- so no point in even having the clamp at that point...

For Ozi- this test for high resistance joints is only good on the panels themselves- because they are what is known as a 'current limited source (the Isc shown on the specifications label is the MAXIMUM it is capable of putting out), so putting the meter directly across it on the current range is quite safe, and won't damage the meter or the panels...

Doing it on a battery will result in a blown fuse in the meter however, as the battery bank is not (practically speaking) a current limited power source!!!

 

[MichaelK]

Yes, the OP can get the answers he needs with a 12$ multimeter, but clamps really are something that every off-grid enthusiast (OGE) should eventually have.

Here is one on Ebay that will work.


Getting back to the clamp meter, it is a MUCH safer way to check the amount of amps flowing. A cheap meter like the one illustrated above will short out if you take your time collecting your readings.

The proper clamp I think that every OGE needs is something like to Uni-T 216C, which I myself bought, and recommend to others. It can read both AC, and DC amps, along with motor-starting inrush current, which was invaluable for designing my system to run my well-pump.

 

[Bop]

Yes, the OP can get the answers he needs with a 12$ multimeter, but clamps really are something that every off-grid enthusiast (OGE) should eventually have.

Here is one on Ebay that will work.
View attachment 244414

Getting back to the clamp meter, it is a MUCH safer way to check the amount of amps flowing. A cheap meter like the one illustrated above will short out if you take your time collecting your readings.

The proper clamp I think that every OGE needs is something like to Uni-T 216C, which I myself bought, and recommend to others. It can read both AC, and DC amps, along with motor-starting inrush current, which was invaluable for designing my system to run my well-pump.

View attachment 244413

I disagree, the clamp meters themselves have their own limitations, and the number of times I have used mine (bought back when the 'cheap and nasty' ones were still in the several hundred dollar range), they really aren't that useful, nor in most cases capable of testing for the most common faults..
With a fault condition already existing, we already know the circuit doesn't work, and they can't tell where the issue is... (thats where the 'short circuit' test comes into play with a high resistance joint somewhere in the circuit)- impossible to test in a PV solar circuit without disconnecting the plugs as there is no 'easy access to the connections' without unplugging them, and that lowers the current enough that a measurement using the volts range becomes meaningless when on the 'wrong side' of the fault... the voltage still remains high when measured by the voltage range on the meter, but drops under load... but that can't be done unless you put an artificial load on the circuit while its being measured- which is ironically exactly what you are doing by using the DC current range with a conventional multimeter- using the low resistance of the meters internal shunt resistor as that load lol

About the only time I ever used mine in the last couple of decades, was to verify that the existing meters themselves were actually accurate (more common back in the days of 'analogue dial meters') or to check on alternators that they hadn't 'dropped a phase' in cars , but as an actual fault finding tool, (especially in modern PV systems where 'ye old dial meters' have practically disappeared), they really are a poor substitute...

They aren't even that useful for determining peak currents unless they have a 'hold measurement' feature as neither the display, nor the human eye, is fast enough to be able to catch and display the surge peak values which can come and go in a few hundred milliseconds...

 

[MichaelK]

They aren't even that useful for determining peak currents unless they have a 'hold measurement' feature as neither the display, nor the human eye, is fast enough to be able to catch and display the surge peak values which can come and go in a few hundred milliseconds...

Please try to pay attention. I specifically mentioned inrush, which is what happens in the first few hundred milliseconds.

 

[Bop]

Please try to pay attention. I specifically mentioned inrush, which is what happens in the first few hundred milliseconds.

Please try to pay attention yourself (and can the snark)- unless your meter has a 'hold reading' feature (most don't, especially in the cheap end of the market) you can't SEE the actual peak inrush current value... its over too quickly...

 

[OzSolar]

The problem is that the Hysolis is not seeing any solar input, even in full sun.

Why aren't we asking the most basic of questions? Arguing the finer points if one needs a DC clamp on meter or suggesting that a dangerously laughable DVM that is rated to run 20 amps through it (the only one in existence that I've ever seen) is the only thing you need is missing the point. By the way, never attempt any electrical trouble shooting without at least two meters that you trust and know how to use. Why aren't we offering those sorts of tips?

Side note: One really does need to have a DC clamp on meter, it's just irresponsible to suggest you don't.

Anyway... back to actually trying to help the OP. A large number of new comers have never been told that that the entire array needs to be in full sun and at an ideal angle for it produce anywhere near it's rated power. Maybe we could start there?

Perhaps thier "solar generator" is not getting enough or too much voltage to work properly?

Let's get those answers and go from there.

 

[Bop]

Why aren't we asking the most basic of questions? Arguing the finer points if one needs a DC clamp on meter or suggesting that a dangerously laughable DVM that is rated to run 20 amps through it (the only one in existence that I've ever seen) is the only thing you need is missing the point. By the way, never attempt any electrical trouble shooting without at least two meters that you trust and know how to use. Why aren't we offering those sorts of tips?

Side note: One really does need to have a DC clamp on meter, it's just irresponsible to suggest you don't.

Anyway... back to actually trying to help the OP. A large number of new comers have never been told that that the entire array needs to be in full sun and at an ideal angle for it produce anywhere near it's rated power. Maybe we could start there?

Perhaps thier "solar generator" is not getting enough or too much voltage to work properly?

Let's get those answers and go from there.

I have several here (as a working tech, I have quite the collection of gear) and only the cheapest of the cheapies (picked up at a local hardware store because I needed one while on holidays, and stupid me didn't pack all my tools for the trip...) only had a 10A high current range...

I trained as an apprentice on DC levels 99.999% of people here have never dreamed of (1600vDC at 20kA plus, as an electrical fitter on the state railways, dealing with electric loco's lol) and sent much of my working life dealing with solar in one form or another (offgrid installs since the 1980's, gridties since 2004, now basically retired and living the Aussie 'bush' dream lol) and despite owning TWO clamp meters (one was over $300 when new- and that was just for an external clamp that had to be plugged into an existing multimeter) I have rarely used them that much (and less and less as the years rolled by, their most useful aspect being negated by most equipment having onboard metering now...
And with that...
OK- off to ignore you go...
(can't be civil, then... u...)

 

[OzSolar]

OK- off to ignore you go...

Thank you! Please go away before you get someone hurt.

 

[Bop]

Despite what some other 'people' have been saying, the 'recommended' clampmeter above (the Uni-T) would actually be useless for testing for the fault (as it doesn't have any provision for measuring current except by the clamp meter) and the voltage testing will show no fault present at all (due to the meters high impedance not loading the circuit high enough) while the PV leads are unplugged for testing...

Been installing solar here in Australia for forty years (yes, its been around that long lol), so I KNOW what, and what not, any particular piece of test equipment can do... and own most of it...

So you really need to know what each piece of equipment capabilities and limitations really are (some apparently have no idea)

 

[labeeman]

Get a 200-watt incandescent light bulb even a 100-watt one will do, connect it across the 4 panels if the light glows your panels and connections are OK if not you have a panel and or connection problem.

 

[Bop]

Get a 200-watt incandescent light bulb even a 100-watt one will do, connect it across the 4 panels if the light glows your panels and connections are OK if not you have a panel and or connection problem.

Funnily enough- that was an answer in many cases (automotive guys often have 'two test lights'- ones a LED tester for the 'electronics' circuits (cause they have current limits, and too much current through them can damage the delicate electronics like in the ECU etc) and the other a good old fashioned 'light bulb in a pen' style tester...

versus

(funnily enough I have both of those types- indeed both are those exact same units!!!
(and the metal one is from the 1980's- and they are still making the exact same design today!!!)

 

[ohmboy]

Funnily enough- that was an answer in many cases (automotive guys often have 'two test lights'- ones a LED tester for the 'electronics' circuits (cause they have current limits, and too much current through them can damage the delicate electronics like in the ECU etc) and the other a good old fashioned 'light bulb in a pen' style tester...

View attachment 244676 versus View attachment 244677

(funnily enough I have both of those types- indeed both are those exact same units!!!
(and the metal one is from the 1980's- and they are still making the exact same design today!!!)

The light bulb one was one of our projects in auto shop. Had to drill the plastic handle of a screw driver to the metal part to fit a fuse like bulb. Then just put a wire and spring to complete. Oh, make the screw driver end pointy.