Solar Multimeter Testing

[RolfP]

I am hoping to troubleshoot my solar installation with a multi-meter but am electrically challenged. I put my panel in the sun, connect the MM red to positive and black to negative, set the meter to 50 DC V and get a reading of about 20-ish. To determine amps, I set my meter to 10 amp, switch the red wire to DC10amp and get nothing nada. Am I doing something wrong, or is this expected? See pics below.

[Paul Elliott]

It looks like you're doing it right. If you are just measuring the panel by itself (the panel has a 3A short-circuit current) then the meter should be able to handle it.

But, it's not uncommon for the internal fuse (fuses?) to blow on volt/ammeters, due to inadvertent overcurrents. I've done it myself, by (among other things) trying to measure my battery voltage while forgetting that I still had the meter configured for amps. The blown fuse won't affect the Voltage readings, as it's only in the Amps connection. These fuses can be replaced without too much trouble, if you can find a replacement that is.

I am 90% sure the fuse is your problem.

[RolfP]

Okay, re-checked he fuse, it is good. I have a nice cache of fuses for his meter because I don't know how to use it . . . :-)

[jdazey]

Please keep in mind that I'm absolutely no electrical expert.

Unless you disconnect one of the wires (red) from the panel, the amps are going through the wires instead of the mm. Disconnect the red wire from the panel and place your mm probes on the wire and the terminal so that everything goes through the mm. If the amperage is too high the fuse will blow. That's why dc ammeters normally use a shunt.

[NahanniV]

Looks like you are doing it correctly.

With the panel in some sun:

Try touching the solar panel leads together, there should be a little spark as they touch.

Try a small 12v light-bulb connected to the panel if you have one.

If you see the spark and/or can light the light-bulb look at the meter. Could be a bad fuse holder or broken AMP function.

If no spark or light from bulb, the panel may have a high resistance (bad) connection; That would account for seeing voltage, but not (much) current. In that case, check for a smaller current using the miliamp scale of the meter.

Cheers,
JM.

[Tailwheel]

What Jdazey said!

When it comes to measuring current, the MM needs to be part of the circuit.

No I am not an expert, but I've done this a few times.

Matt


Sent from my iPhone using Cruisers Sailing Forum

[paulajayne]

To measure amps the multimeter need to be inline, part of the circuit.


Amps is a measurement of load/work.

[Paul Elliott]

If Rolf had been measuring around 20V voltage at the panel, and then kept his connections to the panel as-is while he switched to meter to measure amps, then his meter *is* in the circuit and should be reading the panel's short-circuit current.

Yes, perhaps there's a high-resistance connection, which would still show a reasonable voltage but very low amps. I still suspect the fuse (even though Rolf says it's OK), and would try measuring current elsewhere to verify that the meter's OK.

[jeepbluetj]

Originally Posted by Paul Elliott

If Rolf had been measuring around 20V voltage at the panel, and then kept his connections to the panel as-is while he switched to meter to measure amps, then his meter *is* in the circuit and should be reading the panel's short-circuit current.

Yup. The meter (set to measure current) would short out the panel and you should be able to read Isc at that point.

Vote #2 for a blown fuse, or a fried meter. If the panel is putting out voltage, it should be putting out measurable current unless something is horribly wrong.

[travellerw]

Originally Posted by Paul Elliott

If Rolf had been measuring around 20V voltage at the panel, and then kept his connections to the panel as-is while he switched to meter to measure amps, then his meter *is* in the circuit and should be reading the panel's short-circuit current.

Yes, perhaps there's a high-resistance connection, which would still show a reasonable voltage but very low amps. I still suspect the fuse (even though Rolf says it's OK), and would try measuring current elsewhere to verify that the meter's OK.

No his meter is not "in circuit" his meter would be in parallel with the panel. To measure current your meter must be in series. Also the panel MUST be connected to a load (i.e. a battery) or you won't measure anything.

So.. If you have a battery connected to the panel, take the positive wire (coming from the panel) off the battery and connect it to the RED wire on the multimeter. Then take the black wire on the multimeter and touch the positive post on the battery (yes the black wire on positive). The multimeter is now "in circuit" and can measure the current.

[Canibul]

Put another way, there has to be a complete circuit and the meter is part of that complete circuit.

OR you could do something that you will appreciate later and buy a clamp meter.

[senormechanico]

First, make sure panel is not connected to your battery.

If the panel is in the sun and you connect the meter in the amps configuration and still get nothing, it has to be a bad connection either in the meter, wiring or panel.
No load is needed, the meter can be connected directly across it and you should get at least a fair percentage of the short circuit current advertised on the back of the panel.

[Paul Elliott]

While we wait for more feedback from Rolf, let me toss out a few ideas:

The panel is not connected to the battery, because the voltage is measured at 20V. This is a disconnected or unloaded panel. I suppose there could still be a controller connected to a fully-charged battery, but let's assume not.

When you place an ammeter across the panel connections (+ to -) the meter *is* the circuit. The meter is putting a virtual short-circuit load on the panel. Since there is apparently no other load on the panel, the ammeter will show the Isc (short-circuit current) of the panel.

Disconnected panel, volt/ammeter. Can't get much simpler than that. There's either a *very* poor connection, or the meter is broken.

[travellerw]

Originally Posted by Paul Elliott

While we wait for more feedback from Rolf, let me toss out a few ideas:

The panel is not connected to the battery, because the voltage is measured at 20V. This is a disconnected or unloaded panel. I suppose there could still be a controller connected to a fully-charged battery, but let's assume not.

When you place an ammeter across the panel connections (+ to -) the meter *is* the circuit. The meter is putting a virtual short-circuit load on the panel. Since there is apparently no other load on the panel, the ammeter will show the Isc (short-circuit current) of the panel.

Disconnected panel, volt/ammeter. Can't get much simpler than that. There's either a *very* poor connection, or the meter is broken.

Yes sorry... that would be correct! I don't typically test my panels that way as mine are always hooked up.

Just a note. If you are testing panels and your meter has a 10A fuse, you need to be carefull. Theoretically a 150w panel can blow that fuse if you have a battery hooked up and testing in series. On my meter, that means $40 down that drain!

[Canibul]

So, if that's the case, whenever I touch my two probes to live wires I should get sparks at the meter probes as I just shorted the circuit?