NEWB - New solar panels only measuring 0.5A

[txhackertracker]

i am new to the forum and new to solar, so forgive me for such an elementary question. I wanted to dip my toes in the water and build a solar powered water pumping system to begin with. I purchased 2x 18V 100 watt panels... i was expecting 5A each. However, in full sun angled to minimize shadow, my measurements appear off by a factor of 10x. Can anyone tell me what am I doing wrong? Did I get 2 bad panels? Am I measuring wrong with my multimeter? If it matters, I measured both panels and the voltage/amps are within hundredths of a decimal point difference. Pictures shown below to help diagnose. Thank you in advance!!!


SPECS (from the sticker on the back of the panel)


PANELS AS SET FOR TESTING - Zero shade. Angled to minimize shadow (e.g. directly facing the sun).


VOLTS - Measured 19V. Specs show 18V.


AMPS. <- Here is where i think i have a problem. Notice it is only 0.5A - NOT 5A.

 

[cs1234]

I believe they have to have something putting/pulling a load on them to measure any significant amperage. You need to hook them up to a charge controller and a battery that needs a charge, or some other load.

A multimeter is not going to put a load on them, and the multimeter has to be connected in the circuit with the load to read the amps being drawn.

 

[Mattb4]

You need to move your red lead to the 10a jack. Make sure you select the correct amp scale (A) and not one of the micro amp one.
BTW: although you will get a amp readout it will not give you wattage. For that you need to load your panel. When you read voltage VOC according to your panel is 22.28 so your reading is a tad low but not out of line.

 

[tinyt]

With the DMM shown, you need to move the test lead red plug to the 10A socket. You probably will need a load to measure panel current. I am not sure if it is safe to short circuit the panel for the short circuit current reading. Edit: Mattb4 is faster than me.

 

[cs1234]

You need to move your red lead to the 10a jack. Make sure you select the correct amp scale (A) and not one of the micro amp one.
BTW: although you will get a amp readout it will not give you wattage. For that you need to load your panel. When you read voltage VOC according to your panel is 22.28 so your reading is a tad low but not out of line.

The multimeter would have to be in line in the circuit to get an amp reading, and it would have to be under load from something, wouldn't it?

 

[txhackertracker]

PROBLEM SOLVED ALREADY

DOH!!! I am an even greener newb than advertised. I just watched a YouTube video and determined that I was measuring Amps wrong with my multimeter. Notice the 2 below:

WRONG - Notice where the red probe is connected



RIGHT - Connected my multimeter correctly- moved the red probe to the correct place.


Now Amps are measuring as expected. Hopefully, this can help someone else.

Final (and different) question - Specs show open voltage at 22V. Panel is an 18V panel. I measured both panels at 19.x volts. Is that within the limits of acceptable tolerances for the specs of the panel?

 

[txhackertracker]

Thanks guys for the amazingly quick, helpful and accurate answers!

 

[txhackertracker]

With the DMM shown, you need to move the test lead red plug to the 10A socket. You probably will need a load to measure panel current. I am not sure if it is safe to short circuit the panel for the short circuit current reading. Edit: Mattb4 is faster than me.

Thanks - that was my issue!

 

[cs1234]

Edit: Mattb4 is faster than me.

Faster and more accurate than me.

 

[cs1234]

On the plus side, it appears to be ok to short circuit the panel to test for amperage.. at least for a short duration, on a panel under 10 amps, on a multimeter that can safely do 10 amps.

 

[Mattb4]

The multimeter would have to be in line in the circuit to get an amp reading, and it would have to be under load from something, wouldn't it?

In this case the load is supplied by the MM. However you do not know what the voltage drops to so you can not calculate watts. people think that they have a watt reading because after getting an amp reading they change the leads on the MM and measure volts. Well at that point you have no amp reading.

So to calculate if the panels is delivering watts you must load it and use either a DC clampon meter or shunt to measure.

It is hard to keep in mind but amps are rather meaningless without volts.

 

[cs1234]

Final (and different) question - Specs show open voltage at 22V. Panel is an 18V panel. I measured both panels at 19.x volts. Is that within the limits of acceptable tolerances for the specs of the panel?

Though I didn't catch you using the multimeter wrong, I would say that yes, that's within acceptable range for the panel doing it's own thing with no charge controller driving it.

 

[Mattb4]

Faster and more accurate than me.

I don't know about that. I type with one thumb and two fingers. As to be accurate. I just hope for a 50% rating.

 

[cs1234]

In this case the load is supplied by the MM. However you do not know what the voltage drops to so you can not calculate watts. people think that they have a watt reading because after getting an amp reading they change the leads on the MM and measure volts. Well at that point you have no amp reading.

So to calculate if the panels is delivering watts you must load it and use either a DC clampon meter or shunt to measure.

It is hard to keep in mind but amps are rather meaningless without volts.

Or a second multimeter reading the volts at the same time the other one is reading the amps?

 

[tinyt]

I wish I can afford one like this.

 

[cs1234]

I wish I can afford one like this.

Would be handy if testing a bunch of panels. Kind of a unitasker though if you don't have a bunch of panels to test. Exactly the kind of tool I would buy because it's neat, and find reasons to use it on my panels I already own.