Need help figuring out solar panel polarity

[smlobx]

Once again I’m coming here with my hat in hand to ask the knowledgeable group an electrical question...

I purchased a 120 volt foldable solar panel from Overland Solar. It has the SAE plug. My thought is that I may need to use it if we are camped for a few days where the existing panels on the roof may be covered by trees and I can set this up in an open area.

https://overlandsolar.com/collections/portable-solar-panels/products/bugout-120-solar-charger


I am trying to figure out how to attach it to my Blue Sky 3000i MPPT controller which has a + and - attachment for the solar panels.

https://sunforgellc.com/solar-boost-3000i/

So my question is how do I determine which wire in the SAE plug is positive and which is negative?

I have called and emailed Overland Solar multiple time in the last 10 days or so but have not received a response...

Thanks!

 

[craig333]

I hope the 120 volt is really a 120 watt panel. A voltmeter is the easy to way to tell.

 

[rando]

Most straight forward way is with a multimeter. Put the voltmeter on the DC volts setting and measure the output from the panel - if it says something like 20V then the red lead is on the positive terminal, if it says -20V then the red lead is on the negative terminal.

 

[smlobx]

I hope the 120 volt is really a 120 watt panel. A voltmeter is the easy to way to tell.

Yes you are correct!
My electrical knowledge wouldn’t fill a thimble...

 

[smlobx]

Most straight forward way is with a multimeter. Put the voltmeter on the DC volts setting and measure the output from the panel - if it says something like 20V then the red lead is on the positive terminal, if it says -20V then the red lead is on the negative terminal.

Thanks Rando..
both leads are black..Here is a better link to the wire I have..

https://overlandsolar.com/collections/accessories-connectors/products/15-foot-sae-to-sae-uv-coated-extension

 

[Vic Harder]

Thanks Rando..
both leads are black..Here is a better link to the wire I have..

https://overlandsolar.com/collections/accessories-connectors/products/15-foot-sae-to-sae-uv-coated-extension

Wire color doesn't matter. Like the guys said, get an inexpensive meter, put the panels in the sun, and stick the meter's probes onto the ends of that wire... determine which way around you have to connect them.. +ve (red) meter wire to which end of the solar panel's output (the shiny protruding side (outy) or the inny ... where the metal bits are protected by the plastic) to get the meter to show a +ve voltage.

Make sense?

 

[smlobx]

Wire color doesn't matter. Like the guys said, get an inexpensive meter, put the panels in the sun, and stick the meter's probes onto the ends of that wire... determine which way around you have to connect them.. +ve (red) meter wire to which end of the solar panel's output (the shiny protruding side (outy) or the inny ... where the metal bits are protected by the plastic) to get the meter to show a +ve voltage.

Make sense?

I had to laugh!
Now you’re explaining it in terms that I can understand..

I’ll try it in a bit....

 

[PaulT]

Get one of these: https://www.harborfreight.com/7-function-digital-multimeter-63759.html?_br_psugg_q=multimeter

Although not what I use for important stuff, it is fine for simple tasks. I keep one in the camper, one in the boat, and another in a tool bag so that I don’t have to guess. Also, no worries if it grows legs. Sometimes, they are on sale for about $3.00

Paul

 

[smlobx]

Okey Dokey!

I think I have it figured out...

Using the “instructions” from you folks I opened the panel up and laid it up against my Jeep. Now it has been somewhat overcast today and the panel was not laid flat and perpendicular to the sun but I was able to determine the polarity of the wires.

At first it was reading about -5.0 A but when I reversed the leads it flipped to 5.0A +/-!
Does that sound about right for a foldable panel in less than perfect conditions?

 

[craig333]

Sure does, Now don't forget to mark them!

 

[PaulT]

5 amps in less than ideal circumstances sounds pretty good when it is rated for 7 amps in ideal circumstances.

Paul

 

[smlobx]

Sure does, Now don't forget to mark them!

absolutely!