Solar Panel Polarity?

[Richard10002]

How can you tell what is the polarity of a Solar Panel. I have a 100W panel with 5m cables with solar connectors on the ends, one male, one female. Is there a rule for the connectors, e.g female = +ve?

I've taken the cover off where the cables exit the panel, but no clues there:

Many thanks

Richard

 

[neilf39]

The white stripe on the diode is the +ve side so on the right in the photo.

 

[Richard10002]

Thanks for that.... Quite amazing what people here know!

As a matter of interest, what are the two diodes doing? They seem to be connected across the +ve and -ve. I would have thought they would be in line with the +ve or -ve, or both, to stop current flowing the wrong way.

 

[VicS]

Thanks for that.... Quite amazing what people here know!

As a matter of interest, what are the two diodes doing? They seem to be connected across the +ve and -ve. I would have thought they would be in line with the +ve or -ve, or both, to stop current flowing the wrong way.

By-pass diodes ??

 

[nimbusgb]

I wouldn't go wiring up anything capable of delivering 8 amps or more without a decent test meter.

And if you have a test meter you could find out which was positive without taking the covers off the junction box

 

[SAMYL]

Stick the cable ends into the cut surface of a potatoe. The area around one will go black but I can't remember which one.

I'm sure some clever eejit will come up with the correct answer.

 

[nigelmercier]

what are the two diodes doing? They seem to be connected across the +ve and -ve. I would have thought they would be in line with the +ve or -ve, or both, to stop current flowing the wrong way.

Indeed they should, to stop the panel from discharging the battery when there is no sun. You need to get a volt meter on this to check.

 

[Richard10002]

Indeed they should, to stop the panel from discharging the battery when there is no sun. You need to get a volt meter on this to check.

The panel is still in its box... Just trying to make sure I know what I'm doing when I get around to fitting it.

What should I be checking with the volt meter? I guess that there is no current flowing from the battery to the panel when it's dark?

 

[VicS]

The panel is still in its box... Just trying to make sure I know what I'm doing when I get around to fitting it.

What should I be checking with the volt meter? I guess that there is no current flowing from the battery to the panel when it's dark?

The diodes do not appear to be blocking diodes to prevent discharge from the battery through the panel , which is why I suggested they may be bypass diodes

Function of diodes expalined here

Presumably a panel of that power will be connected via a regulator. No additional blocking diode will be required. The function will be included in the regulator circuit.

Check the polarity if you wish by using a voltmeter, or the cut potato method.

Connect the panel to the battery via the regulator following the instructions for wiring the regulator.

Confirm the lack of discharge through the panel at night if you feel so inclined

 

[Richard10002]

It will be going through a PWM controller which can handle up to 10A. I think i understand enough now. All I need to do is check the polarity, get wired up, and start receiving free power

Thanks to all

 

[ex-Gladys]

try and keep the panel out of direct light whilst you are connecting up. I was advised panels don't like producing open voltage

 

[nigelmercier]

The diodes do not appear to be blocking diodes to prevent discharge from the battery through the panel , which is why I suggested they may be bypass diodes ...

Indeed they may be. But if there is any doubt, it needs to be checked, as any assumption could cause a polarity inversion.
No boat owner should be without a simple multimeter, when they can be bought from under a tenner.

 

[VicS]

Indeed they may be. But if there is any doubt, it needs to be checked, as any assumption could cause a polarity inversion.
No boat owner should be without a simple multimeter, when they can be bought from under a tenner.

It does not matter what they are.
The panel has been supplied with 5m leads
The instructions should be adequate to enable it to be connected up without investigating the electronics of the terminal box.

The instructions for wiring the regulator should also be followed. Some, it seems, require the battery to be connected before the solar panel.

 

[NOHOH]

Nobody....

....has told you how to do it...apart from with a potato........

Get a digital multimeter......set the dial to something like V25.....and put the red +ve probe on the left output contact in the picture....and the black one on the other.......You should get a number on the meter display..... If the number is preceded by a -negative sign.....then the polarity is the other way round.....dead easy

 

[nigelmercier]

The instructions should be adequate to enable it to be connected up without investigating the electronics of the terminal box...

I quite agree, but i thought the OP had a reason to ask.

 

[wytco0]

try and keep the panel out of direct light whilst you are connecting up. I was advised panels don't like producing open voltage

I don't think that's correct a PV Phd researcher I know tells me that that they are fine open.

 

[noelex]

I don't think that's correct a PV Phd researcher I know tells me that that they are fine open.

Yes if this was a problem there would be trouble with every solar regulator. They effectively disconect the panel.
Take some precautions when wiring them up however arcs and sparking are not good for DC connections and can be dangerous around a charging battery.

 

[cimo]

The white stripe on the diode is the +ve side so on the right in the photo.

+1.
The diodes cap (cutoff) the maximum output volyage (Vmax in the panels data sheet?).

Your fitting instructions will most likely recommend adding an additional diode in series (to prevent discharge) if not using a regulator.

 

[VicS]

The diodes cap (cutoff) the maximum output volyage (Vmax in the panels data sheet?).

Do they?
Are you sure ?

 

[cimo]

Do they?
Are you sure ?

my spelling badly needs attention - maximum output voltage, not volyage.

Vmax? - read as open circuit voltage or Voc (previous post editied).

These are Zener Clamps unless I'm mistaken.