Weird Junction Box. How Do I Use It?

[jmsheldon]

I got a junction box that came with my solar cells and it doesn't show how to use it correctly. Could you please show me how? I have a few pictures of it so that you can see what I mean. It has a positive and negative sign but the diode goes from one of those to the other.

[inetdog]

I got a junction box that came with my solar cells and it doesn't show how to use it correctly. Could you please show me how? I have a few pictures of it so that you can see what I mean. It has a positive and negative sign but the diode goes from one of those to the other.

Nothing strange about that. The diode is referred to as a bypass diode. Its purpose is to allow current to be driven past the panel if it is shaded while other panels in series with it are not shaded. When the panel is illuminated, the voltage from it will be opposite to the conducting direction of the diode and no current will flow through it.

It will potentially avoid forward breakdown damage to the panel and will also allow the series string to still produce power even if one panel is completely shaded.

For large panels, the cells are grouped into two or more strings, each of which has its own connection to the J-box and its own bypass diode. It looks like this kit is a fairly low wattage panel.

Connect the + end of your string of cells to the + screw and the - end to the - screw inside the box. The wiring to the load will be connected to the two connectors which are outside the box.

[jmsheldon]

wiring it

Nothing strange about that. The diode is referred to as a bypass diode. Its purpose is to allow current to be driven past the panel if it is shaded while other panels in series with it are not shaded. When the panel is illuminated, the voltage from it will be opposite to the conducting direction of the diode and no current will flow through it.

It will potentially avoid forward breakdown damage to the panel and will also allow the series string to still produce power even if one panel is completely shaded.

For large panels, the cells are grouped into two or more strings, each of which has its own connection to the J-box and its own bypass diode. It looks like this kit is a fairly low wattage panel.

Connect the + end of your string of cells to the + screw and the - end to the - screw inside the box. The wiring to the load will be connected to the two connectors which are outside the box.

Ok. I got what you said. I just don't understand where the wires go in and out of the junction box? Do they come in through the back and then go out through the ports marked positive and negative?

[inetdog]

Ok. I got what you said. I just don't understand where the wires go in and out of the junction box? Do they come in through the back and then go out through the ports marked positive and negative?

Yes. With the box mounted onto the panel, the bus wires/foils will typically come in through the slots in the back.

[jmsheldon]

done

Yes. With the box mounted onto the panel, the bus wires/foils will typically come in through the slots in the back.

Attached is an image of what I did. Is it correct?

Thanks.

[inetdog]

Attached is an image of what I did. Is it correct?

Thanks.

Electrically it looks correct. I can't make any comments about it mechanically because I do not know how you are attaching the j-box to the panel.

And I will just take your word for it that you have the polarity correct.

[jmsheldon]

testing it tomorrow

Electrically it looks correct. I can't make any comments about it mechanically because I do not know how you are attaching the j-box to the panel.

And I will just take your word for it that you have the polarity correct.

I definitely connected the positive to positive and negative to negative. I connected the junction box to the panel from the bus wires, which worked before I put on the junction box.


I will try it out tomorrow morning and tell you if it works or not.

[jmsheldon]

it works

Ok. I tried out my solar panel with the junction box connected. It works well. The panel was cranking out about 50 watts in the winter sun. Thank you for your help.

Is there any way I can get more from it?

It is rated at 72 watts but It was producing 14.5 volts and 3.35 amps.

[inetdog]

Ok. I tried out my solar panel with the junction box connected. It works well. The panel was cranking out about 50 watts in the winter sun. Thank you for your help.

Is there any way I can get more from it?

It is rated at 72 watts but It was producing 14.5 volts and 3.35 amps.

You could start by reading post #25 in this thread.

[jmsheldon]

You could start by reading post #25 in this thread.

It's a little late to test all of my cells since the panel is encapsulated already. I did test each array of cells before I encapsulated them and all four of them showed the same amount of voltage and amperage.