No name panel wiring

[trupper]

Got this panel, I believe 200 watts, nothing on it indicating a brand. There are 4 flat contacts sticking out the back, I'm just trying to figure out on how to wire it without burning anything. Any suggestions?

 

[Bud Martin]

Posting good clear pictures will be a great starting point.

 

[OffGridInTheCity]

Posting good clear pictures will be a great starting point.

Agree with @Bud Martin.

Wildly guessing - It might need a 'junction box' - e.g. the black box glued on the back of a panel that connects the tabs (from the cells) thru diodes out to the +/- MC4 connectors like this - https://www.ebay.com/itm/234237556409?hash=item3689a576b9:g:rzwAAOSwqJVhaXwt Panels will have 2 or 3 or 4 tabs, you buy the appropriate Junction box and solder the tabs to the box and check the voltage/amps coming out

 

[trupper]

Apologies, I was sure I attached the images. Will update the post now.

 

[RCinFLA]

Each adjacent two are down and back long row of cells . Two outside tabs are overall panel pos and neg. Should be three bypass diodes, one between each tab wire.

You have to check which outer wires are overall positve and negative lines by voltmeter reading. Normally these tabs go into junction box with bypass diodes. Everything needs to sealed from water/moisture.

72 series cells, 6x12 array. about 37v Vmp, 45.5v Voc. Cannot estimate cell size from picture, but likely about 280-300 watt panel. Each cell should put out Isc of 40-45 mA per square cm of area in cell. Imp about 0.95 x Isc. Likely each cell 8 to 9 amps in full sun.

 

[Bluedog225]

Good to know. I’ve got a couple of broken panels this so fix. Thanks!

 

[trupper]

@RCinFLA thanks so much! Just measured the voltage, from 2 outer tabs 42v, 14v and 28v on second and third tabs. Looks like a 300 watts panel then? Which junction box should I buy then?

 

[RCinFLA]

@RCinFLA thanks so much! Just measured the voltage, from 2 outer tabs 42v, 14v and 28v on second and third tabs. Looks like a 300 watts panel then? Which junction box should I buy then?

Voltage is just based on number of series cells 0.63v Voc per cell, 0.52v Vmp per cell @25 degs C

Current depends on cell size. Measure L X W in centimeters of cell and multiple by 0.042 amps. This will be Isc and Imp is about 0.95 x Isc.

Standard wafer sizes: 15.6 cm x 15.6 cm = 214 cm^2 x 0.043A = 9.2A Isc at full 1000 w/m^2 sun for top quality cells. x0.95 -> Imp = 8.7A.

Other standard wafer sizes:

Size ID	Size mm
M0	156.00
M1	156.75
M2	156.75
M3	158.75
M4	161.70
M5	165.00
M6	166.75
M12	210.00

 

[trupper]

It's exactly 156mm! 8.7amp? How do I figure out which junction box to buy?

 

[OffGridInTheCity]

It's exactly 156mm! 8.7amp? How do I figure out which junction box to buy?

You need the right number of tabs - e.g. a 4 tab connection 'type' in your case AND diodes that can handle the amps.
This one is 4 tab / 9a.. up to 250w - https://www.ebay.com/itm/234237556409?hash=item3689a576b9:g:rzwAAOSwqJVhaXwt
This one is 4 tab / 12a.. up to 320w - https://www.ebay.com/itm/265314873773?hash=item3dc5ffb1ad:g:IVQAAOSw8gdhQlGG

It's OK to use one that has higher amp diodes than you need, just cost a couple more $

 

[RCinFLA]

Don't buy anything with two diodes soldered in parallel.