"Built In Blocking Diode" wired correctly?

[CaptainBob]

I've bought a cheap 80W solar panel off eBay which has a "built in blocking diode" but looking at the wiring I'm not convinced it's "built in" correctly. Here's a picture of it with the MC4 wires coming out of the bottom of the junction box, and inside the box are two diodes, but they're wired across the wire connections, not in-line with them as I was expecting.

Do I need to install an additional diode in series in the positive output?

Here's the picture...

 

[Barry Jones]

Where is it telling you to connect those wires ?

 

[CaptainBob]

The wires pictured leaving that junction box, downwards in the picture, are the - and + (respectively) supply lines. They terminate with MC4 male and female connectors. I was simply intending to connect those directly into the solar input of my Marlec HRDi regulator.

 

[Barry Jones]

If thats the case, the diodes don't make much sense.

where is that middle connection going to when it leaves the box (is it connected to the panel in some way) ??

 

[CaptainBob]

Doesn't go anywhere out of the box. No wire is connected to the pictured lower end. Top end seems to be connected to something that goes through the panel to the cells.

 

[Barry Jones]

To answer your question, I think you I would need to know how the three wires going through the box on the soldered wires, are connected to the panel.

 

[CaptainBob]

Thanks for your answers and time.

Unfortunately I'm not going to be able to find that out with damaging the panel irreparably.

What do you think about simply putting a Shottky Diode in series with the + out, just to be safe?

 

[Barry Jones]

I think the middle connection is an earth.

If this is the case, those diodes are pointless.

 

[noelex]

They are bypass diodes not blocking diodes and they are wired correctly. If you are using a solar regulator you do not need any extra diodes. Without a regulator I would add a blocking diode.

 

[exfinnsailor]

Looks like two separate solar panels. The ground is on the left and the V+ for the first one is in the centre so you will get a voltage across these connections. The centre terminal is also the ground of the second panel and the terminal on the right is its output.

So its like two batteries connected together in series to give you a higher voltage. So the diodes are correct ....


..

 

[Barry Jones]

Yes it makes sense if these are bypass diodes for a dual panel system.
They are not blocking diodes as said by noelex.

Are all the three external connections disappearing into your single panel ?

Can the panel be wired without this junction box, as you won't need it for a single panel ??

 

[CaptainBob]

They are bypass diodes not blocking diodes and they are wired correctly. If you are using a solar regulator you do not need any extra diodes. Without a regulator I would add a blocking diode.

I'm using Marlec's HRDi charge regulator which states:

"Note: Solar panels must be fitted with appropriate blocking diodes, parallel panels having one each."

So presume if these are bypass diodes then I'll need to add a blocking diode. If so, would these be suitable (I plan to add more panels later)?

http://search.ebay.co.uk/280554041951

 

[Barry Jones]

Yes the diodes that you have linked to would be man enough as blocking diodes.

 

[CaptainBob]

Thank you all

 

[VicS]

Thank you all

Make sure you get the polarity correct!

 

[CaptainBob]

Make sure you get the polarity correct!

Wilco. Cheers Vic.

 

[noelex]

Yes those diodes look ok. If the handbook for the regulator advises fitting a blocking diode I would do so. (dont disonect the bypass diodes. Blocking and bypass diodes have different functions)

Its unusual most charge regulators disconect the panels when the light levels fall, but obviously not all.