mc4 junction box???

Re: mc4 junction box???

Welcome to the forum... Your first post did come through--You should not need to create a second thread. It will spread the same discussion across several threads.

I will past some links for you to read/watch... Hopefully they will help you understand. Otherwise, you may need to post pictures of the parts and real of the panel if you need more information:

http://www.electricaltechnology.org/2013/03/how-to-get-connection-from-solar-panel.html

This is a video--Note that the narration is wrong--that is a BYPASS DIODE, not a blocking diode (above link shows bypass diodes and how they are installed).

http://www.instructables.com/id/How-To-Build-A-Solar-Panel/step8/Installing-the-Junction-Box/

If you have glass panels with teldar or some sort of thin plastic backing, then you will probably use type 2 neutral cure silicon seal. If you are using wood backing--you probably will add a couple screws to hold the J-box down (and some silicon sealant).

Does this help... If not, can you be a little more specific with your question(s)?

-Bill

Re: mc4 junction box???

If I did not make any mistakes--The "middle diode" bypass diode should be replaced with a jumper wire (or you can put a jumper wire across the two middle terminals if they will hold the extra wire with the panel connections too). You only have two strings and a box designed for three strings.

I would not even use the blocking diode unless you have no solar charge controller and are directly connecting the panels to a 24 volt or higher battery bank. And if true, I would use a single external diode per string (less power drop as you only have one blocking diode and better cooling for the diode).

Lastly--Just to be safe--Home made solar panels, especially when you are getting larger panels and strings of panels can be a real fire hazard. If you install these panels unattended, they should be somewhere that if there is a fire, it does not put property or people at risk.

And for any panels, there should be an inline fuse/breaker (such as a protected combiner box) per string if you have (typically) three or more strings connected in parallel.

Panel Fire Question

There are other details about DIY solar panel construction that make them very difficult to justify for building them at home (for example, many times EBay'ed cells are mfg. rejects because, for example, they have current defects which can cause cell failures/overheating).

With commercial products below $2 (and even sometimes near/below $1 per Watt), we try to discurage people from making there own panels as other than a learning experience. Most DIY panels will only last weeks to a couple months if permanently mounted outside in weather.

-Bill