Slayer69

Hi DrLOLCat,
 
My system uses a built in MPPT, so I can't comment too much on the MPPT side.
 
However I have learn't alot from building my own solar panels and comparing them with factory produced panels.
With my panels I did in a single string of solar cells. Downside to this in that covering just one cell means a drop in the entire panels output.
 
However the manufacturers are quiet clever in this regard. I opened the junction box on the back on my Jinko 235w panels to see how they connect them all together.
My findings are that they split the panels into 3/6 different sections. So basically it's 6 strings combined into one with diode bypasses connecting them all together.
This means that shading of on cell effects only that string, so only a 6th of the output is effected. The panel will just bypass the string that is suffering from shading.
 
How the MPPT's use this to produce max power is a bit above my pay grade
I'll attach a pic of the back of a junction box so it makes better sense.

Ok, so I thought it might be a good idea to do a step by step of how I mount my solar panels on the roof.
 
Firstly, I am NOT saying this will work for everybody, or that it is the correct way.
This is just how I have done mine to save costs, as the original equipment from the solar companies is extremely expencive.
 
So, I use electrical stuff every day at work, so it was logical for me to use what I have learnt there.
 
All the following is part numbers from Cabstrut and your local electrical supplier should have it available.
I got mine from BES (Bellville Electrical Services) and Mr Koen there gave me 40% off from the listed Cabstrut price.
 
The following should be enough for me to mount 8 x 235W panels.
 
4 x P2000 (1mm thick)
20 x SN110/M10 (M10 nut mounted on a spring. This fits inside the P2000 rail)
20 x P1063 (Square piece with 11mm hole in the centre. Using this to fix adjasent panels)
20 x M10 bolts
10 x P1026 (90 degree angle. Will use it to fix the panels on the ends)
All the above worked out to less than R1k
 
1st step was to make sure I knew where I wanted to mount the panels.
2nd was to start opening the concrete roof tiles to find out where the roof trusses is located.
Here I used Tri-Strap that I got from Brights. I used 35mm long self drillers to fix the Tri-Strap to the roof truss.

 
Next step is to bend the strapping and cut it to the correct lenth.


 
Next would be to close the tile gap again and do the rest. I used 3 fixing points per 5m length of P2000.

 
Once all the straps is done, it is time to fix the P2000 to the straps. Here again I used the 35mm long self drillers.

 
Final product

 
Next week I hope to start mounting some panels.

Power.
Normally the power rating of a panel will be given as Pmax or Wp.
This means the maximum of power the panel will deliver when tested in the factory. This is normally done at 1000W/m2 at 25C cell temp.
Also note that most manufacturers allow a +-5% variance on power delivery.
Some manufactures can also supply Nominal power figures.
This is normally done at 800W/m2 and at 45C cell temp. Should give you a much better idea of what to expect in real world conditions.
 
Voltage and Amps at max power. This is basically the voltage and amps your MPPT solar controller will try and control your system to, if possible.
 
Open circuit voltage.
This is extremely important to know this value, especially if you going to connect more than one panel in series to a solar controller.
If your solar controller input is rated 50V max, and you connect 2 x 24V PV panels, it might sound ok on paper, but the open circuit voltage might be 29V, and that could either blow the solar controller, or cause it to stop working.
 
Short Circuit Current.
This is the maximum current that will flow through the wires of a PV panel if they are shorted out.
I would use this as a good benchmark for sizing cabling to and from the PV panel.
 
Maximum System Voltage.
This is a good indication of how many panels could be connected in series.
 
Say max system voltage is 1000V.
Open circuit volts is 29V.
Max panels in series is then 1000/29 = 34.48 Panels, so 34 panels in reality.
 
Here is some examples....
.
 
DS_Sovello_Project_Pro_P_V1 5.pdf
 
TE190-220-54M.pdf