Introduction: How to Change 36V to 12V Solar Cell
Disclaimer: Do this in your own responsibility, the panel warranty will void also the delivered power may go below a certain voltages which can cause a severe damage to your electronics. do this in your own responsibility.
In this bad situation (WAR) having a shortage of gasoline, diesel, and electricity in Yemen my country. I tried to find an alternative source of power. I went from my village to the nearest town to find anything, I was lucky. I found a shop open selling a solar PV's but the problem was they were all 36volt. We do not have any 36-volt inverters only 12-volt are in the market and I cannot get to the nearest city due to the lack of security and gasoline.
Step 1: What to Do.??
What to do.??
I found that the solar panel was made of 72 cells and they were divided into 3 groups each one made of exact the third of the total (24 Cells). Therefore, this was the light for me. It means that I can divide them into 3 groups each of 12v that I can make a use of.
I bought one solar panel with a small same power rating inverter (300Watts.)
Step 2: The Inverter
Now I can use the 12-volt inverter, which I found in the market.
Step 3: J-Box
I opened the J-box that was in the back.
I were really happy to find that it has 4 pins. Showing me that I have three sets of 12volt panels connected together in series to give 36volts.
I will reconfigure them from series to parallel and walla
Sadly, I found they were interconnected not from the J-box they where connected from inside the panel itself (the only use of making a 4 pins out into the J-box is to connect the shunt diodes which if you have more than one solar panel connected in series and one of them burnt-out or damaged the diode will pass the other panels current to by-pass the faulty ones).
Be careful when de-solder and when dismantle the J-Box. the leads or pins are very soft and may torn or cut by the paper knife..
Step 4: Connections
Here is how I disconnected them from inside. But take this in your mind, if you are reconnecting them from series to parallel, you no longer need the shunt diodes because there is no current to be bypassed if you have faulty ones but in the other hand you need a blocking diodes instead of them to block current from flowing from one panel into another. If you do not connect blocking diodes after each one of the panels that you have, you will probably have a discharging current flowing into the weak or faulty panels and loss your power.
Step 5: Tracing
Trace your internal panel wiring. You will find that they are connected in series by three conductive strips. I used a paper knife to take out the back sheet and also to disconnect them. After peeling the back sheet to open about 2cm gap, cut the conductive strip twice with an approximately of 1cm space and take out the strip. So now we are having a gap of 1cm in the strip and also a 1cm of the strip is showing to us. This is the place where we will Iron our cables in.
Step 6: Shunt Diodes
Using a voltage meter to find out the positive terminals and the negative ones. I solder the shunt diodes in the positive leads to make them work as blocking diodes.
(Sorry, the pictures lost. the shown is the diodes covered by electrical tape)
Step 7: Wiring
Now, solder your wiring reds for positives and blacks for negatives. Then join all the reds together (I have soldered them) and the blacks together.
I made a hot glue to the iron surfaces, but it melts due to sun heat.. change them with another proper covering that you can find.
Due to the living situation I'm stuck in. I do not have any DC wires neither the near town. I need at least a 4mm or more wires. I have only 1.5mm AC wires. I tried to connect them from the panel to the inverter about seven meters along. I could not draw more than seven amps of the grid. and as I calculated, it should be at least more than 20amps (8x3=24amps max). So, I connected three wires in parallel instead of one and reallocate the inverter to nearer place. Now I can draw 22 amps.
Step 8: In-Line Fuses
Also, I connected a 7.5 DC fuses in line with each one of the solar groups to protect them from burning due to over-current. In addition, I bought a 1.5 amps AC fuse and mounted it into the 13Amps plug to protect my inverter from over-current and electrical shorts in the house. I Secure the 1.5amp fuse in by small pieces of the melted glow.
Step 9: Finish
Now happily I have electrical power from 7am to 5pm that runs fans and charges laptops, mobiles and lighting for the night.
Later on I have changed the place of the inverter to protect it from direct sun light and rain. its now indoors and also make the wires a little bit longer then do a half circle to down then up to make the rain drops not to reach the inverter.
Michael Heng made it!