# Multiple DC Input to Single DC Output

I want to connect solar panels in parallel, not sure whether connecting the terminals together will work. If one solar panel produces high voltage, it will block the voltage generated by second solar panel and it never contributes to the total power generation. This is my theoretical assumption. If I have a Multiple DC input which can take range of DC voltages, it can convert variety of voltages to a single constant DC voltage output. Not finding how to achieve. Please help.

• Switch mode DC to DC converters is a clue Commented May 31, 2013 at 17:19
• Buck converter is even more of a clue Commented May 31, 2013 at 17:24

Connecting them in parallel may be a problem since the lower voltage cell will drain some current from the higher one. I don't know if this will damage the cell, but it doesn't seem healthy anyway.

Basically I can think about two options: a DC converter for each cell to equalize their outputs, or an electronic switch (like this one) to select just the higher source (and maybe redirect the lower one to a battery). Even then you'll need to somehow regulate the output (since both batteries and loads will probably have an operating voltage range to be met). But those things would be a bit of reinventing the wheel, since you can purchase a ready-made charge controller to take care of these things.

• There is an diode in Solar Panels rated (1000V) to make sure it does not drain the current from the higher voltages. So that is protected. Charge Controllers takes just only one input and generates output. Problem is, Output of Charge Controller is not exactly the same of adjacent charge controller. Now instead of solar panel, you need to work on Multiple Charge Controllers Voltage fix before it goes to battery. Commented May 31, 2013 at 17:49
• Well, if the only thing you need is just to have the higher voltage panel providing the output, I guess the diode will do. But you're not using the power generated by the lower voltage panel then, right? Commented May 31, 2013 at 22:11
• About connecting multiple charge controllers together, I guess you'll have to look for ones that have/support a SYNC cable between them. Also take a look at electronics.stackexchange.com/questions/17092/… Commented May 31, 2013 at 22:20
• Yes, you are correct. That is why I want to take the inputs from individual solar panel to a multiple dc input to single dc output. this way, circuit need to increase or decrease the output voltage, which charge controller does. Problem is, No charge controller has more than one input. Commented Jun 1, 2013 at 16:30
• If your panels are relatively small (i.e. tens of Watts) you could use an inexpensive buck converter for each one, as @JIm Dearden suggested in the comments, for instance the LM2678. For higher power, probably the best would be to have one charge controller per panel, and connect them via SYNC cable. Commented Jun 1, 2013 at 21:57

It seems that quite a lot of people just reccomend connecting panels with the same nominal voltage in parallell directly, e.g. http://www.solarenergyproducts.com.au/wiring_solar_panels_in_parallel.php

As long as the panels have the same nominal voltage and are in the same orientation and not shaded, this should work fine.

• In an ideal case it should work. If there is a voltage difference between panels it reduces efficiency. Based on my understanding on voltages, The one with lower voltage electrons will never get a chance to enter into the charge controller, unless the voltage drops down. The one with the lower voltage will never contribute the power to the system. Is my understanding wrong? Commented May 31, 2013 at 17:55

A solar panel is nothing else but a DC power supply. If you have to connect 2 DC power supplies in parallel so that one does not interfere with another - what do you do - you use a blocking diode/s between them. I hope this helps you. Also see this site: http://www.mpptsolar.com/en/solar-panels-in-parallel.html