I've got two solar panels which each provide 9V. I need them to provide 18V, and according to different sources (such as this forum thread) that should simply be a matter of connecting them in series.
So I did. I connected the negative on panel A with positive on panel B, and positive on panel A with negative on panel B. As far as I understand, this is how you connect solar panels in series.
However, I came across a surprising observation. Each of the panels produce about 10V - 11V each on a good sunny day. I've checked (and double checked) readings on my multimeter. However, when I connect them in series the voltage drops to 4V - 5V. I get this reading on both solar panels by connecting my multimeter to the connectors on any two of the solar panels. As you've probably figured out, I don't understand why this happens.
Now, the panels have 4 soldering connectors each (see below picture). The first two are positive and negative (which according to my multimeter outputs nothing) and the two second ones have some chinese letters next to them which I've got no idea what means. However, these connectors (the ones with chinese symbols next to them) are the ones giving 10V - 11V. These are also the ones I've used to create a connection from panel A to panel B.
Since I could not figure this thing out, I called a friend. I was advised to put Schottky diodes in between them in case the panels somehow was discharging through each other. So I did. However, still only 4V - 5V when i put them in series.
Right now, I'm at loss what to do. How do I connect these panels in series to get 18V from them?
- Each panel outputs 10V - 11V
- Connecting my multimeter to the bottom and top right hand (or left hand) connectors indicates resistance, so these can't be the same connectors as that should give zero resistance as far as I've been told.
- The connected solar panels give 4V - 5V regardless of whether I've got the Schottky diodes in the middle or not.
What am I doing wrong?