I'm outside in full sunlight trying out some new solar cells I soldered together. I have a string of cells lined up like this:
My DMM reads 3.14V open circuit and 0.8A short circuit. I take two more strings and connect them like this:
My DMM should read something like 3.14V and 2.4A. Instead, it reads 3.14V and 1.61A.
I thought I may need diodes for each string, so I did this:
I expected a voltage drop and sure enough my DMM read 3V and 0.52A. Next, I made this:
I was expecting 3V and ~1.5A. Instead, I got 3V and 0.82A.
I've never experienced parallel solar cells having a current drop like that in my other solar panels. Not only is the current lower after I add a diode, it's even lower when I connect them in parallel. Outside of possible bad workmanship on my part, is anyone aware of a possible cause?
Here are pictures of the (HOW-IN-THE-WORLD-IS-HAPPENING) phenomenon. Each string of solar cells are color coded. The cells having this current reduction issue are the bigger ones. Each picture shows short circuit current with my DMM (sorry Kevin White haha). I used a lamp, so yes the current is gonna be tiny, but it suffices.
1st string of malfunctioning cells: 0.51mA
2nd string of malfunctioning cells: 0.36mA
1st and 2nd strings of malfunctioning cells in parallel: Should be 0.51 + 0.36 = ~0.87mA. Instead, it's 0.43mA
And for the sake of a control group, 1st string of normally functioning cells: 0.3mA
2nd string of normally functioning cells: 0.28mA
1st and 2nd string of functioning cells in parallel: Should be around 0.3 + 0.28 = ~0.58mA. It's 0.6mA :)
And finally, to validate my point, 1st and 2nd string of normally functioning cells and 1st string of malfunctioning cells in parallel: Should be 0.6mA + 0.51mA = ~1.1mA. Instead, it's 0.53mA.
It's almost as if the bigger cells are siphoning off current. I tested for shorts. Looked for corrosion and bad construction. Nothing stands out.
WHAT IS GOING ON?!