Why does the DIY “solar panel circuit” show battery voltage and not solar panel voltage?

batteriessolar cell

I have six solar panels but each are different from one another. The first is 4.5V. The second is 6V. And the last four are all equal up to 6V. It all adds up to 16.5V in series or on a good sunny day, 18V max. That's what my multimeter says.

I have a 1N1914 diode connecting to the positive lead connecting to my double pull switch. Now for my batteries, I have one 9V rechargeable battery and 4 AA (1.2V each) rechargeable batteries. The batteries total to 13.8V.

When I try to charge my batteries, it doesn't charge any of it. The switch actually works fine. But when I try to charge the batteries, the meter shows my battery voltage rather than my solar panel. What am I doing wrong?

Best Answer

Without more information, it is hard to know your problem. Using a different diode as suggested would help.

Also, your panel voltage might be = your battery voltage. What I mean is that the 1.2 volt Ni rechargeable batteries are rated 1.2 v nominal and quickly rise to 1.4 volts or higher depending on the brand when charging - this brings you up to 15.6 volts just for voltage rise for the AA with no voltage rise for the 9V, also you have the voltage drop of the panel from the diode - this brings them basically even!. I don't know what type of chemistry your 9 volt is, but if it rises when charging as well, then battery voltages will have risen to the panel voltage very quickly and then stopped charging. Try taking out a few batteries and see if it starts charging!

Good luck.