I have two solar panels connected in series, and I'm using them to charge a phone. Together they provide about 7 V when I connect their leads to a multimeter or a basic circuit (i.e. Resistors/etc.). To regulate the voltage/current, I connected them to a step-down buck-boost converter.
The problem is that the output voltage of the solar panels drops significantly as soon as I connect them to the converter, from 7 V to about 1.5 V. This does not happen when I use a regular source (i.e. A laboratory voltage source - a machine).
I tried adding a diode/Zener diode to the solar panel to make sure the current is going in only one way, but that didn't work. Additionally, I tried to isolate the solar panels from the converter by connecting it to a voltage follower circuit or any IC, but that didn't work either.
I'm not sure why this voltage drop is occurring or how to prevent it from happening. Any help would be greatly appreciated.