Including the solar panels.
How to test voltage on a solar panel with multimeter.
You want to choose a voltage range capable of displaying the maximum possible voltage of the panel in open circuit this means that if you have a panel rated for 20 volts you should set the multi meter.
The next step is to ensure that you select a voltage range that can display the possible maximum voltage of your solar panel in an open circuit.
A multimeter is a device that you can use to test the voltage and current of any device.
Some exceptions may apply based on panel type.
Open circuit voltage can vary depending on your solar panel but the readings we are usually looking for are in the range of 15 to 23v.
To test a 18v solar panel voltage output directly put your solar panel in direct sunlight set your multi meter to the dc volts setting.
Simply touch the solar panel leads with the multi meter probes matching their corresponding polarity red to red black to black.