In the how to test solar panels video that you posted there is no controller connected to the panel.
Voltage tester is not reading solar panel.
Some exceptions may apply based on panel type.
Keeping in mind the coefficient common readings are.
Grid tie solar panels with 60 cells are often referred to as 20v nominal panels like the solarworld sunmodule 290w solar panel.
The reading should be within 10 of the specs on the rear of the panel.
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.
They have too high of a voltage to charge a 12v battery bank with a traditional charge controller but too low of a voltage to charge a 24v.
Open circuit voltage voc to test open circuit voltage take your multimeter and set it to voltmeter and place the probes in the correct connectors and set to volts dc.
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.
After doing your solar panel testing you should find that the solar panel output for the pv panel you built on the make solar panels page is about 18 volts and 3 5 amps.
Testing the 12 volt solar panel.
Before disconnecting the alligator clips ensure the multimeter has been turned off.
100w 12v 36 cell panel 20 22 voc.
Simply touch the solar panel leads with the multi meter probes matching their corresponding polarity red to red black to black.
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.
Test your solar panel regulator sometimes you will want to check that your solar system is performing properly or you may simply want to know what output your panel is giving.
Whenever you have these two values you can figure out the wattage by multiplying them together.
This is not unusual.
How to test a 12 volt solar panel vs other voltages.
It starts to get tricky when you move away from battery based solar systems and the 12v increments are no longer necessary.
They tested directly from the panel output itself.
All you need is a multimeter.
If you re the solar panel you are testing is used you may receive a lower reading.
Testing your solar panel is easy.