Insert the battery as indicated in the instructions (‘+’ sign to the outside)
Do not fill the reservoir.
Switch the unit on by placing the 2 red discs opposite each other (for at least 2 seconds):
If you hear a beep: the battery is working, you can fill your reservoir and use the collar.
If you do not hear a beep: the battery is worn out, replace it with a new Martin Sellier battery of the same type.
Note: Testing the battery with a voltmeter will not give a reliable result as voltmeters test voltage and not amperage.