Turn on the microphone
If you turn on the mic and the light is "Green" then the battery is good!
If you don't get a green light if it is RED or no light at all the battery needs to be replaced.
This is a picture of a "Used" battery
Here is the hours of operation per battery level
To change the battery Open the battery holder at the bottom of the Mic case
Remove the battery
Replace the battery with a new one and make sure you line up the battery terminals properly Large and Small terminals go into the mic battery slot matching the sizes.
Turn on the mic and make sure you are full battery.