Plugin your garage door opener and check the battery led light to ensure its green.
Liftmaster garage door battery beeping.
Backup batteries open and close your garage door when the power is out and last 2 3 years under normal use.
To test the battery unplug your door opener and activate it using the door control or remote control.
When the battery is fully charged the green light will stop blinking.
So if you only hear beeping when you re shutting your garage door that s normal.
The battery is located on the right side of the door opener power head mounted in the ceiling as you stand under it looking out towards the driveway inside the lens cover behind the light bulb when you pull down the light cover and remove the light bulb you will see the compartment door as it has the 1 4 screw.
If you re using a liftmaster timer to close or other similar technology the garage door opener will beep to indicate when the door is closing.