DIAGNOSIS The periodic beep indicates the backup battery is depleted, failing, or not properly connected. The system is alerting you it cannot function during a power outage.
FIX Replace the backup battery. The required battery is a 12V, 18Ah sealed lead-acid battery with F2 terminal connectors. Disconnect the old battery's red and black wires, remove it, install the new one, and reconnect the wires. The beeping should stop immediately upon establishing a proper charge connection.
IF THAT DIDN'T WORK If beeping continues with a new battery, the charging circuit in the opener may be faulty. Check the fuse on the opener's main control board. A blown fuse will prevent battery charging. Refer to for the fuse location and replacement spec.
HEADS UP The battery is essential for operation during a power outage. Do not simply disconnect the battery to silence the beep. A non-functional backup system will leave the door locked shut if the power fails.