DIAGNOSIS The sealed lead-acid backup battery has reached end of life. The alarm is a low-battery warning. These batteries typically last 3-5 years.
FIX You need a replacement Genie Battery (part # 30820T). Disconnect the opener from AC power by unplugging it. Remove the light lens cover on the front of the motor unit. Locate the black battery box. Disconnect the red and black terminals. Remove the old battery. Install the new one, connecting red to red, black to black. Reconnect AC power. The system will run a self-test.
IF THAT DIDN'T WORK If the alarm continues with a fresh, verified battery, the logic board's charging circuit has failed. The entire power/control board assembly would need replacement.
HEADS UP Use only the specified Genie battery. Substitutions can have wrong terminal types or voltage and may damage the charging circuit. Dispose of the old battery properly at a recycling center.