BACK-UPS BN4001 120 Vac (aka Back-UPS Network 40)

[coljediv]

My unit (BACK-UPS BN4001 120 Vac) sounds its alarm periodically for 5 seconds or so and illuminates the red light.  None of the attached devices are affected when this happens.  I have a minimal load:  a Netgear switch (that also provides PoE to a Netgear access point) and an ADT gateway.  I think this started happening about a year ago, and I thought maybe the battery was nearing end of life, so I replaced the battery about one month ago.  But the symptom continues.  After about 5 seconds or so, the alarm silences itself and green LED resumes without me doing anything.  As a note, if I pull the power plug, battery power is provided as it should to the attached devices.  Any thoughts why this would happen?

Could it be a problem with the circuit it's on, like too much demand or some other anomaly?  I know that circuit is more used than any others in the house and it's only 15A.