I have a minute man ups PR01100E it was beeping yesterday and someone pushed the button to "shut it up". When I discovered it had been shut off I went in and reset it. Now it is beeping 3 beeps about every 5 minutes or so. Does this mean it is at the end of its life? Or is there something else I need to do. The farleft green light is on and the far rt light is on. Thanks, sandy