My UPS was beeping constantly (faster then the out of AC power beep).  Disconnecting the battery - still beeped!  Checked on the APC website and the device is discontinued. I took it apart thinking that maybe one of the internal fuses went.  Nope.  I then searched forums for tips and came up empty.  Finally I just unplgged the thing and let it sit on the bench for a week or so. I then cam back an hooked a known good battery to the unit and plugged it.  BAM!  that fixed it.  seems the battery really was dead but it would not recognize a NEW good battery until the unit sat and discharged completely ???  weird. Anyone else have similar or other experience like this ?     

Here is an update.  It all SEEMED well for a couple days. Then suddenly the unit started doing the 3 battery low beep. then within a minute four beeps followed by a continuous beep.  I am guessing the charging curcuit is marginal and it eventually failed.  Still have to get the DVM out and check the battery voltage.  But I am betting its near zero volts.