Back-UPS 600 goes straight to battery?

[Mastiff37]

I had an incident where my back-UPS 600 went into battery mode and the battery was fully drained.  This was a little odd since the power only blinked out.  I disconnected it and found that it would not turn on, even when plugged in.  The symptom was that it would come on and blink green for a few seconds while beeping, then turn off.  Maybe this is the expected behavior when the battery is dead.

I left the unit plugged in all day and found that it would now blink green for a few seconds, then go solid green.  But when I plugged my computer back in, it only worked for a minute or so before it started beeping (constant tone) and the power button turned yellow.  I believe this means I'm on battery power.  The software indicates 99% battery charge and the outlet is verified to be active/alive.

What might be going on?

EDIT:  The unit is back to where when I plug it in and turn on with no load is starts (continuous) beeping while the light is blinking green.  Then the light turns off and beeping continues.  The battery may be slightly down from running the PC for a minute, but that's it.  Trying to know if this unit is broken or can somehow be salvaged.

[JonPro]

Hi @Mastiff37,

Thank you for using the SE Community Exchange! My name is Jon, your support specialist who will work with you on this query.

May I please know how old is the UPS and its model number?  This would help us know what procedures we can do to assist you.