Answer to: UPS is constantly quick beeping and shutting downHere's a suggestion that I received from APC tech support: Do a "brain-dead reset" (their terminology, not mine). Unplug the unit (and all devices connected to it). Disconnect the battery (one terminal will do). Press and hold the power button for 20-30 seconds. That's all there is to it! Can't guarantee that it'll work for your problem, but it worked for me, and I had a similar-sounding problem.