UPS Failure

During a brief power outage today, I discovered the hard way that one UPS was no longer working. Only after a self test did it reveal that the battery needs to be replaced. This strikes me a being a poor design for a UPS. Well, it is a cheap UPS so I suppose, "You get what you paid for it." I guess I should have been testing each UPS regularly and not assumed they would indicate a problem automatically. Assuming is bad.