I have an APC UPS for which i replaced the battery few days back.
The UPS shuts down the PC within a minute of going to battery. If manually i abort the shutdown (user alert on PC), my pc continues to run at least 45 minutes! I tried to calibrate the battery, but didnt help (Let the UPS drain down to zero on a resistive load which was 35% UPS capacity. And then recharged to full).
Power chute software usually shows the estimated time, but shows nothing here now.