DIAGNOSIS The battery is failing or wasn't fully charged because of a poor dock connection. A healthy 694 should run ~60-90 minutes.
FIX Clean the metal charging contacts on both the robot and the Home Base with a dry pencil eraser or rubbing alcohol on a cotton swab. Corrosion or dust here prevents a full charge.
IF THAT DIDN'T WORK The battery itself is likely degraded. The fix is a replacement battery (model BACS02). Let the robot charge uninterrupted for 16 hours first to recalibrate the battery gauge—if it still dies fast, the battery is the culprit.
HEADS UP Leaving the robot on the dock 24/7 slowly degrades the battery. If you don't use it daily, store it half-charged off the dock.