The Battery Disk Tray Open alarm is caused when a circuit breaker associated with a battery tray is tripped or in the “OFF” position. 

When this alarm is activated the system may not be able to run off of the batteries, as they may be disconnected.  Verify that all of the battery tray breakers are in the “On” position, even if the battery tray does not contain any batteries.  The battery tray circuit breakers are tied in series to the alarm detection circuit, so they must all be “On” in order to clear the alarm.