Tripp-lite SMART1500LCD strange behavior o loss of utility power

Hi folks,

I have been playing around with a new Tripp-Lite SMART1500LCD being monitored with PowerAlert office.

I have a test load attached wich shows 37% output utilization and 14 minutes runtime while on utility power with a full battery. When I switch off the utility power the indicated output utilization jumps to 90% and runtime drops to 4 minutes. When I restore utility power after about a minute the utilization returns to 37% and the runtime increases to about 9 minutes. 

Is this the expected behavior?