I agree with Bert, I always remove the battery. They will cause grief eventually! Use either in UPS or the separate DC input jack on the rear. One note, if the battery is removed and the battery charge switch is in the position to light the front panel lamp you will degrade the stability of the unit! Removing the bulb clears it up! Never bothered to figure out why! Also I usually remove a battery A2 and install two shottky diodes on the underside of A2s chassis jack. Non-battery units have an A2 that just has these two diodes on it. Cheers, Corby