If your using Haymakers pixcontroller board then make sure dip switch "6" is on. If this switch is off, then you are in fast shutter mode and the camera wakes itself every 2.5 minutes instead of every 3.5 hours.
Make sure your D-380 is setup for the best settings also. Open the door of your camera to turn it on, press the "ok" button on the back of the camera, use the right arrow to go into "mode menu", arrow down or up to "set", this changes to "setup" when you get to it, press the right arrow, change the "all reset, the "beep" and the "rec view" all to off(these will be the first 3 items listed), now press "ok" to hold these changes. This will save some of that lost battery power.