My IBM Think Pad T30 showin working on AC with out... (by 2 users)

there is a switch in the plug end to the back of your comp its like a little swinging door that when you unplug out of back of comp this switch engages battery now if you unplug just from wall its going to see these 2 things the doors not shut but i have to keep working so it sets aside the plug still recognizing it of course but running off the battery trying to still find out why the powers not there but the plug is still plugged in and it will continually search until it reaches its falt point of dead battery
its like a battery backup for your system it gets unplug but wants to know where the power is

now in reference to the little swinging door i call it its a power over relay in your comp for some reason its not closing properly to allow battery to run by self
this is usually just a switch that needs adjusted in the motherboard configuration