I had a Dell latitude, purchased as a refurbished unit, that had this identical problem. The source of the problem was a 'sound device", possibly a buzzer, in the left front of the unit, just alongside the battery compartment. I appeared the device was jammed on, got hot enough to melt the plastic a tiny bit, and "welded" the battery to part of the plastic shell there. I had to dissassemble just about everything to see this, and then a swiss army knife broke the "weld" and all was OK.
I tried calling, Dell, but this unit was reburbished and otherwise OK, so by the time I got down to tracking down the problem, Dell didn't want to hear from me.