The DC cable connecting the laptop with the AC power adapter has several spots that can cause trouble:
- The DC power plug - with 2 or 3 pins.
- The ferrite blob - filters out electromagnetic pollution
- The joint at the AC power adapter casing
When the laptop still runs on the AC power adapter but does not charge the battery, the “3rd wire” in the DC power cable might have been snapped or the soldering at either end of the cable broken.
In rare cases wires can also snap at either side of the ferrite blob. Most likely reason is excessive twisting, force or bad soldering.
Back to the laptop battery charging diagram.