Why wont battery charge on laptop

A) The Battery is old, and beyond charging

B) The AC adapter (Charger) may be bad, and/or one of it's cables may be bad. If there is no one to test it with a multimeter, take it to a computer repair shop, and have it tested.

If bad suggest you look around at prices on the internet, before buying one from the repair shop. (If offered)

C) The port on the laptop, that the AC adapter (Charger) plugs into, is the DC Power Jack. (May be labeled as DC IN )

This jack may be soldered directly to the motherboard, in the laptop, or is attached to a cable which plugs into the motherboard.

For the style that is soldered directly to the motherboard, it's solder connections may have received damage.
Normal plugging in, and unplugging, may have cracked it's solder joints.

Bad connection caused by cracked solder joints, could = no power to battery. (Even though the laptop May be receiving power)

If laptop operates fine on the AC adapter, but the Battery will not charge, the problem may be a power sensor chipset, on the motherboard. May require replacement of the motherboard.

{ This chipset senses;
A) When the battery needs a Full charge, or just a trickle charge.
B) When the battery needs No charge, and power just goes to the laptop.
C) When the Battery needs a trickle charge, or full charge, and the laptop also needs power }

Regards,
joecoolvette