Often, a laptop battery charger will malfunction or fail to work at all. Various signs of trouble may indicate different problems, some of which can be addressed. In other cases, though, the charger should be replaced.
Noise and Buzzing
A light, high-pitched buzz or tone emanating from a laptop battery charger is not uncommon. Typically, you can hear this only if you place your ear close to the charger. However, if the noise becomes loud enough to bother you, you may want to replace the charger. A loudly buzzing charger doesn't necessarily mean there's something wrong with it, especially if it is functioning properly and not overheating. But it can be an unnecessary annoyance.
Cords and Connections
One of the most common problems with a laptop battery charger is improperly connected cords. Most chargers have one cord that must be plugged into an electrical socket and another to be plugged into the laptop. If either plug is not connected properly, your laptop won't charge.
Old and Damaged Chargers
Some older chargers eventually lose their function and need to be replaced. They typically cannot be repaired. Usually a battery charger will outlast the life of a laptop. But chargers that have been dropped repeatedly, had liquid spilt on them or have been left in the sun and heat won't last as long as they should.
A charger that has a unit or cord with a short in it, also known as short-circuiting, can be dangerous, and should be replaced. You can typically tell if a charger has a short by the way it charges. If you have to bend the cord to a certain angle or position for it to keep charging, it is likely that it has a short. Shorts can be caused by the charger's tip accidentally coming into contact with metal, the cord or tip being roughly handled or pulled out of the laptop or the cord constantly being tightly wound up.