It's normal for electronic devices to become heated over time and use. The processes within the device result in the components becoming warm. If you notice that your laptop battery charger plug feels hot to the touch, you should know that as long as it's not so hot that it burns you or has a funny smell, it's a completely normal reaction to the electricity being transferred from the charger to the computer. Still, in some cases an overheated charger is the sign of a problem.
You'll notice that your laptop battery charger has a large block that is situated between the plug that goes into the electrical socket and the adapter that plugs into your computer. This block is actually a transformer. It transforms the voltage coming from the wall socket into the ideal amount of voltage required for your computer, usually from the 120 volts coming from the outlet to between eight and 16 volts needed for the computer. This process causes the plug to heat up, which results in a charger that feels warm to the touch.
While it's normal for your charger to feel hot due to its function, sometimes there's too much heat. If your charger or the transformer block becomes so hot that you cannot touch it or you note a strange smell, your charger is malfunctioning and should be replaced. A charger that malfunctions could damage the computer battery, which also may need a replacement.
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What to Do
A charger that is warm but not hot doesn't need any special precautions. If you'd like to keep the charger cooler, prop the transformer box on its side and slide a few pencils underneath to allow better airflow and circulation. Don't leave your computer plugged in all of the time, and when your charger isn't in use, disconnect it from the wall socket to give it time to cool down and to reduce unnecessary energy consumption.
Replacing the Charger
If your charger ever becomes so hot that it can melt other items, is too hot to hold or becomes a fire risk, it's time to replace your charger. With regular use, chargers -- like other electronic devices -- wear away certain components, which results in malfunction. If the charger or transformer becomes too hot and malfunctions, it could result in excess voltage ruining your laptop. Since you don't want a charger malfunction to affect your laptop, it's best to disconnect an excessively heated charger and bring it to a computer repair store for evaluation and possible replacement.