One thing that you always feel annoying is the heat that coming out from the laptops and chargers. We less often care about heat comes from charging adapters than from the machine itself. While the laptop temperature depends on the workload, battery type, and the cooling measures of the design, laptop chargers are also related to these factors.
Laptop chargers consist of an electronic circuit that converts analog current into direct current of suitable power and voltage. It involves rectification, switching and filtering which are done by diodes and semiconductor IC’s. The switching IC’s or transistors are the most heating parts as they handle most power. The whole circuit board is usually enclosed in a plastic casing generally with no ventilation or cooling fans. This is why chargers tend to heat even at low workloads. There are many reasons why a charging SMPS adapter overheats:
Some laptop comes with batteries that draw too much current to charge. If the charging current is greater than the rated current of the charger, there is a risk that you will burn the charger and battery. It’s better to replace your battery if this is the case. In order to verify that the battery is causing the problem, remove the battery from the Notebook and power on the notebook with charger plugged in. If it behaves normally, problem is with the battery.
If you’ve a high-end gaming laptop, it should have a high power graphics adapter. When the game is playing with your charger plugged in (Usually since you wont get enough backup playing high-end games) chargers may heat up which is normal. This always happens with my Dell XPS. The situation gets even
worse if you’re charging the battery along with playing games. Now charger has to supply both power for the battery and for running the laptop peripherals which is the worst case scenario. Try to avoid it by charge the battery to full and run the game or remove the battery and play them if the charger is heating that much. Usually companies taken care of these situation and design chargers according to it.
If your laptop charger is heating up during charging after replacing the battery, the battery must be of a different rating. It happens sometimes that batteries of same serial number is manufactured with different rating. For Eg, the HP MU06 battery is available as HP MU06 Long Life Notebook Battery with extended backup. This might draw excess current than rated current of charger which would cause overheating.