Introduction There are more and more portable devices in the market today. Examples of portable devices are cellphones, MP3 players, cordless phones, and digital cameras. These devices become more common as they get less expensive. In order to support the increasing number of portable devices, more battery chargers are designed. The reliability of a battery charger is important in ensuring that it does not overcharge. This prolongs the lifespan of a battery and reduces damages to its internal components.