Lithium-ion (Li-ion) batteries tend to become dangerous when they are overcharged at high temperatures. Safely charging these batteries has become one of the most important design specifications in battery-powered portable equipment. Progress has been made in establishing industry standards such as the Japan Electronics and Information Technology Industries Association (JEITA) guidelines for improving battery-charging safety. This article addresses safety requirements and battery-charger solutions that meet these requirements in both notebook and single-cell handheld applications.