Battery-powered electronics devices have become well-verse in the current society. The rapid growth of the use of portable devices such as portable computers, personal data assistants, cellular phones and Hybrid Electrical Vehicles (HEVs) creates a strong claim for fast deployment of the battery technologies at an extraordinary rate. The design of a battery-power-driven device requires many battery-management features, including charge control, battery-capacity monitoring, remaining run-Time information and charge-cycle counting. Compare to other batteries, lithium battery has the highest power density, energy density and the longest cycle life. The main objective is to develop a battery management system model to ensure that optimum use is made of the energy inside the battery powering the portable device and that the risk of damage to the battery is prevented. Modeling a battery management system by studying the charging and discharging characteristic curve of the lithium-ion battery is being proposed in this research project. © 2012 IEEE.