| With the development of society, the portable electric devices are used more and more widely in our daily. Being the power supplies of electric devices, the batteries are booming because of the huge market of portable electric devices. Considering the reusability and environmental protection, and the Lithium battery becomes the best choice of portable electric device because of its unique advantages, such as high energy density long circle life, high voltage and absence of memory effects.In order to satisfy the demand of higher voltage and more capacity for portable devices, Lithium battery pack can be used as the power supply. However, the comparative fragility of Lithium battery, such as, over-charging and high temperature, imposes stringent requirements on charge and discharge circuit. It is essential to take measure to monitor the parameters of Lithium battery pack such as voltage, current, temperature and design reasonable protective circuit for them.At present, although there are several relative matured management concept of lithium battery for high-grade portable electronic devices ,for example notebook PC and mobiles. Deficiencies such as mainly severing for lower power supplies of devices (single battery or the battery pack under section 4), low inflexibility, inapplicable to latest devices exist the current concept because of the specialized method. The thesis mainly aims at relative smaller current portable electric devices. The intelligent monitoring system designed with ATmega128 as the core controller provides protective function for the Lithium battery pack. The acquisitions of Lithium battery real-time voltage, current, the temperature through ATmega128 controller can be served for dynamic protection controlling and the remaining power estimation and also they can be displayed on lcd.Charging and discharging of controlling is proposed in the thesis.In the pre-charge stage, Lithium battery pack is charged with small current under the control of PWM waves .The system can timely cut the circuit and provide alarm signal when emergency existence. In the thesis, the studies of performance parameters, charge and discharge characteristic for Lithium battery provide theoretical evidence for controlling .The voltage and current detection solutions and the hardware circuits are presented .The differences showed between the batteries to certain extent, can cause phenomenon such as over-charge and over-discharge and even reduce battery lives. Balance controlling with resistance raised protect the Lithium battery neither over charge nor over discharge. And the useful time of the Lithium battery pack can be extended with this method. The state of charge estimation to the Lithium battery pack presented in the paper has a good reference value.Compared with the integrated chip protection method, the method designed with micro controller and peripheral circuit has more generally application. It can timely protect Lithium battery pack and prolong their service life.
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