Charging technology is becoming more and more important since rechargeable batteries are commonly used in many applications than ever before. To facilitate various charging profiles, a battery charger with multi-mode is proposed. The charger is composed of an innovative reflex charging circuit and a controllable half-bridge converter with pulse-width-modulation. This multi-mode charger provides not only four basic functions of constant voltage (CV), constant current (CC), pulsed current (PS) and reflex charging (RX), but also the multi-stage charging with hybrid charging modes. The desired charging profile can easily be accomplished by adjusting the controllable parameters of the charger. In order to simplify the control circuit, a digital signal processor (DSP) with the associated sensors and interface circuits are used as the control kernel. By continuously monitoring the charging current and battery voltage, the charging modes can be adapted to the charging strategy. An experimental charging circuit is built and tested. The experiments in this dissertation are carried out on lead-acid batteries, Experimental results show that the charger is able to execute the charging functions of various tentative charging strategies with hybrid charging modes.

Due to the differences in batteries of a series-connected battery bank, the restored capacity in each battery may not be the same when being charged. In order to extend battery cycle life, the charger for the battery bank must have the capability of charging equalization. This thesis proposes a non-dissipative balance charging circuit based on buck-boost topology for a series-connected battery bank. Each battery in a battery bank is associated with a buck-boost converter. This topology can efficiently alleviate the unbalance of charge among batteries by taking off the charge from the affluently charged batteries and then allotting to those insufficient ones. To accomplish this complicated and accurate control, a digital signal processor (DSP) with sensors and interface circuits is adopted. It monitors the variations of battery voltages, activates the associated buck-boost converter, and adjusts the duty ratio of the converter to regulate the energy to be released. In virtue of the adoption of digital control kernel, the control circuit can be simple and the control flexibility can be favored. A battery bank with four series connected lead-acid batteries is used for illustrating the operating behavior and describing the operation modes of the balance charging circuit. The results of experiments convincingly advocate the applicability of the proposed approach.

This project deals with design and study wireless security device. This device works in ISM band, created by two modules handling secure subject. Microprocessor AVR from company Atmel provides communication between these modules.