| Electric-Vehicles are generally regarded as one of the key ways to solve theproblems of the air pollution and the pinch of the energy sources all over the world.The Electric-Vehicle has got a rapid development recent years. Due to its low costsand high reliability, the Valve Regulated Lead Acid (VRLA) batteries still remain thekey position in applications for Electric-Vehicles. In this dissertation, thecharacteristics of VRLA batteries used to power Electric-Vehicles are discussed firstly.The failure modes, charge algorithms, also with the significant changes in VRLAbatteries design are discussed in detail. This dissertation mainly focuses on the batterymanagement for (VRLA) batteries for Electric-Vehicle applications. In general, abattery management system may include the main charging system, the equalizingcharging system, and the battery state detecting system, etc.The Pulse charging/discharging method is adopted as the main charging algorithm.This charging algorithm is achieved based on a bi-directional full-bridge DC/DCconverter. The power rating of the main charger is about 20kW. With serialconnection, imbalance may happen among the operating battery units during ethercharging or discharge. Here an equalizing charging system is designed to keep batteryequalization during charging. This system includes of a switch module, an auxiliarycharger and a control circuit. A new ZVS active clamp forward converter is adopted toserve as the auxiliary charger, where by employing a simple auxiliary LC network, themain switch is able to achieve ZVS. Experimental results show that about 2% higheroverall efficiency is obtained in the prototype converter than in its conventionalcounterpart.The battery state detecting system measures the voltage and temperature of thebatteries, then it estimations the state of charge (SoC) and state of health (SoH). A,novel method used for estimation of SoC is proposed, which is based on AH principle,Peukert equation, temperature correction, SoH and open-circuit-voltage.
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