20kW VRLA Battery Management System For Electric-Vehicles

Electric-Vehicles have become the research focus of most famous carmakers all over the world because of the problems in air pollution and petrolium crisis. Due to its low costs, the Valve Regulated Lead Acid (VRLA) batteries still remain the key position in applications for Electric-Vehicles. In this dissertation, a battery intelligent management system, which includes battery state detection, equalizing management, temperature management and charge/discharge management has been proposed.The characteristics of VRLA batteries used to power Electric-Vehicles are discussed firstly. The failure modes, charge algorithms, also with the significant changes in VRLA batteries design are discussed in detail.This dissertation mainly focuses on the battery management for (VRLA) batteries in the Electric-Vehicle applications. The management system inside the car(battery state detecting system and equalizing charging system) has been discussed in detail of the chapter 3&4. The chapter 5 proposed the charge/discharge management system outside the car.The battery state detecting system measures the voltage and temperature of the batteries, 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.Here an equalizing charging system is designed to keep battery equalization during charging and discharging. The controler, switches and an auxiliary charger make up the equlizing system.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/DC converter. The power rating of the main charger is about 20kW.