Battery Management System For EV Based On Active And Passive Energy Balance Strategy

In the market of automotive,where energy and environmental issues have always limited the development and promotion of electric vehicles industry.In recent years,EV with Lithium batteries as a source of energy has gained recognition of people successfully.It could provide solutions of energy scarcity and environmental degradation.But in the development and promotion of EV,there are still some technical difficulties of Li-ion battery and management system need be solved.Lithium-ion battery as a energy source affected deeply by external influences,It hard to ensure efficiency in practical applications without a smart battery management system.This paper takes lithium battery as the research object to study the equilibrium strategy for electric vehicle.Main tasks include: Research and development of SOC estimation,design of battery management system with hardware,thermal simulation of monomer battery.The ultimate goal is to improve the condition of the batteries at low temperatures.At present,there are two kinds of equilibrium circuits commonly used in the industry:energy dissipation type and energy transfer type.Passive energy dissipation balance circuit has a simple structure and low cost.Under low temperature environment,neither of them could provide an accurate and valid management.As the needs of complex working conditions,a strategy couple two kinks of balance circuits has been raise in this paper,so as to state characteristics of Li-ion battery.System selects a suitable equilibrium circuit under the control of transistors from outside control circuit acted by IC.While it working in passive balance mode,the internal thermal will increase temperature of packs.As the temperature rise,SOC of battery will be estimate more accurate.The ultimate goal is to improve the discharge capability of battery packs.In this article,through simulation to get the surface of the lithium battery and the internal temperature distribution and circumstances of the laboratory experiments of 18650 lithium batteries,comparing the measured data to validate the rationality of the simulation results,the correctness and accuracy,and to guide the discharge wire in the battery management system and passive energy dissipation balanced loss resistance in the circuit.