Research On Battery Management System In Portable Instruments

This paper takes the research and development of portable instruments as background and researches into the applications and realization methods of power supply batteries and battery management system in portable instruments.Through analyse and discussion,this paper gives the methold of power supply batteries selection in portable instruments.According to the demand of a portable instruments,this paper achieves the power supply batteries selection and designs its battery management system.At last,the function of this battery management system was validated through lots of experiments.The power supply of portable instruments must be batteries.Rechargable battery is very convenient for using and its electrical performance can meet the demand of application of portable instruments faultlessly.So, the rechargable battery is the perfect power supply for portable instruments.Now,the main rechargable batteries are Lead-Acid battery,Ni-Cd battery,Ni-MH battery,Lithium-ion battery and Ploymer Lithium-ion battery.Because there are many differences of characteristic during those batteries,the selection of power supply battery is vital for portable instruments.During the process of power supply battery selection, many factors must be considered,such as single battery voltage, single battery capacity,the max discharge current,charge mode, the max charge current,energy density,power density,life-span,auto-discharge rate,volume,weight,security,p- ollution,memory effect,cost,technology maturity degree etc.The above factors must be considered roundly according to the demands and application occasion,especially the electrical factors.Through analysing the characteristics of all kinds batteries,we can give the appropriate power supply battery.According to the actual application demand,this paper selects Lithium-ion battery as power supply for instrument.In order to improve the performance of batteries and instrument, comprehensive protection and management shoule be applied to power supply batteries.The designed battery management system in this paper combine distributed BMS with centralized BMS.The main modules of this BMS are the main and assistant power switching module, power module,MCU module,charge management module,battery information sampling module,discharge management module,protecti- ng module,charge balancing module,SOC forcasting module,communication module etc.According to the application demand of instrument in this thesis,this paper adopts inductance charge balancing methold aiming to achieve charge balancing during single battery.In order to reach 3% SOC forcasting precision,this paper combines open voltage methold with ampere-hour methold to forcast SOC of battery package.Through a lot of experiments,the charge and discharge performance of designed battery package are well.The designed battery management system works well and all function modules achieve the anticipative objects.The SOC forcasting precision is 1.1%,meeting the application demand.The battery management system improves the security,charge efficiency,discharge efficiency,cycle life-span,stability and reliability.The above factors improve the whole performance of instrument.