Li-ion battery characterisation, modelling and battery management system design

Energy has always been one of the most valuable thing in the World. After the invention of machines that sometimes facilitates human life or sometimes takes all charge of human works, the energy concept is getting more and more attention in these days. Moreover the absence of energy makes the people feels like they are living in one or two era before. The energy concept expecially electrical energy concept became a vital for human life but this concepts brings some other complaints like cable complexity or cable depency. Because of these issues wireless energy transfer concepts and energy storage concepts are being worked on nearly since the invention of electricity. The main topic of this thesis is chemical energy storage systems, batteries and also safe and efficient operating ways of these batteries. A glance at the improvement of battery industry, invention steps and types of batteries takes places alongside with the survey on today's battery types and their safe operating regions, advantages, disadvantages and especially lithium ion battery specifications and its requirements, in this thesis. The modelling of lithium ion battery for efficient usage in appropriate conditions, to make an infrastructure for gauge algorithm and to take protection precautions via "battery management system" design, analysing the results of different conditioned battery cycle tests and getting the parameters of battery model, embedding these parameters and battery models in battery management system's microcontroller construct the main steps of this theses. The first topic in this theses will be the origin of battery and battery needs of human. The ancient battery which found while the train rail installation, belongs to Babilon Empire times. An also the near time history of batteries which are founded by Volta is one of the topic in history of batteries. After the history of battery, modern battery types and their power density levels, usage properties, use cases has been mentioned in this thesis. Use cases also includes the topics of "which battery needs what" type data. The battery stacking properties, ambient temperature properties, maximum working temperature, minimum working temperature, maximum charge voltage, minimum charge voltage, minimum charge current and maximum charge current properties creates the basic battery management system spects. Moreover of these properties, the prediction of battery capacity and prediction of battery health condition are makes the battery management system, more reliable, more useful, more resourceful. Because these extra features comes with more efficiency of battery, more safety of battery. "The prediction" word is actually related to getting restricted information from somewhere that we couldn't get or measure the all information in control theory. These restricted info becomes input of some mathematical models and the outputs of this model will be the data that we couldn't measure or get from system. Thats why the main part ot this thesis is modelling the battery. Battery modelling is used for getting right information about battery remaining capacity, remaining working time and also full capacity of battery without making full charge and full discharge the battery. And also the modelling of battery comes with the information about battery health condition. The battery health related to two main things, one of them is internal resistance change (increase) of battery, other one is the change of battery capacitance in the predefined time period. The state of health data and state of charge data need to battery modelling. Extracting the battery model parameters from real battery is based on battery discharge tests in different ambient temperature and different discharge currents. In this thesis total 25 discharge tests are performed and all parameter data collected. These parameters evaluated by 6Sigma -statistical control tool- regression analyses with "Minitab" and "Reliasoft" pc softwares. Analyses includes model factors selection and model factors reduction for simple modelling. The protection of battery and the prediction of battery functions establish the battery management system. Even some battery management systems includes other functions, the fundamental spects are these two and this thesis covers these topics detailed. When we looked from a wide angle, battery management systems also includes arrangement serial or parallel of battery packs to establish more powerful battery units. The communication protocols, communication types, connection types, connection arrangements, fail safe operation algorithms, master-slave organisation and their duty sharing is also the topics of this thesis in the battery management system point of view. At the end of thesis work, the last topic is designing the battery management system hardware and software. Different, dedicated BMS ICs which are Texas Instruments Bq76930 and Intersil ISL94202, are used in this phase. For different type of communication topology, two types of hardware with Texas Instruments Bq76930 and one type of ISL94202 hardware, totally three different types of battery management system hardware and software that includes proposed battery model are designed in this thesis. As a result of all works in this thesis, history of battery, types of battery chemicals and their usage, protection, power density requirements, the effects on human health topics are mentioned. After these topics, battery management system requirements mentioned for lithium ion type batteries, for example, voltage protections, current protections, temperature protections etc. battery management system general system topologies like central BMS, master-slave configured BMS etc. mentioned in battery management system topologies header. Beside the battery management system topologies, also battery balancing systems an their topologies mentioned in two main header; active balancing and passive balancing. Also their subcategory topologies mentioned in detail in this thesis work. All these headers actually creates literature research. In literature research, another header is battery modelling requirement for state of health estimation and their simulated electronic circuit topologies. More than one topologies are merged and suggested a new model in this thesis work that includes ambient temperature effects and discharge current effects. So that, suggested new model became more robust and more flexible for different types of ambient condition and load condition of battery pack. This new suggested model also coded in battery management systems microcontroller and got the results of these model output as estimated battery cell and battery pack voltage. As a result of all these thesis work, complete battery management system hardware, software, battery model that acts like infrastructure of state of health estimation.