Control strategies for charging and discharging policies of rechargeable batteries

The rechargeable batteries will play a more and more important role in the future. This is because they can make a great contribution to many areas. Like for example the efficiency of the performance, the need for energy conservation, environment protection and so on. As a result, Li-ion battery will finally become a leading candidate for the next generation rechargeable batteries. However, there are still some difficulties in making full use of Li-ion battery. This report is focused on the challenge of the control strategies for charging and discharging policies of Li-ion battery. Firstly, to compare the effects of charging and discharging policies. Actually there are many kinds of Electrical model can be used. Then a suitable Li-ion battery Electrical model is proposed[1]. Secondly, for the complete battery system, it consists of three parts: protection, management and balancing. Among these three parts, cell balancing is the most important part, as without the balancing system, the individual cell voltage will float away over time. Therefore, we need to choose a good cell balancing method. There are many cell balancing methods and they all have their own advantages and disadvantages. For example we can connect a resistor in parallel with the battery who has a higher initial state of charge (further explanation of the state of charge will be given later). We can use converter and transformer to do the cell balancing as well. During the charging and discharging process. There are some factors (differences in chemical characteristics, temperature, internal resistance) affecting the cell remaining capacity. As a result it may lead to overcharging and over discharging, this may decrease the cell storage capacity; shorten the battery lifetime and eventually, permanent damage to the cells. The main function of the cell balancing is to make the individual cells difference (especially state of charge) get smaller and smaller. This report conducts cell balancing by using two method Lastly, the simulation results show out the excellent control effect of the strategy. Then, the conclusion of this report and the recommendations for future work will be given as well.Bachelor of Engineerin