Peers group's blog finding

For the peers group's blog finding we picked to describe the +E- Project post. The group is working on evaluating improvements to Battery Management System performance and costs. They studied an article named ''Balancing management system for improving Li-ion batteries capacity usage and lifespan" what we consider as a very interesting issue. 

In their project they are supposed to use the Li-ion cells with a voltage drop between 3 and 4.3 V. Below the voltage of 3 V there is a high chance of entering into a deep discharge state. The recovery time is very long. Moreover, above voltage of 4.3 V the cell may be destroyed because of the overheating. Parallel cells are self-balanced, what does not happen when they are put in series. Furthermore, the balancing methods-active and passive are being discussed. In the passive way of balancing the cells are discharged when the battery is not being used or an alternative path for the current flow is provided while it is being charged. In the active balancing methods we can highlight two main procedures- balancing with the help of capacitors or converters. The processes are based on switches in order to control cell balancing. Modularized switched capacitor method transfers energy from cell to cell on the first tier capacitors and from pack to pack on the second tier capacitors which is efficient and modular but on the same time hard to implement. Converters separate into isolated and non-isolated which are bigger and more expensive, but easier to control. What is more, it can be set apart 3 charging methods: CC-CV (constant current - constant voltage), multi-stage and pulse charge. CC-CV method has three main phases, first phase is trickle phase which is implemented when cell voltage is low. Phase two consists of a constant current power supply and phase three uses constant voltage which reduces charging current. Multi stage charging consist of having multiple stages where in each stage there is a different current. This method can vary on the currents and the conditions for changing the stage. There is also pulse charge method, most advanced and efficient, which is implemented by controlling its frequency or its duty cycle. In these methods it is possible to see that they consist of finding the best duty cycle or frequency during a searching process based on minimizing impedance and maximizing charging current. 

Source link:
https://pluse-project.blogspot.fi/