# Analysis and Synthesis of Architectures for Automotive Battery Management Systems
## 4 Analysis of Centralized BMS Architectures
### Common and Additional BMS Functions  
Accordingly, the Master unit of the BMS calculates states such as the SOC. This exercise can be fulfilled by using various approaches. In Lithium-Ion battery cell systems, the SOC can be estimated by the cell voltage measurements, due to the drop of the cell voltage over the discharging process. Many modern BMS's need to be more precise to obtain exact state calculations and therefore use methods such as the coulomb counting. Using this technique, the in-rushing as well as the out-rushing current becomes integrated over time to receive the actual capacity of the battery. The coulomb counting requires at least one precise current sensor in the HV-line. As shown in [8], there are multiple other estimation methods for the SOC with different accuracies and difficulty levels of implementation. Depending on the method, intensive calculation processes are needed. Being able to calculate the states on a high-performance computing unit or a powerful domain is helpful at this point. Similarly, the states of the BMS can be combined with additional information to achieve exact vehicle range prediction and health analyses of the battery cells. Velocities, accelerations, geographical topology data, environmental temperatures and other data can be collected on the PD and used for calculations. In addition, not only the BMS functions might benefit from a central computing unit. Since effective techniques of firefighting burning EVs is still limited, an early prediction about critical thermal states is essential. In order to prevent a fire in the battery and therefore in public or private places, a communication to third parties such as central fire detection systems and the BMS is helpful. Such systems can alarm responsible persons by giving them important information about critical states and the precise position of the vehicle. The implementation of such features might refer to a sub-unit, where the BMS could process and send information in an offline mode without the need to start-up the whole centralized computing unit (e.g., PD). Danger is usually large while charging a BEV. The central computer or parts of it must be online while charging because the BMS and charger need to communicate. Sending data is possible without any problems so that temperatures, voltages, currents and other important states such as the SOC can be sent via a wireless communication system. The battery junction box is often integrated into the battery box and also connected to the BMS directly. Another approach by centralizing different systems such as the BMS on one specific unit could be made by putting the junction box and the BMS together into the power electronics box. The whole PD hardware and functionality could be located in that box, which is located close to the battery cells. The main function of the power electronics today is to turn the DC current, which is coming from the battery into AC current to supply the electric motor with power. For recuperation, the process can be inverted and the battery is then supplied with power. It also changes the frequency of AC currents and needs to convert DC voltages up and down. Overall, the power electronic controls the energy flowsand is therefore instrumental in the safe operation of the vehicle. Therefore, it makes sense that the power electronics also have access to the main parts of the battery when needed. Beside charging, AC/DC-conversion, and DC/DC-conversion, also parts of the junction box and the master unit of the BMS, could be implemented in the PD box. HV-contactors and fuses in the power electronics prevent the battery from further electrical faults directly. Thermal problems can arise along the HV-lines if those components are located wrong. These components need to remain in proximity to the battery cells.