# Battery Management System Hardware Concepts: An Overview
## 7 Conclusions  
This work presented an overview of common concepts for BMS hardware, starting with a collection of generic requirements, for which, later on, implementation considerations are presented. As shown in Section 2, it is important for a design process to include as many parameters as possible. However, the requirements should be set up according to the target device's needs: a small electric device for medical implantation most certainly has a different requirement list than a battery system designed for an aviation use case. The given thoughts about the requirement set should be a good starting point for any battery pack design considerations. Section 3 has shown how the battery system's structure impacts the BMS topology. Examples were cited, where the application dictated comparatively unusual approaches in terms of monitoring in favour of reducing weight or complexity. In Section 3.3, four commercial EV batteries were shown and compared. It could be seen that several commonalities resulted from the similar application, e.g., the use of CAN for communicating to the vehicle. Interesting were the differences in integration efforts and BMS internal communication, having the extreme cases of the VW e-Up's central BMS module with resulting high wiring efforts as opposed to the highly integrated smart battery in mind. Section 4 has provided details on the implementation of acquisition of needed physical values and how to transmit them. For most measurement needs, there are different approaches that will have to be selected with the individual application's constraints and needs in mind. Application and production related causes for charge imbalance between serially connected battery cells and different ways that are available to compensate their effects were described in Section 5. It can be said that, at the moment, passive balancing still seems to be the most widely-used method. Finally, Section 6 gave an overview on safety aspects. The compliance with the defined operating ranges of the adopted battery cells to ensure a long lifespan, as well as keeping the user safe from potential harms resulting from high voltage, were identified as key issues. State-of-the-art approaches to insulation monitoring were described, showing that the standardized configuration for insulation monitoring consists of a voltage measurement, a simple switch and a well known resistor to indicate the insulation resistance. It was mentioned, however, that also dangers that can occur on the system level have to be considered, when the battery is shut off for the sake of its own protection. If these are potentially more harmful than e.g., a battery that has been damaged by deep discharge, but can afterwards be kept in a safe state by denying to charge it again, this might be the lesser evil. In conclusion, an overview of state-of-the-art BMS implementation approaches has been given. The authors tried to highlight different aspects of relevance resulting from individual systems, in order to enable the reader to estimate what is necessary to design a BMS for a given system. However, it has to be said that, due to the huge variety of applications and systems, it is not possible to consider every single existing facet. For the future, the authors expect a continuous improvement of available BMS components. In addition, several interesting approaches regarding new concepts for BMS implementations exist, like fine grained modularization and different means of communication, as in [85] or [86]. In addition, regarding robustness and failure detection, there are still new ideas emerging, see, e.g., [67]. Another aspect with rising significance might be the integration of BMS functionality into the battery cell, as, e.g., mentioned in [41; 85; 87]. For large battery cells or special operating conditions, this approach could provide advantages by allowing easier assembly of packs, as well as more sophisticated monitoring of cell internal parameters.