# Analysis and Synthesis of Architectures for Automotive Battery Management Systems
## 5 Methodical Approach to the Synthesis of BMS Architectures  
An E/E-architecture of an automotive BMS should be appropriate for current and future battery technologies, as many engineers and scientists expect technological changes within the next years. Possible battery technologies that are currently on the market are Lithium-ion batteries and on Nickel-metal-hydride batteries [39]. In the next few years, solid-state batteries will most probably follow [40]. Battery design will also move more and more toward highly integrated weight- and volume-optimized approaches, as described in Figure 5, using the cell-to-pack as an example. It is therefore sensible to base the synthesis of the architecture of future automotive BMSs on certain assumptions and functional requirements, which will most probably not change within the next two decades. Taking the considerations listed above, the following assumptions concerning the synthesis of the prospective BMS can be formulated:  
* The vehicle battery consists of individual cells, which are connected in series or parallel in order to provide the desired capacity and voltage level as well as charge and discharge current. * The vehicle battery may consist of sub-modules, which also consists of individual cells, which are connected in series or parallel in order to provide the desired capacity, voltage level and discharge current. The cause for these sub-modules can be geometrical (divided spaces in the vehicle for battery sub-modules), functional (e.g. redundant sub-modules) or caused by assembly considerations (e.g., sub-modules with lower voltage, which are less dangerous). * The BMS must provide protection devices for disconnecting the mains (e.g., contactors, pyro-fuse) and protection against high currents (e.g., fuses, pre-charge resistor). * The measurement of voltage, current and temperature is important, because the cells need to be operated in the safe operating area. * The BMS may also be responsible for an active regulation of the temperature of the vehicle battery; usually both a regulation of heating and cooling entities is necessary. The synthesis of E/E-architectures needs to be integrated in the overall product development processes. In the automotive industry, currently the model-based systems engineering (MBSE) [41] is employed for achieving efficient digital processes with connected product and process models [42]. The processes constitute the development life-cycle of the technical system and are usually represented in the form of a V-model--such models are, for instance, described in the guideline VDI/VDE 2206 [43]. The V-model is a graphical representation of the logical sequence of process steps [44]. Several essential elements in this sequence concern the functional domain (compare [45; 46], i.e., models of the technical system, which describe the intended functionality. The functional domain is located on the upper left side of the V (Figure 6--based on the guideline VDI/VDE 2206 [43]). One of the cornerstones of successful product development is a transparent representation and a conscious occupation with the functional domain, which requires an integrated consideration [45]. Very important are also verification and validation processes. It is important to note that both verification, i.e., evaluating whether the BMS meets the given requirements, and validation, i.e., evaluating whether the requirements correctly and entirely captures the customer's expectations, are essential. An important role in verification processes plays so-called HiL testing, i.e., a combination of real and virtual components in a simulation. Such verification processes should be conducted continuously--this leads together with complete system tests to an evolutionary development process (compare Section 2.4). As stated above, the clarification and conscious development of the functional domain may be crucial.