It could be shown that the costs and size of a battery for public buses can be significantly reduced by using a smaller battery and fast charging every other round. The consequently smaller maximum driving range due to the smaller energy capacity does not limit the operation ability of the vehicle as the charging breaks are relatively short and can be done at the final stop of the vehicle. By recharging every round the charging time could even be reduced to less than ten minutes. Moreover, the charging time can be used at least as a small buffer time in operation for slight delays. With this approach electric mobility might in the future not only be a nice to have option for public transportation due to its local emission-free operation but competitive to diesel fuel driven buses that are nowadays state of the art. Contrary to private electric mobility the cycle life of the battery can completely be exploited and therefore a higher cost efficiency is achievable. The cells for a mobile battery system in general have to be chosen based on the estimated driving range, the needed load factors and the actually usable cycles. All of these determining factors are known in detail for public buses. Therefore, it is possible to choose the optimal cell for the respective application and to decide on a fundamental system structure. In the system structure especially the reliability of the system should be taken into account due to safety reasons. The design steps in the system design can be divided in mechanical and electrical ones. Mechanical issues are the stabilization of the cells as especially pouch cells are quite flexible and the crash safety. It was shown exemplarily in the project Smart Wheels how this can be realized in a conversion design vehicle. Especially the housing could be realized lighter for a purpose design vehicle and also the cell alignment m modules could be modified for a more flexible construction space. Electrical issues are the insulation for electric safety and the management system that is usually divided in a master-slave architecture, which can include a fall back level. Regarding the measurements it can be stated that the voltage measurement of every single cell in a series connection is inevitable, whereas it is possible - depending on the architecture - to monitor not all temperatures in a module. For the temperature monitoring in series production it is also imaginable to combine the actual measurement of temperatures, that is needed for the load management, with bimetall switches that shut down the pack independently by a safety circuit in case of an overtemperature. This would lead to only a few temperature sensors per pack and therefore reduced costs. The positioning and needed amount of sensors can be simulated beforehand. For the thermal management it could be shown that there are driving applications such as fast charge where cooling is mandatory. Therefore, a liquid cooling system in the ground plate was designed and taken into operation. A possibility to connect the cells to the cooling system was given by the aluminum plates. With the designed cooling system it was possible to reduce the temperature gradient within the pack and the cells below 2.5 °C which is of great importance for an even aging of the pack. Still, further cooling concepts such as a direct cooling of the contacts can be considered to reduce the overall weight of the system.


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    Title :

    HV traction battery: From layout to realization


    Contributors:
    Rothgang, S. (author) / Lunz, B. (author) / Laresgoiti, I. (author) / Geulen, G. (author) / Homann, J. (author) / Töpler, F. (author) / Gehrmann, S. (author) / Eckstein, L. (author) / Sauer, D.U. (author)


    Publication date :

    2012


    Size :

    10 Seiten, 12 Bilder, 1 Tabelle, 9 Quellen



    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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