Despite the battery cells itself, the electronics, especially sensors make about 10 % of the system costs and volume in automotive applications. As the cell price and volume is decreasing, the amount of cells will increase within a Battery Electric Vehicle (BEV). Accordingly the number of monitored cells increases as there is often a 100 % monitoring rate in regard to li-ion battery systems (BS) due to safety reasons. This means that each cell is employed with a voltage sensor and each stack with a current sensor, or if a balancing system is employed, there might be an additional current sensor for each cell. With a stack as big as 12 cells, this means 13 or even 24 (if a balancing system is employed) sensors per stack. The number of sensors increases when taking temperature sensors into account. The newly developed sensor minimal battery observer allows decreasing this number of voltage and current sensors by 90 % down to two sensors per stack by keeping up the 100 % monitoring rate. This means that the presented system affords only two sensors to monitor 12 battery cells individually. This remarkable decrease of the number of sensors leads to a commensurate decrease of costs, weight and volume. Despite the reduction of sensors, it means a decrease of cables and assembling as well as construction costs. In addition to the sensor minimal observer system the system includes a cell balancing opportunity, which makes additional systems abdicable. This balancing system ensures an equivalent energy level in all associated cells to allow maximal energy output and extended service live. The service live can be extended to five times the service live of an unbalanced system for automotive application (end of life capacity 80 %). Concomitant the traction range is increased well after a few recharges due to the application of balancing systems.
Autor: Philip Dost
Co-Autor: Constantinos Sourkounis
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