High-voltage batteries are of central importance for electric vehicles as an energy source. Their temperature behaviour must be studied in detail and temperature models must be verified. The new HV DTemp measurement system enables temperature measurements within high-voltage batteries in a completely new dimension.
Temperature measurements in the development of high-voltage batteries place special demands on the required number of temperature sensors, their exact positioning and the measurement accuracy. The solutions available to date quickly reach the limits of what is feasible.
The characterisation of HV batteries includes the analysis of the thermal behaviour of the individual battery cells and the entire battery assembly. To verify the temperature behaviour of a high-voltage battery prototype, precise temperature measurements during operation of the HV battery at several points between battery cells are therefore necessary to measure the temperature profile at cell level. Different measurement points between the individual battery cells must also be placed to detect hot and cold spots, which may be caused by the design geometry, mechanical stress or the cooling system.
The exact knowledge of temperature distribution and thermodynamics down to the cell level allows the validation of simulation models and the optimization of battery systems.
The most accurate temperature model of a HV battery is necessary during many production steps of vehicles and charging systems in order to control the corresponding procedures during vehicle operation (calculation of the charging process or the cooling capacity). How precisely the temperature model represents the HV battery is determined by the most accurate verification possible.
The CSM HV DTemp measurement system is designed for the digital and precise measurement of up to 512 temperature measurement points via a single cable connection to the HV DTemp central unit. A HV DTemp measurement system consists of the three components HV DTemp-4 Sensor Modules, HV DTemp-M64 Controller Modules and HV DTemp-P Central Unit.
Up to four IC (Integrated Circuit) temperature sensors are connected via digital bus to an HV DTemp-4 Sensor Module. The sensors are arranged individually on a ultra-thin flexible circuit film, or together on one film. The sensor size is in the mm range (W×D×H: 1.5 mm × 1 mm × 0.5 mm). The flexible circuit film design and the sensor position can be determined according to the application and customer-specific requirements. The ultra-thin flexible circuit film itself has a thickness of less than 0.8 mm. The SMD mounting of the temperature sensors on the film ensures exact transmission of the geometric arrangement of the temperature measurement points from the simulation. The ultra-thin flexible circuit film has geometric features that makes it easy to precisely align it with the cell of the HV battery, thus ensuring simple and accurate mounting of the temperature measurement points.
The HV DTemp-4 Sensor Modules are connected to a HV DTemp-M64 Controller Module. The HV DTemp-M64 Controller Module provides the addressing, power supply of the sensors and transmission of the temperature values to the HV DTemp-P Central Unit. The HV DTemp-M64 Controller Modules are very small (W×D×H: 48 mm × 87 mm × 0,75 mm) and can be installed inside the HV battery housing to save space. They offer connections for up to 16 HV DTemp-4 Sensor Modules, i.e. for up to 64 IC temperature sensors. Up to 8 HV DTemp-M64 Controller Modules can be easily cascaded. Thus 8 Controller Modules with 64 temperature sensors provides a maximum of 512 temperature sensors enabling a very thorough understanding of the battery thermal behavior.
The HV DTemp-P Central Unit, to which the HV DTemp-M64 Controller Modules are connected via a touch-proof high-voltage connection cable (8 wires, Ø 8 mm), is located outside the HV battery. The HV DTemp-P Central Unit has two galvanically isolated inputs. Thus, temperatures from within two different high-voltage environments can be acquired. The 512 measurement points and HV DTemp-M64 Controller Modules can be divided between the two inputs. The communication of the HV DTemp-P Central Unit with the external measurement computer for the configuration of the measurement system and for data acquisition is done via CAN bus. Each measurement point is assigned its own CAN-ID, documented in a DBC description file. The temperature sensors can thus be clearly assigned and identified. The data transmission on the CAN bus is potential-free in "free running" mode.
The layout of the ultra-thin flexible circuit film with digital temperature sensors can be tailored to the exact requirements of the measurement point arrangement within the high-voltage battery, individual cell modules, and between cells. The IC temperature sensors can also be used individually by connection cables in practically any desired arrangement. This allows very accurate measurements of temperature distribution, temperature paths, temperature profiles or hot spot areas.
For the application, the layout and arrangement of the IC temperature sensors are planned project-specifically in cooperation with CSM when several temperature sensors are to be arranged together on a flexible circuit film. The exact design of the film ensures a good and easy reproducibility of the arrangement from cell to cell.
Due to the low height of the HV DTemp-4 Sensor Modules, they can be pressed directly between the battery cells in the desired arrangement - therefore, including the ultra-thin flexible circuit film in the battery assembly process is possible.
In contrast to analog sensors, possible changes in the measured values due to interference on the measurement cables do not occur because the measured values are immediately and digitally transmitted from the sensor. In the worst case, of extreme interferences, no measured values are transmitted for a short time. As soon as these interferences have subsided, the system automatically resumes proper operation. The maximum measurement range is up to 125°C. The resolution of the measured values is 16-bit.