Another important aspect of setting up a test environment for the qualification and verification process of traction batteries is the selection and optimisation of appropriate measurement equipment. This is necessary to achieve reliable results, based on which, precise statements about the behaviour of the battery system in the later-intended application can be made. So the reaction of the DUT during a test procedure has to be recorded in a highly precise and dynamic manner. The variety of different measurement signals for a traction battery test includes the battery terminal voltage/current, the cell or module voltages/currents and temperatures at different spots. For understanding and verifying the battery behaviour under different conditions, the discrete signals have to be synchronized. Only with this synchronization, the state of the battery at certain operating points can be analysed. According to the different signal types and ranges, a suitable data acquisition system has to flexibly adapt to the specific conditions. Besides measuring the high battery terminal voltage with high precision, the instrumentation also has to guarantee the measurement of the individual “low” cell voltages with the same accuracy. Just as important as the adaptation to the different signal levels, is to ensure that the huge number of different signals can be recorded simultaneously. Furthermore, it is necessary to ensure online-monitoring of the signals, especially the critical signals. So in case of critical conditions or unforeseeable faults, the test staff can manually interrupt the test procedure. For further analysis and documentation of the test procedure, a simple post-process editing and evaluation should be possible.
The HBM GEN3i is especially suited for this high requirement of data acquisition and transient recording. The GEN3i data recorder enables synchronous acquisition of all important quantities in energy-related systems with a large number of channels and high sampling rates . With this data recorder, the easy commissioning of the test bench as well as the data acquisition during test procedures can be accomplished. Easy test measures like determination of capacitance as well as more complex measures like electrical impedance spectroscopy can be executed. Post process, the data can be analysed and further processed. This results in the generation of accurate statements about the battery system.
The entire instrumentation consists of:
- GEN3i data recorder for data acquisition, transient recording, live monitoring, post-process editing of: battery current/voltages/temperatures, inverter voltages/currents
- LEM IT 700/1000 S with high-precision measuring shunts, HBR 2.5/10 for measuring phase and battery currents
- Artificial star for measuring grid side voltages
- Thermocouples Type K
Figure 7 shows in a diagram format the measurement acquisition of system quantities which are sent to the GEN3i data recorder. For testing a traction battery system, only the measurement of the battery quantities is necessary. This includes the battery terminal voltage and current, the individual cell or stack voltages, as well as temperatures at different spots. However, for the commissioning of the test bench, a lot more signals have to be analyzed. For implementing and optimizing the grid control, the grid phase currents and voltages as well as the DC link voltage has to be measured. Based on the optimized grid control, the output control for charge/discharge experiments have to be set up. For this, the output converter and filter quantities have to be measured. With the dynamic measurement of the output quantities, different control strategies for the output side can be easily analyzed.