Easy and robust parameterization of electric battery models using test bench data
Modern batteries for hybrid and electric vehicles need to meet high demands – such as being able to cope with high charge and discharge currents, permitting reliable calculation of the SOC (state of charge) as well as guaranteeing the greatest possible cruising range. To calculate these parameters, it is essential to have precise knowledge of the chemical processes and of the performance of sensors. IAV advocates model-based control in particular: Our experts model batteries at various levels and validate their results on the test bench.
To parameterize battery models, IAV has developed the IAV Barito tool which covers the entire workflow and forms part of the tool chain we have developed in-house for electric powertrains: Beginning with the test specification, the tool systematically guides the user through the parameterization process.
As the battery model, IAV Barito uses an equivalent electrical circuit diagram comprising an ohmic resistor and a user-definable number of series-connected RC elements. During measurement on the test bench, various load profiles at different temperatures and states of charge are fed into the battery to measure the current and voltage of cells or entire batteries. The tool pre-processes the data measured and checks them for plausibility.
Battery model in only one minute
Proceeding from the data measured, IAV Barito then calculates the internal ohmic resistance and the parameters of the RC elements as functions of temperature, SOC and direction of current. These values can be used for generating a battery model of the type required, for example, in longitudinal dynamics simulation or in battery management systems. What IAV Barito manages to do in less than a minute used to take many hours. The tool then checks the quality of the parameters, with it also being possible to use customer-specific validation methods.
Unlike the case with existing solutions based on Matlab, IAV Barito users do not need to be experts in programming or battery modeling. In the basic version, the tool consists of four modules:
- Identification (data import, identification of interpolation points and analysis)
- Validation (determining the quality of the parameter set)
- Scaling (cell, module or battery level)
- Simulation (on the basis of scaled maps)
IAV Barito is easy to work with and delivers all maps within a matter of minutes. The tool can be used in automotive SPICE and in projects relating to safety.
Typical applications for IAV Barito:
- Calibration of battery models in control units, for CFD co-simulation or for simulating vehicle longitudinal dynamics
- Battery model validation/simulation
- Checking the plausibility of cell, system and vehicle data measured
- Analyzing the aging behavior of model parameters, among others
- Comparing different equivalent battery circuit diagrams
You are very welcome to get in touch with IAV Barito free of charge and without obligation.