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HIL Tests for Battery Management Systems

Emulating battery cell voltages

Application Areas

  • Vehicle traction battery
  • Stationary storage systems
  • HIL test for battery management systems (BMS)
  • Simulation of high-voltage batteries at cell level
  • Real-time multicell battery simulation
  • Failure simulation for battery management systems
  • Lead-acid (Pb), nickel-cadmium (NiCd), nickel-metal hydride (NiMH), and lithium-ion (Li-ion) batteries

Key Points

  • Scalable, compact system supporting up to 32 cells in one 19'' 3 U subrack
  • Emulation range from 0 to 6 V
  • Accuracy of ±1.5 mV across the entire working temperature range
  • Short refresh rate of more than 1 kHz
  • Temperature simulation by means of isolated analog outputs and an advanced simulation model
  • Efficient computation of a large number of cells
  • Safety compartment for the ECU
  • 1 A of current per channel, parallel operation possible

The main task of a BMS is to balance the voltages of each cell in a multicell battery. Furthermore, it monitors the battery’s temperature continuously. For realistic tests of the BMS, at least one cell module has to be integrated into the HIL system. The cell modules measure the cell voltages and provide the connection between the ECU and the battery. The main task of the HIL simulator is to output the cell voltages and temperatures with high precision.

The EV1077 supplies continuously adjustable voltages in the range of 0 to 6 V. With this range, damaged cells can be emulated as well. For example, a voltage higher than the nominal voltage simulates a cell's increased internal resistance during charging. Depending on the battery type and the test focus, several EV1077 Battery Cell Voltage Emulation Boards are combined in the HIL system. For each 32 EV1077s, one EV1082 controller board is needed that controls the cell emulation boards and communicates with the real-time system. Because one EV1077 can emulate 4 battery cells, one controller board controls up to 128 cells.

All live parts of the test system are galvanically isolated, letting you connect the modules in series up to a voltage of 1.000 V. To meet safety regulations, a safety compartment prevents accidental contact with the ECU, protecting you against harm stemming from high voltages. 

For the simulation of high-voltage batteries, a real-time-capable simulation model has to provide plausible voltages and temperatures for each cell at all times. This allows realistic tests of the balancing and thermal monitoring algorithms in the BMS. Since the batteries consist of a series of battery cells, the computation requirements can be demanding. To reduce the processing load, the dSPACE ASM Multi Cell Model (in ASM Electric Components) connects single cells of identical design to create a series string of cells. This string consists of a reference cell model that describes the basic behavior of the cell type, and a delta model that computes the deviation of each cell's voltage from the reference voltage. This approach reduces the required computation power, as the complexity of the model is independent of the number of cells. For advanced requirements even at the battery design level, new, even more detailed, models are available. 

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