Unidirectional Battery Cell Simulators

Unidirectional battery cell simulators replace real battery cells with precisely controlled electronic channels that provide defined cell voltages and source current to a device under test (DUT). Unlike bidirectional systems, they do not absorb current returned by the DUT. They are therefore particularly suitable for stable and reproducible BMS, CMS, and AFE testing where active balancing or energy flow back to the simulator is not required.

The ET System portfolio includes the N83624 with 24 channels and optional fault simulation, the compact N8330 with 24 isolated outputs, the N8331 for BMS and HIL testing, and the N8336 with up to 16 isolated channels. These systems provide high channel density and precise voltage control for simulating individual cells, battery modules, and complete cell stacks.

Typical applications include validating cell-voltage measurement, passive balancing, overvoltage and undervoltage detection, AFE inputs, leakage-current behavior, diagnostic functions, and automated end-of-line testing. The appropriate unidirectional battery cell simulator is selected according to channel count, voltage, current and power per channel, isolation, accuracy, voltage stability, dynamic response, synchronization, fault simulation, interfaces, and mechanical integration.

How to Select a Unidirectional Battery Cell Simulator

Selecting a suitable unidirectional battery cell simulator starts with the electrical architecture of the battery management system and the number of cells that must be simulated. Before choosing a system, confirm that the DUT does not return current to the simulator. The channel count, voltage, source current, isolation, accuracy, dynamic response, fault simulation, and automation interfaces should then be evaluated.

• Required current direction: A unidirectional simulator supplies current but does not actively absorb current returned by the DUT. It is suitable for cell-voltage measurement, monitoring, passive balancing, and standard BMS input testing. If the DUT uses active balancing or returns energy to the simulated cells, a bidirectional battery cell simulator is required.
• Number of channels: Define how many cells must be simulated simultaneously. The N8336 provides up to 16 channels, while the N83624, N8330, and N8331 provide high-density configurations with 24 channels.
• Voltage, current, and power per channel: Define the required cell-voltage range, source current, and output power for each channel. Consider the normal cell-voltage range as well as overvoltage, undervoltage, startup, and diagnostic test conditions.
• Channel isolation and series connection: Check whether every channel is galvanically isolated and whether the channels can be connected in series. Verify the maximum permissible channel-to-channel voltage, channel-to-ground voltage, and total voltage of the simulated battery stack.
• Accuracy, resolution, and stability: Verify programming and measurement accuracy, voltage and current resolution, temperature drift, long-term stability, ripple, and noise. The simulator should provide sufficient accuracy for the measurement thresholds and diagnostic limits of the BMS or AFE being tested.
• Voltage regulation under load: Check how accurately the programmed cell voltage is maintained when the DUT current changes. Output impedance, load regulation, settling behavior, and available current reserve can affect the simulated cell voltage.
• Dynamic response and synchronization: Check voltage response time, settling time, update rate, sequence execution, and synchronization between channels. Fast synchronized voltage changes may be required for HIL testing and dynamic battery profiles.
• Fault simulation: Define which diagnostic and safety conditions must be tested. Depending on the system, relevant functions may include open-wire simulation, short circuits, overvoltage, undervoltage, connection faults, or programmable cell-voltage sequences.
• Measurement functions: Depending on the application, integrated voltage and current measurement, leakage-current measurement, high-resolution current ranges, DVM channels, or external measurement modules may be required.
• Interfaces and automation: For automated test equipment (ATE), HIL, and end-of-line systems, verify remote-control commands, API and driver support, software compatibility, trigger inputs, synchronization, sequence functions, data logging, and communication interfaces.
• Mechanical integration: Consider channel density, rack height, installation depth, local display requirements, connectors, cooling, and integration into a 19-inch test rack. Systems without a display may be suitable for fully automated test equipment.
• Scalability: Check whether additional channels, fault-insertion modules, measurement equipment, temperature simulation, or pack-voltage simulation can be added later.
• Safety and cabling: Consider channel isolation, maximum stack voltage, protected connectors, interlocks, emergency shutdown, reverse-polarity protection, and suitable wiring for the required channel currents.

You can also view the complete range of battery cell simulators. If active balancing, charging and discharging behavior, or current flow in both directions must be simulated, explore our bidirectional battery cell simulators.

For application-specific BMS, CMS, HIL, and end-of-line test systems, ET System can combine battery cell simulators, measurement equipment, communication modules, fault insertion, safety technology, and control software through test system integration. For support with selecting a suitable configuration, contact our technical sales team.