Each cell channel circuit must be electrically isolated (typically >1000V) so channels can be stacked in series to form pack-level voltages without shorting.
BMS hardware-level design
Battery Emulator Circuit
A battery emulator circuit uses high-speed analog control loops and galvanic isolation to safely replicate battery cell characteristics, series stacking, and active BMS balancing conditions on test benches.
- Independent galvanic isolation per cell channel
- Bidirectional active source/sink current loops
- Integrated physical relay fault simulation
Short answer: a battery emulator circuit must mimic series-stacked battery cells. To do this safely, it requires independent channel isolation, bidirectional current flow to support BMS active/passive balancing, and high-speed closed-loop control. It is typically controlled by specialized battery simulator software on automated benches.
Working Principles
Core Parts of a Battery Emulation Circuit
Industrial battery emulation requires far more than a standard DC power supply circuit. It demands four key architectural pillars.
An active power op-amp design allows the circuit to output current (source) or absorb current (sink) during BMS active and passive balancing cycles.
Integrated micro-relays in the circuit simulate line faults (open wire) and polarity faults (reverse connection) to trigger BMS protection code.
Parameters
Key Specifications for Circuit Performance
| Parameter | Why it matters | BMS testing impact |
|---|---|---|
| Isolation voltage | Determines how many cell circuits can be safely stacked in series. | Crucial for high-voltage EV packs (up to 1000V+). |
| Transient response | How fast the voltage recovers when current load changes. | Simulates dynamic pulses and internal resistance drop. |
| Sinking capability | The amount of current the circuit can absorb. | Supports passive bypass balancing or active charge shuttle. |
| Voltage resolution | The smallest voltage adjustment the DAC circuit can resolve. | Required for highly accurate cell calibration testing (16-bit or higher). |
FaithTech hardware
Industrial Modular Test Circuits
Dense 12-36 channel isolated circuits designed for multi-channel cell validation and production test lines.
High-current (+/-10A) bidirectional source/sink circuits to validate active balancing systems.
Combines isolated emulator circuits with temperature sensors, communication cards, and software automation.
FAQ
Battery Emulator Circuit FAQ
Why can't I use a regular power supply circuit for BMS testing?
Standard power supplies cannot be stacked in series safely because their negative terminals are usually tied to earth ground. A battery emulator circuit uses floating isolated outputs to allow stacking and bidirectional flow.
What is the difference between active and passive balancing in circuits?
Passive balancing dissipates excess cell energy through resistors, requiring the emulator to sink small currents. Active balancing shuttles charge between cells, requiring the simulator circuit to handle bidirectional current (sourcing and sinking) on adjacent channels.
How is transient response measured in these circuits?
It is measured by applying a step change in load current (e.g., from 0A to 1A) and timing how long it takes the cell circuit voltage to stabilize within millivolts of its target.
Which FaithTech circuits should I evaluate?
Review the FT8330 or FT8331 for standard passive BMS testing, and the FT8340 or FT8350 series for bidirectional active balancing requirements.
Related guides
Related Emulation Topics
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