Testing the EV Battery Pack: Theory and ART Logics Solutions

Electric Vehicle (EV) battery packs are complex systems composed of multiple layers of energy storage and control. At the most granular level are the battery cells—individual units capable of storing and delivering electrical energy. These cells are grouped into modules to increase voltage and energy capacity. Modules are then assembled into complete battery packs, capable of reaching system voltages as high as 800V for modern EVs, compared to the older 48V standard.

To ensure safety, longevity, and performance, battery packs are equipped with a Battery Management System (BMS). The BMS monitors the state of each cell and module, gathering critical data from voltage taps and temperature sensors. A busbar with voltage and temperature sensing elements interfaces with the cells, relaying data to a Battery Management Unit (BMU). The BMU interprets this information, processes inputs such as vehicle speed or crash sensors, and calculates key parameters: State of Charge (SOC), State of Health (SOH), driving range, and thermal warnings.

Understanding Battery Pack Testing: Cell Testing vs. BMS Function Testing

In the context of electric vehicle (EV) development and validation, battery pack testing is a fundamental step to ensure performance, safety, and reliability. However, battery pack systems consist of two major components that require entirely different approaches to testing:

1. Battery Cells (Single, Module, and Pack Level)

2. Busbar and Battery Management System (BMS)

Part 1: Testing Battery Cells and Battery Packs

Battery cells, whether tested individually, grouped as modules, or integrated into a full battery pack, undergo one main type of test: charge-discharge cycling.

✅ Purpose of Charge-Discharge Cycling:

1.Quality Control: Compare the charge-discharge curve to the manufacturer’s reference to validate cell quality.
2. Parameter Calculation: From the charge-discharge curve, calculate internal resistance, usable capacity, energy efficiency, and other electrochemical properties.
3.Endurance Testing: Repeated cycling reveals degradation over time and aging effects.

⚙ Products Used for Cell Testing:

ART Logics provides high-precision Battery Cyclers adapted for:

· Single Cell Testing: Low current (up to 10A) / Low voltage (up to 7V), high-channel count systems (up to 18 channels).

· Module Testing: Mid-voltage (up to 40~60V), higher current capability (e.g., 50A or 150A).

· Pack Testing: High voltage (up to 800V), high current (up to several hundred Amps).

Each channel can be configured for:

· Constant Current (CC)

· Constant Voltage (CV)

· Constant Power (CP)

· Constant Resistance (CR)

Charge-discharge software enables:

· Real-time data logging

· Curve comparison

· Capacity and IR analysis

· Long-term cycling plans

Part 2: Functional Testing of BMU and Busbar

The Busbar + BMU subsystem is responsible for monitoring and controlling the battery pack. This includes:

· Measuring voltage of each cell via the busbar

· Monitoring temperature sensors (NTC or analog sensors)

· Calculating:

o State of Charge (SOC)

o State of Health (SOH)

o Thermal status

o Remaining Driving Range

It also processes external vehicle signals:

· Analog Inputs: e.g., pedal sensors

· Digital Inputs: e.g., ignition or crash sensor

· Frequency Inputs: e.g., PWM signals

· Bus Communication: e.g., CAN, LIN from VCU

⚙ Products for BMS Functional Testing:

To test BMS systems outside of the battery pack, ART Logics offers:

1. Cell Simulation Module

o Simulates each cell voltage independently (0-5V adjustable)

o Up to 256 channels per rack

o High-speed DACs for accurate, real-time control

o Ideal for emulating a full pack without real cells

2. NTC Temperature Sensor Simulator

o Emulates up to 144 NTCs

o Programmable temperature value output

o Accurate resistance simulation matching thermistor curves

3. BMS Function Box

o Simulates all external signals for the BMU

o Includes:

§ PWM input generation

§ Analog/Digital inputs

§ CAN communication handling

§ Fault signal simulation

o Acts as an HIL platform for real-world validation

Why Two Separate Test Systems Are Needed

Test Target	Test Method	Products	Real Cells Needed?
Cells / Modules / Packs	Charge-Discharge Cycling	Battery Cyclers	✅ Yes
Busbar + BMS	Functional Simulation	Cell Simulator, NTC Simulator, Function Box	❌ No

· ❌ You cannot test the BMS while cells are disconnected unless you simulate them.

· ❌ You cannot properly test the cells if the BMS is interfering or limiting the operation.

By separating the two testing approaches, engineers gain:

· ✅ Flexibility in testing abnormal cases

· ✅ Accurate measurement and control

· ✅ Repeatability and speed

After Final Pack Assembly: Full System Testing

Once the battery pack is fully assembled with:

· All cells connected

· Busbar and BMU integrated

The BMU becomes the sole interface to get internal battery information. The user communicates with it through:

· CAN bus

· XCP/UDS protocols

The final test consists of:

· Full pack charge/discharge using high-power cyclers

· Reading back state values from the BMS

ART Logics Testing Solutions by Battery Pack Component

1. Cell-Level Testing

At the cell level, ART Logics offers multi-channel battery cyclers capable of precise charge/discharge cycles. Each channel supports configurable cycling profiles: Constant Voltage (CV), Constant Current (CC), Constant Resistance (CR), and Constant Power (CP). Our 18-channel Battery Cycler (BC-18-7-10) supports voltages up to 7V and currents up to 10A per channel. It allows simultaneous independent cycling of each cell, ideal for laboratory qualification or production-line QA of battery cells.

2. Module-Level Testing

Modules—groups of cells—require more power during testing. ART Logics provides high-power cyclers with voltage ranges up to 50V and current capabilities exceeding 50A or 150A. These solutions enable full-cycle testing of module behavior under charge/discharge stress, verifying thermal consistency, balance management, and safety.

3. Pack-Level Testing

For complete pack validation, ART Logics develops high-voltage battery pack cyclers that support hundreds of volts and high current levels. These systems simulate real-world load conditions and enable complete discharge, fast-charging simulation, thermal behavior, and dynamic stress testing.

4. Busbar & Temperature Sensor Simulation

To test the BMS without needing a full battery pack, ART Logics offers Cell Simulation Modules and NTC Sensor Simulators. The 18-channel Cell Simulator Rack Module allows users to simulate the voltage output of battery cells to the busbar. Our NTC Simulator (NTC-4-1-7M) emulates temperature sensor outputs, enabling safety systems and temperature monitoring validations.

Cell simulation rack and NTC simulation modules

5. Full BMS Testing

The Standard BMS Function Box Rack (BMS-100-0) is ART Logics’ all-in-one platform for BMS functional testing. It enables validation of BMS CAN communication, data processing accuracy, trigger inputs (e.g., crash detection), and output responses under simulated cell conditions. This system is designed for both development and production-line testing, providing a complete testbench for BMS quality assurance.

Conclusion

Through this complete ecosystem of simulation and testing tools, ART Logics supports every stage of EV battery development and production. From precision cell cyclers to full BMS simulators, our platform enables faster development, better safety validation, and more robust electric vehicles.