What is a battery cycling test

1. What is a battery cycling test?

Battery Cycling Test is a process of testing the performance, durability, and performance degradation of a battery by repeatedly performing charge-rest-discharge-rest cycles under predetermined conditions. This is a fundamental testing method in the entire research, development (R&D), and evaluation process of lithium-ion batteries, especially those for electric vehicles (EV) and energy storage systems (ESS).

The battery cycling test system is responsible for precisely controlling the current, voltage, and charging/discharging times of the battery. This process can last for hundreds, thousands, or even tens of thousands of cycles to assess the changes in the battery over time.

2. The core purpose of battery cycle testing

The most important objective of battery cycling test is to determine the lifespan and stability of the battery during real-world use. Through continuous testing, engineers can collect data to comprehensively evaluate the following metrics:

• Battery Capacity: Determines the actual capacity and the rate of degradation after each cycle. A battery is generally considered satisfactory when its capacity remains at or above 80% of its original capacity.
• State of Health (SOH): Assesses the level of wear and tear and overall health of the battery over time.
• State of Charge (SOC): Checks the ability to identify and maintain the stored energy level.
• Coulombic efficiency and energy efficiency: Comparison of the energy input during charging with the energy gained during discharging.
• Load capacity and voltage stability: Evaluates performance at different current levels and monitors voltage variations throughout the cycle.
• Heat generation capability: Closely monitor the temperature of the cell, module, or battery pack during operation to ensure thermal safety.

3. Procedure for conducting a standard test cycle

A basic testing cycle always strictly follows this procedure: Charge → Rest → Discharge → Rest → Repeat .

• Charging phase: The device supplies current to the battery according to the established modes, typically Constant Current (CC) or Constant Current – ​​Constant Voltage (CC-CV). When the battery reaches its voltage limit, the system switches to sleep mode or maintains CV mode until the current drops to the specified level.
• Discharge phase: The battery is discharged with a defined current or power until it reaches the discharge cutoff voltage. This process is then repeated continuously multiple times.

4. Technical specifications require strict control.

For the test results to be practically valid, the following parameters must be controlled with absolute precision:

• Charging/Discharging Rate (C-rate): Indicates the charging/discharging rate of the battery.
• Voltage limits: Precisely set maximum charging voltage, minimum discharging voltage, charge end, and discharge end voltage thresholds to prevent the battery from operating outside its safe operating range.
• Ambient temperature: Temperature directly affects battery lifespan and performance. Therefore, batteries are often placed in temperature/humidity chambers for testing under low temperature, room temperature, or high temperature conditions to assess the impact of the environment.

5. Structuring a comprehensive testing system

A standard battery charge/discharge cycle testing system includes a combination of modern equipment:

• Battery Cycler: The core device that coordinates the supply and recovery of current during charging/discharging.
• Temperature Chamber: Maintains a stable temperature environment.
• DAQ (Data Acquisition): A system that collects data on voltage, current, temperature, and other sensor signals.
• BMS Interface: Communicates with the battery management system for module or battery pack level testing.
• Safety System: Protects against overvoltage, overcurrent, overheating, short circuits, and leakage. For high-capacity battery packs in electric vehicles, this system is further upgraded with an HV safety system, cooling system, insulation monitoring, and automatic fire detection and suppression.
• Test Software: Sets up programs, controls equipment, and stores data.

6. Special significance for the electric vehicle industry

For electric vehicle batteries, cycle testing is crucial because the battery pack must operate stably for extended periods under heavy load. The test accurately simulates real-world vehicle scenarios: Charging → Driving → Energy Regeneration → Discharging → Recharging → Repeating, based on actual current and power profiles.

From the vast amount of data collected (voltage, current, power, capacity, temperature, SOC, SOH...), engineers can create intuitive graphs such as Capacity vs. Cycle Number to accurately predict battery behavior throughout its lifespan. This helps manufacturers easily compare materials, optimize charging/discharging algorithms, refine BMS system designs, and detect abnormal degradation early.

To meet the needs of comprehensive testing and evaluation of battery performance, durability, and lifespan, GPower Vietnam provides suitable battery charging and discharging system solutions  for various testing levels, from cells and modules to battery packs. These systems allow for precise control of the charging and discharging process, data collection, and the development of flexible test programs, effectively supporting R&D, quality control, and battery lifespan assessment.

For detailed information on Gpower Vietnam's products, please visit our website.

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