In the research, development, quality verification, and application of lithium-ion batteries, accurate, reliable, and efficient testing is the foundation for obtaining authentic battery performance data. Whether evaluating the intrinsic properties of battery materials or verifying the durability and safety of battery packs under complex operating conditions, standardized and systematic testing is indispensable.
The test step is the core operation in battery testing, which essentially involves precise control of parameters such as current, voltage, power, or resistance. This article systematically introduces common charge/discharge steps and auxiliary/control steps in battery testing systems. Using BTS 8.0 software as an example, it elaborates on the working principles, key parameter settings, data recording strategies, and typical application scenarios of various charge/discharge steps as well as auxiliary and control steps.
1. Constant Current Charge
Abbreviation in BTS 8.0 software: CC Chg
Description: Charges the battery at a set constant current until voltage, time, or other cut-off conditions are met.
Key parameter settings:
Current: Set to a positive value, e.g., 1A, 0.5C (when using rate mode, the current value is automatically calculated).
Cut-off conditions: Charge cut-off voltage (typically between 3.6V and 4.5V, depending on the battery's cathode material) to prevent overcharging. Capacity or time cut-offs can also be set as secondary or safety conditions.
Data recording: Typically recorded at time intervals (e.g., 1-10 seconds) or voltage change intervals (e.g., ΔV = 0.001-0.005V). For high-current fast charging, shorter time intervals are recommended to capture voltage change details.
Application scenarios: Capacity testing, rate performance testing, and the charging phase of cycle tests (often combined with CV as CCCV).
2. Constant Voltage Charge
Abbreviation in BTS 8.0 software: CV Chg
Description: Used at the end of the charging process. Maintains the battery voltage at a constant value, while the charging current decays exponentially as the battery's saturation level increases.
Key parameter settings:
Voltage: Set to the charge cut-off voltage, e.g., 4.2V.
Cut-off conditions: Current cut-off is typically set to a very small value (e.g., 0.05C), indicating that the battery is fully charged when the current decays to this value. A time cut-off is also set to prevent failure to reach the current cut-off.
Data recording: Initially recorded at time intervals (e.g., 10-30 seconds), with intervals increased later as current changes slow. It is highly recommended to use current change intervals (e.g., ΔI = 0.01C) or capacity change intervals (e.g., ΔCap = 0.1mAh) to accurately record the current decay curve for calculating saturation levels.
Application scenarios: Battery discharge performance testing or combined with constant current charge (CC) to form the CC-CV charging mode.
3. Constant Power Charge
Abbreviation in BTS 8.0 software: CP Chg
Description: Charges the battery at a set constant power. The system maintains constant power by calculating voltage and current in real time.
Key parameter settings:
Power: Set the charging power value, e.g., 3W.
Cut-off conditions: Typically voltage cut-off and time cut-off are set.
Data recording: Since power is constant, voltage and current change simultaneously. Real-time power, voltage, and current curves must be recorded.
Application scenarios: Simulating specific charger characteristics; fast-charging research.
4. Constant Current and Constant Voltage Charge
Abbreviation in BTS 8.0 software: CCCV Chg
Description: A combined mode of CC Chg and CV Chg, completing both stages in one step.
Key parameter settings:
Current: Current for the constant current phase (e.g., 1C).
Voltage: Voltage for the constant voltage phase (e.g., 4.2V), which is also the cut-off voltage for the constant current phase.
Cut-off conditions: Current cut-off (for the CV phase) and time cut-off.
Application scenarios: Standard charging step for lithium-ion batteries.
5. Pack Constant Current Constant Voltage
Abbreviation in BTS 8.0 software: PCCCV Chg
Description: A CCCV charging mode specifically designed for battery packs (Packs) composed of multiple cells in series.
Key parameter settings:
Current: Charging current.
Voltage: Calculated based on the single-cell cut-off voltage multiplied by the number of series cells.
Cut-off conditions: Current cut-off and time cut-off.
Data recording: Same as for single-cell CCCV.
Application scenarios: Direct testing of finished battery packs.
6. Constant Current Discharge
Abbreviation in BTS 8.0 software: CC DChg
Description: Discharges the battery at a set constant current until the specified cut-off conditions are met.
Key parameter settings:
Current: Discharge current.
Cut-off conditions: Cut-off voltage, capacity cut-off, or time cut-off.
Data recording: For capacity tests, record discharge capacity at time intervals. To plot high-resolution discharge curves, record real-time voltage at voltage change intervals (e.g., ΔV = 0.001V).
Application scenarios: Battery discharge performance testing, used to measure capacity, energy efficiency, cycle life, etc.
7. Constant Voltage Discharge
Abbreviation in BTS 8.0 software: CV DChg
Description: Maintains the battery voltage at a constant value during discharge, with the current determined by the load.
Key parameter settings:
Voltage: Set a low voltage value, e.g., 3.0V.
Cut-off conditions: Typically current cut-off or time cut-off.
Data recording: Record at time intervals or current change intervals to observe current decay behavior.
Application scenarios: Simulating regulated power supply output; testing battery load response under constant voltage.
8. Constant Power Discharge
Abbreviation in BTS 8.0 software: CP DChg
Description: Discharges the battery at a set constant power.
Key parameter settings:
Power: Discharge power value.
Cut-off conditions: Voltage cut-off and time cut-off.
Data recording: Record at time intervals. Dense recording is required to analyze the dynamic relationship between voltage and current under constant power.
Application scenarios: Simulating real-world device operation; testing battery peak power output performance.
9. Constant Current and Constant Voltage Discharge
Abbreviation in BTS 8.0 software: CCCV DChg
Description: Discharges first at constant current, then switches to constant voltage discharge after reaching the cut-off voltage.
Key parameter settings: Similar to CCCV charging, but the current is set to a negative value, and the voltage is the discharge cut-off voltage.
Data recording: Use a hybrid strategy similar to CCCV charging: record at voltage intervals during the CC phase and at current intervals during the CV phase.
Application scenarios: Tests requiring complete battery discharge.
10. Constant Resistance Discharge
Abbreviation in BTS 8.0 software: CR DChg
Description: Simulates a constant resistance load connected to the battery for discharge.
Key parameter settings:
Resistance: Set the load resistance value.
Cut-off conditions: Voltage cut-off and time cut-off.
Data recording: Record at time intervals (e.g., 5 seconds) to plot the natural decay curve of voltage and current over time.
Application scenarios: Simulating simple resistive loads.
11. Rest
Abbreviation in BTS 8.0 software: Rest
Description: No current is applied to the battery, leaving it in an open-circuit state. The purpose is to allow relaxation and stabilization of internal ion concentration gradients and polarization voltages.
Key parameter settings:
Time: Set the duration of rest, e.g., 300s or 1h.
Application scenarios: An essential step between charge/discharge steps. Used to record open-circuit voltage (OCV), measure battery self-discharge, and allow battery reactions to stabilize before proceeding to the next step.
12. Cycle
Abbreviation in BTS 8.0 software: Cycle
Description: Defines a series of steps (e.g., CCCV Charge → Rest → CC Discharge → Rest) as a cycle body and sets the number of repetitions.
Key parameter settings:
Cycle Count: Set the number of repetitions required, e.g., 1000 times.
13. Pulse
Abbreviation in BTS 8.0 software: Pulse
Description: Applies a high-intensity charge or discharge current for a very short duration, followed by rest or recovery. Used to test the battery's instantaneous power capability and internal resistance.
Key parameter settings: Current, pulse duration, rest time.
Application scenarios: Hybrid Pulse Power Characterization (HPPC) for calculating internal resistance and power window; simulating pulse conditions such as start-stop and acceleration.
14. Ramp
Abbreviation in BTS 8.0 software: Ramp
Description: Changes voltage or current at a constant slope rather than in step changes.
Key parameter settings: Start/peak/end voltage, scan rate (e.g., mV/s).
Application scenarios: Used for studying battery reaction mechanisms, redox potentials, reversibility, etc., belonging to fundamental research at the material level.
15. Cyclic Voltammetry
Abbreviation in BTS 8.0 software: Cyclic Voltamm
Description: An important electrochemical analysis technique. The voltage of the working electrode (battery) is scanned at a constant rate, and the response current is measured.
Key parameter settings: Start/peak/end voltage, scan rate (e.g., mV/s), cycle count.
Application scenarios: Used for studying battery reaction mechanisms, redox potentials, reversibility, etc., belonging to fundamental research at the material level.
16. Simulation
Abbreviation in BTS 8.0 software: SIM
Description: Imports a data file composed of time-current or time-power profiles, enabling the test system to accurately reproduce complex charge/discharge waveforms.
Application scenarios: Simulating real-world application scenarios, such as UDDS and WLTC cycles for electric vehicles or daily usage patterns for mobile phones. This is the most direct method for validating battery performance in practical applications.
17. Control
Abbreviation in BTS 8.0 software: Control
Description: Used to issue commands controlling other channels or devices, without performing charge/discharge operations on the current channel's battery.
Key parameter settings:
Control commands (e.g., start/stop other channels, trigger external devices).
Application scenarios: Multi-channel coordinated testing, e.g., triggering another channel to start testing when a specific condition is met in one channel's step.
18. Follow Step
Abbreviation in BTS 8.0 software: Follow Step
Description: Enables one channel's test parameters (e.g., current) to follow another channel's values in real time.
Key parameter settings: Channel number to follow, scaling factor.
Application scenarios: Used for battery pack testing, where the master channel controls the entire pack and slave channels follow the master channel's current to simulate individual cell behavior within the pack; also used for comparative testing.
19. Pause
Abbreviation in BTS 8.0 software: Pause
Description: Automatically pauses program execution at this point, waiting for user confirmation before continuing. Usually accompanied by a prompt message.
Key parameter settings: Pause trigger conditions (e.g., pause after every 5 cycles).
Application scenarios: Used when manual intervention is required during testing, e.g., changing the test environment (placing the battery in a thermal chamber before resuming testing) or connecting additional measurement equipment.
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