The standard pulse power density test uses controlled SOC points, short high-current pulses, and precise voltage measurement to determine a battery’s peak discharge and charge capability. A typical procedure fully charges the lithium-ion battery using CC-CV control, allows it to rest at a controlled temperature, then tests it at SOC levels from 90% down to 40%. At each level, the tester applies a 10-second discharge pulse, a charge pulse, and a controlled discharge step while recording current and terminal voltage at high sampling speed.
The test determines maximum pulse power and DC internal resistance under repeatable SOC and temperature conditions. The measured peak power must then be normalized by battery mass or volume to report power density, while voltage and current limits define the allowable operating range.
What the Test Measures
Peak Discharge and Charge Power
During each pulse, the battery’s instantaneous electrical power is calculated as:
[ P(t) = U(t) \times I(t) ]
where (U(t)) is the closed-circuit terminal voltage and (I(t)) is the pulse current.
The referenced procedure evaluates peak power using the voltage and current measured 0.1 seconds after the pulse begins. This early measurement captures a high-power operating condition while reducing the influence of slower thermal and electrochemical effects.
DC Internal Resistance
The pulse response also provides an estimate of DC internal resistance:
[ R_{\mathrm{DC}} = \frac{\Delta U}{\Delta I} ]
A larger voltage drop for a given current change indicates higher internal resistance and lower power capability.
The resistance value depends on the measurement interval. A resistance calculated immediately after the pulse begins will differ from one calculated after several seconds, so the test report must specify the timing convention.
Power Density
The measured peak power is converted into power density by dividing by the selected physical basis:
[ \rho_P = \frac{P_{\mathrm{max}}}{m} ]
for gravimetric power density in W/kg, or:
[ \rho_P = \frac{P_{\mathrm{max}}}{V_{\mathrm{battery}}} ]
for volumetric power density in W/L.
The report should state whether the calculation uses cell, module, or complete-pack mass and volume.
How to Prepare the Battery
Control the Test Environment
Conduct the test at a controlled ambient temperature, typically 20 ± 2 °C for the procedure described in the primary reference.
Temperature must be measured and recorded because lithium-ion resistance and power capability vary substantially with temperature. The battery should be thermally stabilized before testing begins.
Fully Charge the Battery
Begin with a complete constant-current/constant-voltage (CC-CV) charge using the manufacturer’s specified limits.
The charge should continue until the prescribed current-termination condition is reached. The applicable voltage, current, and termination values must come from the battery manufacturer or governing test standard.
Allow an Initial Rest
After charging, allow the battery to rest for one hour.
This rest period allows voltage relaxation and establishes a repeatable starting condition before the first pulse sequence.
How to Run the SOC Sequence
Select the Target SOC Levels
The primary procedure evaluates the battery at multiple SOC levels, progressing from approximately 90% SOC down to 40% SOC.
The exact SOC interval should be defined before testing. SOC must be calculated using a consistent method, normally based on calibrated coulomb counting with appropriate correction for the battery’s usable capacity.
Apply the Discharge Pulse
At each target SOC, apply a high-rate constant-current discharge pulse for 10 seconds.
The primary reference gives a representative discharge rate of 6C. The actual current should be selected according to the test specification, battery limits, and the capability of the test equipment.
Record:
- Pulse current
- Terminal voltage
- Time
- Battery temperature
- SOC
- Any protection or fault response
The pulse must stop if the battery reaches its specified minimum voltage, current, temperature, or safety limit.
Rest After Discharge
Allow the battery to rest for 40 seconds after the discharge pulse.
This interval provides a defined recovery period before the charging pulse and helps separate the immediate pulse response from subsequent relaxation behavior.
Apply the Charge Pulse
Apply a constant-current charge pulse for 10 seconds. The primary reference gives a representative charge rate of 3C.
The charging pulse must remain within the manufacturer’s maximum voltage, current, and temperature limits. Charging polarity should be documented clearly because some test standards use a sign convention in which discharge and charge currents have opposite signs.
Discharge at the Step Current
After the charge pulse, discharge the battery at 1C for 330 seconds.
This controlled discharge moves the battery toward the next SOC test point. The actual SOC change should be verified from the recorded current-time data rather than assumed solely from nominal C-rate calculations.
Rest Before the Next SOC Point
After the 330-second discharge, allow the battery to rest for one hour before beginning the next SOC step.
Repeat the pulse sequence until all specified SOC levels have been tested.
How to Determine Maximum Pulse Power
Use Voltage Limits as Constraints
A pulse current is only valid if the resulting terminal voltage remains within the permitted operating limits.
For discharge, the maximum allowable current is constrained by the minimum discharge voltage (U_{\min}). For charge, it is constrained by the maximum charge voltage (U_{\max}).
A simplified calculation is:
[ P_{\max}^{\mathrm{dis}} = U_{\min} \times I_{\max}^{\mathrm{dis}} ]
[ P_{\max}^{\mathrm{chr}} = U_{\max} \times I_{\max}^{\mathrm{chr}} ]
These values represent maximum allowable pulse discharge and charge power under the defined test conditions.
Use Incremental Pulse Currents When Required
Some procedures, including the JEVS D713-2003 approach described in the supplementary reference, apply a series of 10-second pulses at incrementally increasing C-rates.
A typical sequence may include zero-current rests and pulses at increasing charge and discharge magnitudes, such as 1C, 2C, and 3C. The terminal voltage measured at the end of each pulse is plotted against current to produce a voltage-current relationship.
The allowable current is then identified by extending or fitting that relationship to the specified voltage limits.
Measure at the Defined Time Point
For the primary procedure, calculate the reported peak power using the closed-circuit voltage and current 0.1 seconds after the pulse begins.
For a JEVS-style analysis, use the voltage at the end of the defined 10-second pulse. These are different measurement conventions and should not be mixed when comparing results.
Required Test Equipment and Data
Use a Programmable Battery Cycler
The test requires a programmable battery testing system capable of:
- CC-CV charging
- High-current pulse discharge
- High-current pulse charging
- Precisely timed rest periods
- SOC-based sequencing
- Fast voltage and current sampling
- Temperature monitoring
- Automatic safety-limit shutdown
The system must be rated for the battery’s maximum voltage, current, power, and stored energy.
Sample Quickly Enough
The initial voltage response occurs rapidly, so slow data logging can miss the relevant voltage drop.
The sampling rate, filtering, synchronization, sensor bandwidth, and measurement latency should be documented. Current and voltage channels must be time-aligned when calculating power or internal resistance.
Monitor the Complete Battery
For vehicle batteries, the test may involve a cell, module, or complete pack. At module and pack level, the procedure must also account for:
- Battery-management-system intervention
- Contactor behavior
- Cell imbalance
- Cooling-system operation
- Pack current limits
- Isolation monitoring
- Overvoltage and undervoltage protection
A pack-level result is not necessarily predictable from a single-cell result because the weakest cell or module can determine the usable pulse limit.
Understanding the Trade-offs
Peak Power Is Not Continuous Power
A 10-second pulse rating describes short-duration performance. It does not establish the power the battery can deliver continuously without overheating or exceeding thermal limits.
Continuous-power capability requires a separate test with appropriate thermal stabilization and duration.
Higher C-Rates Increase Stress
High-rate pulses produce greater voltage sag, heat generation, and electrochemical stress.
Repeated testing can alter battery condition, especially when the battery is exposed to high charge rates or operates near voltage and temperature limits. Test order, cycle count, and preconditioning therefore need to be recorded.
SOC Alone Does Not Define Performance
The same SOC can produce different results depending on temperature, aging, prior current history, rest time, and capacity measurement method.
Comparisons are meaningful only when these conditions are controlled or explicitly reported.
Power Density Depends on the Measurement Boundary
A cell-level W/kg value should not be compared directly with a pack-level W/kg value unless the mass boundary is identical.
The report should identify whether inactive packaging, cooling hardware, busbars, electronics, and enclosure mass are included.
Standards Use Different Conventions
The primary procedure uses a defined discharge-charge-discharge sequence and evaluates power at a specified early pulse time. JEVS-style testing may use multiple incremental pulses and the voltage measured at the end of each 10-second pulse.
These methods can produce different power and resistance values, so the governing standard and calculation timing must always be stated.
Making the Right Choice for Your Goal
Use the test method that matches the performance claim you need to support.
- If your primary focus is vehicle acceleration or regenerative braking: Test both discharge and charge pulses at relevant SOC and temperature conditions, using the vehicle battery’s actual voltage and current limits.
- If your primary focus is comparing cells or modules: Keep temperature, SOC definition, pulse timing, rest periods, and mass boundaries identical across all samples.
- If your primary focus is DC internal resistance: Record synchronized voltage and current at a clearly specified time point and report the calculation interval.
- If your primary focus is a formal standard comparison: Follow one complete standard procedure without combining its timing, pulse sequence, or voltage-limit rules with another method.
- If your primary focus is power density: Report peak power together with the exact mass or volume basis used for normalization.
A reliable pulse power density result is defined as much by its test conditions and calculation conventions as by the battery’s raw peak power.
Summary Table:
| Step | Description | Key Parameters |
|---|---|---|
| 1. Environment | Control temperature at 20 ± 2°C | Temperature, stabilization time |
| 2. Charging | Full CC-CV charge | Voltage, current, termination condition |
| 3. Rest | Allow 1-hour rest | Rest time |
| 4. SOC sequence | Test at SOC levels from 90% down to 40% | SOC points, intervals |
| 5. Discharge pulse | 10s at 6C (representative) | Current, voltage, time, temperature |
| 6. Rest | 40s after discharge | Rest time |
| 7. Charge pulse | 10s at 3C (representative) | Current, voltage, time, temperature |
| 8. Discharge step | 1C for 330 seconds | Current, time |
| 9. Rest | 1-hour rest before next SOC | Rest time |
| 10. Data analysis | Calculate peak power and resistance at 0.1s | Voltage, current, time, resistance |
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