3.2 benchmark energy content the battery energy content measured during the reference test cycle and used as the reference value to assess the battery deterioration during its life 3.3
Accuracy of measuring instruments
Electrical measuring instruments
The instruments employed must accurately measure voltage and current, with their range and methods selected to meet the specified accuracy for each test For analog instruments, readings should be taken within the last third of the graduated scale to ensure precision.
Any other measuring instruments may be used provided they give an equivalent accuracy
For accurate voltage measurement, voltmeters with an accuracy class of 0.5 or better should be utilized Additionally, these voltmeters must have a resistance of at least 1,000 Ω/V, in accordance with the IEC 60051 series standards.
For accurate current measurement, ammeters must have an accuracy class of 0.5 or better Additionally, the complete setup, including the ammeter, shunt, and leads, should also meet the same accuracy standard of 0.5 or better, as specified in the IEC 60051 series and IEC 60359.
Temperature measurement
Temperature measuring instruments must possess an appropriate range, ensuring that no graduated division exceeds 1 K Additionally, the instruments should maintain an absolute accuracy of at least 0.5 K.
The temperature measuring point should be determined by the manufacturer to accurately reflect the electrolyte temperature If no specific location is provided, it should be positioned at the center of the longer side of the cell, whether it is a single cell or part of a monobloc assembly.
For battery systems equipped with a thermal management system or when cells are not directly accessible for temperature measurement, the battery management system (BMS) provided by the manufacturer can be utilized to measure temperature effectively.
Electrolyte density measurement of vented lead-acid batteries
To measure electrolyte densities, hydrometers must be utilized with scales that have divisions not exceeding 5 kg/m³ Additionally, the instrument's absolute accuracy should be a minimum of 5 kg/m³.
Tolerance
The accuracy of controlled or measured values must adhere to specific tolerances: ± 1% for voltage and current, ± 2% for power, ± 2 K for temperature, and ± 0.1% for time, dimensions, and mass.
These tolerances comprise the combined accuracy of the measuring instruments, the measurement technique used, and all other sources of error in the test procedure.
General provisions
Current slew rate
The current slew rate, defined as the time interval in seconds between two steady currents, must be ≤ 1 second during dynamic tests.
Switching between power levels in the micro-cycle shall be timed such that the mid-point of the transition occurs at the point allocated for the transition
The total duration of each complete micro-cycle shall be 360 s ± 1 s.
Temperature – electrolyte accessible
The cell temperature shall be measured by use of a temperature probe immersed in the electrolyte above the plates
Temperature – electrolyte not accessible
The cell temperature shall be measured by use of a surface temperature-measuring device The temperature shall be measured at a location, which most closely reflects the electrolyte temperature.
Electrolyte density readings of vented lead-acid batteries
Electrolyte density readings should be conducted at optimal times for the test sample, considering the different stabilization rates of cells and adhering to the limitations of the testing system.
Mechanical support
If necessary, mechanical support should be provided for the test samples in order to maintain the same dimensions as when installed in batteries, as specified by manufacturer.
Test samples
Cells in the test unit must demonstrate an actual capacity that meets or exceeds the rated capacity before undergoing dynamic discharge performance or endurance testing.
A minimum of five cells must be tested under each test condition, while for monoblocs, at least two test samples are required.
Applications tests for batteries tailored to specific vehicles may utilize either a complete battery or a representative section, as mutually agreed upon by battery and vehicle manufacturers.
Test temperature
Test temperature for type testing
4.4.1.1 For Lead-acid batteries, the battery temperature at the start of the discharge should be the specified test temperature ± 5K
When the initial cell temperature at the start of discharge differs from the reference temperature and significantly impacts the outcome, a suitable correction factor must be applied to the resulting capacity.
The following formula can be used to correct capacity values to the actual capacity
C a is the actual capacity of the test sample at the reference temperature;
C is the measured capacity at the initial temperature; t 0 is the initial temperature; λ is the temperature correction factor (see Table 1 for values)
Following discharge, the cells/battery shall be fully charged in accordance with the manufacturer’s recommendations and then stabilized to the specified test temperature during a
1 h – 4 h period prior to the next discharge
4.4.1.2 For Ni/MH and Ni/Cd batteries, the battery temperature at the start of the discharge should be the specified test temperature ± 2 K For sodium based batteries, the internal temperature measured by BMS should be in the range recommended by the battery manufacturer
Operation of BMS
A battery system provided with a BMS shall have this function operational during the test All systems shall be powered as specified by the battery manufacturer.
Charging and rest after charge
Cells must be charged according to the manufacturer's specified procedure and within the limits set by this standard before conducting the discharge test Following the charging process, the test sample should be stored for a duration of 1 to 4 hours at the declared test ambient temperature.
Conditioning
Before conducting the test, it is essential to condition the battery in accordance with the manufacturer's specifications Conditioning should cease once the rated capacity is reached, and the total number of conditioning cycles must not exceed 20.
Test sequence
The following tests shall be carried out in the order stated in this standard:
– dynamic discharge performance test (see Clause 6),
– dynamic endurance test (see Clause 7).
Data recording
General
Data recording shall include time, temperature, voltage and current and visual observations Data shall include a record of any maintenance performed on battery samples during the test sequence.
Sampling frequency
To ensure accurate data analysis, all parameters must be measured and stored at a sufficient sample rate to capture relevant deviations For tests involving short-term transient conditions, such as peak power measurement, it is crucial to maintain an appropriate sampling frequency, typically once per second, and to minimize the time difference between corresponding current and voltage measurements, ideally to 0.1 seconds or less, during the critical test period.
General
This test measures the ampere-hour (Ah) capacity of batteries, cells, or modules when discharged at a constant current The rated capacity is defined as the 3-hour capacity at a temperature of 25 °C, as declared by the manufacturer, unless specified otherwise.
The battery shall be discharged at a constant current of: h 3
I to a final voltage of U f3 where
I n is the constant current in amperes (A);
C n is the rated capacity as declared by the manufacturer, in ampere-hours (Ah);
U f3 is the final voltage specified for the battery type in volts (V) (see Table 1)
New batteries undergoing capacity testing are permitted a maximum of 20 cycles to reach their rated capacity, with testing ceasing once this capacity is achieved Batteries failing to meet the rated capacity by the 20th cycle are deemed unsuitable for testing For road vehicle applications, additional capacities of 5 h, 1 h, and 0.5 h are also considered appropriate, along with the relevant final voltages for C5.
C 1 and C 0,5 capacities, i.e U 5 , U 1 and U 0,5 are contained in Table 1
NOTE The capacity test for Ni/MH batteries used for the propulsion of HEV is specified in Annex A.
Additional test temperatures
Where appropriate to the battery type, the following cell/battery test temperatures could provide a useful profile of performance: 45 °C, 0 °C and –20 °C
Basic considerations
The aim of this test is to determine the conditions necessary to calculate the battery capacity, which is directly linked to the available capacity in electric road vehicle applications.
In electric vehicle applications, propulsion batteries must deliver a range of current rates to accommodate different driving conditions These conditions include high-rate current for acceleration, low-rate current for steady-speed driving, and zero current during rest periods Additionally, the test profile incorporates a high-rate recharge pulse to account for battery recharging during vehicle braking through regenerative charging.
Test temperatures are specified in Table 1.
Test cycle definition without regenerative charging
The dynamic discharge performance cycle shall be represented by a 60 s repeated micro-cycle having three current levels:
Test cycle definition with regenerative charging
The dynamic discharge performance cycle shall be represented by a 60 s repeated micro-cycle having four current levels:
The manufacturer can prescribe a maximum voltage that shall not be exceeded during the I rc pulse
Definition of dynamic discharge performance
Test cycle without regenerative charging
The dynamic capacity C da, expressed in ampere-hours (Ah), represents the total discharge of cells during a repeated cycle, as outlined in section 6.2 This process begins with a battery that has been charged and stored according to the guidelines in section 4.5, ultimately reaching a final discharge voltage of U f (V) per cell.
Test cycle with regenerative charging
The dynamic capacity \( C_{dar} \) (measured in ampere-hours, Ah) represents the net discharge amount, calculated by subtracting the regenerative charge capacity from the total discharged capacity This measurement is taken when cells are discharged according to the specified cycle, beginning with a battery that has been charged and stored as outlined, and concluding at a final discharge voltage of \( U_f \) (V) per cell.
Basic considerations
The purpose of this test is to assess the total number of discharge cycles until the actual capacity (C da or C dar) decreases to 80% of its initial value, following the procedures outlined in sections 6.2 or 6.3.
Test conditions
The dynamic endurance test should be conducted with the test unit partially submerged in an oil or water bath, maintaining a temperature within ± 2 K of the specified value Efficient cooling of the cells is ensured through proper circulation within the bath, with test temperatures outlined in Table 1.
In situations where physical limitations restrict the use of liquid coolants, air-cooling becomes a viable alternative For batteries equipped with an integrated thermal management system, it is essential to apply the same testing conditions as those used in liquid thermal management.
During the test, if applicable and necessary, the electrolyte level shall be kept within the limits recommended by the manufacturer.
Test cycle without regenerative charging
The dynamic endurance cycle shall be represented by a 60 s repeated micro-cycle as defined in 6.2 (see Figure 1 and Table 2)
The discharge cycle duration shall be fixed to 80 % of the value obtained when the battery was tested according to 6.2, and assessed according to 6.4.1, prior to the endurance test.
Test cycle with regenerative charging
The dynamic endurance cycle shall be represented by a 60 s repeated micro-cycle as defined in 6.3 (see Figure 2 and Table 2)
The discharge cycle duration shall be fixed to 80 % of the value obtained when the battery was tested according to 6.3, and assessed according to 6.4.2, prior to the endurance test.
Endurance test
Charge conditions
The recharge shall follow within 1 h after the previous discharge The charge profile, as stated by the manufacturer, preferably should allow for a full recharge within 8 h
Rest after charge
After the recharge, the battery shall be stored for 1 h to 4 h.
Discharge
The discharge shall be carried out using the test cycle described in 7.3 or 7.4.
Cycling frequency
When possible, the charge and rest periods shall be arranged to allow at least two charge/discharge cycles per day.
Capacity check
At regular intervals of 50 cycles, a dynamic discharge performance test shall be performed according to 6.2 or 6.3 to record the capacity development.
Reconditioning
A reconditioning cycle specified by the manufacturer is allowed at intervals of not less than
End-of-life criterion
The end of a battery's life is defined as the point when its capacity drops to 80% of the original capacity measured during testing as per sections 6.2 or 6.3, or when it falls below this threshold on two consecutive cycles.
The endurance test is then considered as completed.
Recording
The following shall be recorded:
– calculated capacity for each discharge cycle;
– total number of discharge cycles achieved
8 Performance testing for battery systems
General
The test procedures of this clause are applicable to battery systems used in battery electric vehicles
There are three fundamental tests i.e., tests for energy (range), power (performance), and life All other tests are optional.
Initial assumptions
To ensure that vehicle tests accurately reflect real-world operation, the discharge rate and battery size must align with those used in urban settings Currently, the primary constraint in battery selection is the weight that the vehicle can support As technology advances, the focus will shift to the range or driving time for town vehicles Consequently, battery selection criteria prioritize weight first, followed by range, provided the battery's capacity within that weight meets the necessary range Typical figures representative of urban operation are outlined for reference.
Energy consumption, from the battery: 100 Wh/tonne × km
In addition, the basic tests shall be performed at an ambient temperature of 25 °C
The average power drain from a vehicle's battery is 3 kW per tonne of weight, which means a 15 kWh battery can power a one-tonne vehicle for 150 km in urban conditions.
The selection of battery weight, volume, and capacity for a vehicle is influenced by various factors, including the vehicle's design and available space for the battery system The following figures are suggested as a guideline for battery selection.
• maximum battery weight fraction in the fully laden vehicle: 30 %;
• maximum range required for an urban vehicle: 150 km.
General test conditions
General
The battery system must be fully charged at an ambient temperature of 25 °C, following the manufacturer's guidelines Testing should occur at this temperature and under typical airflow conditions similar to those in a vehicle Airflow must be maintained during discharge but not during charging If necessary, battery heating or cooling powered by the battery system should be operational Additionally, any energy consumed from an external power source used to power the Battery Management System (BMS) must be recorded and reported.
The operating voltage range for each micro-cycle during the battery capacity tests in the life test program must be documented, including both the minimum voltage during discharge and the maximum voltage during charge.
Most traction batteries available today cannot withstand continuous extreme operating conditions without sustaining damage To safeguard against this, the Battery Management System (BMS) plays a crucial role The upcoming tests aim to determine the operational limits set by the BMS in scenarios that the battery system cannot tolerate This underscores the necessity for precise and dependable communication between the BMS and the vehicle system, as even a few minutes of extreme operation can lead to irreversible damage to the battery.
Using an average airflow over the battery is acceptable instead of adjusting the flow based on the calculated vehicle speed It is advisable to maintain a constant airflow rate that aligns with an average vehicle speed of 30 km/h during testing.
Determination of battery energy content
The battery energy content is determined using the reference test cycle outlined in section 8.3 Continuous testing of the battery system involves repeating the basic current discharge micro-cycle at specified power levels, with the test concluding when the battery can no longer provide the required power or when the Battery Management System (BMS) terminates the discharge The reason for test termination must be documented in the test records Throughout the test, a continuous record of the battery system voltage is maintained Key data, including the test cycle values, total number of micro-cycles, total watt-hours (Wh) discharged, and total Wh returned during simulated regenerative braking, must be recorded The net battery energy content is reported as the difference between the total Wh removed and the total Wh returned.
The BMS may terminate on the basis of ampere-hours, temperature, voltage or for any other reason associated with battery longevity or safety.
Benchmark energy content
After the initial conditioning of a new battery system, the reference test cycle must be conducted 10 times, with one cycle per day, to ensure consistent capacity measurements The net energy extracted during each of the 10 tests will be documented, and the net energy from the final test will be declared as the benchmark energy content.
Life testing
The reference test cycle is essential for assessing battery life, involving a discharge until 80% of the benchmark energy content is depleted or until the end of the micro-cycle Following this, the battery must be recharged within one hour of discharge completion, and the subsequent discharge should commence within one hour after the recharge is finished.
The start of discharge may be delayed in order to fit in with the normal working practices of the test laboratory
Every 50 cycles, the battery's energy content is assessed using a benchmark test cycle, which establishes its actual energy capacity and facilitates the measurement of additional parameters During this evaluation, continuous monitoring of the battery system voltage is conducted to determine other system metrics Furthermore, the total number of micro-cycles, along with the total watt-hours (Wh) removed and returned, are recorded and reported as the battery's energy content at this phase of the life test program.
It is permissible for the battery manufacturer to utilise a conditioning procedure immediately after the completion of the full benchmark energy content test, if required
The life test will conclude when the energy output drops below 80% of the reference energy content The total number of reference test cycles will be documented and reported as the battery's lifespan.
The intervals between the battery energy content tests may be modified to give approximately
10 of these tests during the anticipated lifetime of the battery.
Determination of maximum power and battery resistance
Maximum deliverable power is defined as the power level at which the current drawn reduces the battery terminal voltage to two-thirds of its open circuit value To determine this maximum power and battery resistance, voltage and current measurements must be taken during the battery energy content test, specifically at the end of steps 14 and 15 in Tables 3 and 4 The discharge resistance and open circuit voltage are calculated using the differences in current and voltage at these points, with the assumption that discharge resistance is linear between zero current and maximum power.
The battery resistance is given by:
The open circuit voltage is given by:
The current required to depress the voltage to 2/3 V oc is given by : batt pk 3R oc
I = V and the maximum power by :
R batt is the calculated battery resistance;
V oc is the calculated open circuit voltage of the battery;
I pk is the calculated peak current at maximum power;
P max is the calculated maximum power of the battery
The calculated battery resistance, the calculated open circuit voltage and the calculated maximum battery power shall be declared in the results
Important battery parameters are defined based on vehicle requirements Experimentally determining the true maximum power can stress specific battery components and is generally unnecessary.
Charging tests
Charge efficiency
8.7.1.1 Charge efficiency during normal operation
Charge efficiency is determined by measuring the energy input and output during each discharge and charge cycle of the battery life testing program This calculation must account for losses related to the Battery Management System (BMS), if applicable, as well as any losses from maintenance or equalizing charges throughout the testing period.
Battery efficiency is determined by comparing the energy input to the battery with the energy output during each capacity test conducted throughout the life testing program.
The charge efficiency may be determined for discharge to other states of charge (e.g 80 % depth of discharge (DOD)), though separate tests will be required to establish these results
If required, the efficiency of the charger may also be measured during this test, though the procedure for doing this is outside the scope of this standard
The battery system must be discharged to 40% state of charge (SOC), removing 60% of the benchmark energy content, and then rapidly recharged to 80% SOC as per the manufacturer's guidelines The energy content will be measured using a reference test cycle to ensure complete discharge, and the effectiveness of the rapid charging process in replenishing energy will be evaluated Additionally, the rapid charging method, the watt-hours returned to the battery, and the overall energy content will be documented.
Tests can assess the rapid charge acceptance of battery systems by evaluating their sub-systems These sub-systems should be prepared similarly to the complete battery system, ensuring that the benchmark energy content is verified.
Partial discharge testing
The battery system will be discharged to 80% state of charge (SOC), representing 20% of the benchmark capacity, and then recharged normally This process will be repeated daily for a total of 20 cycles Following this, the battery will undergo the capacity test outlined in section 8.4.3, with the capacity recorded and declared Additionally, the capacity test may be conducted up to five times to evaluate any potential capacity recovery effects.
In this case, the measured capacity after each test shall be recorded and declared
This test may be repeated using 50 % SOC as the depth of discharge, if required
Battery systems that undergo continuous partial discharge testing may need regular conditioning cycles It is essential to document the use of these conditioning cycles and record the relevant details.
Tests to determine the effects of partial discharge testing may be made on sub-systems of the complete battery system.
Measurement of self discharge
The battery system must be fully charged and left disconnected from any external supply for 30 days at a reference temperature of 25 °C After this period, the energy will be measured as per section 8.4.2, and the results will be documented The energy loss recorded will be attributed to self-discharge during the standing period.
To assess the permanent self-discharge loss, fully charge the battery system and then perform the discharge test again at the ambient reference temperature as outlined in section 8.4.2 The energy loss will then be reported.
An external device may be necessary to maintain the battery in its operational state In this case, the power consumption should be included in the calculation of self discharge
The self-discharge test can be conducted for various stand durations and ambient temperatures, with preferred durations of two and five days, and preferred temperatures of −20 °C and +40 °C Before performing the test at these alternative temperatures, it is essential to determine the battery's capacity by conducting the tests outlined in sections 8.4.2 and 8.4.3 at the specified ambient conditions.
To evaluate the self-discharge characteristics of a battery system, tests can be conducted on a sub-system of the complete battery system During these tests, any parasitic loads on the battery must be simulated and scaled to accurately reflect those relevant to the full-sized battery system.
Operational extremes of use
Continuous discharge at maximum vehicle system power
Operating a vehicle continuously at high power is feasible under various conditions, such as extended hill climbing or prolonged towing of another vehicle.
The battery must be fully charged and then discharged at the vehicle system's maximum power level as defined in the reference test cycle Continuous recording of current and voltage is required throughout the test, which concludes once any manufacturer-imposed limits are reached Additionally, the test will document the duration for which maximum power can be maintained and the power/time curve permitted by the Battery Management System (BMS) if discharge continues at a reduced power level.
Recharge at maximum regenerative power as a function of state of
In urban driving, vehicles typically cannot maintain high levels of regenerative power; however, this changes when towing or commuting to out-of-town areas The most challenging scenario occurs when the battery must accept maximum regenerative power while fully charged A Battery Management System (BMS) can mitigate this by instructing the vehicle's drive system to lower regenerative power It is essential to inform the vehicle manufacturer about the interfacing requirements prior to conducting such tests.
The reference test cycle shall be used to discharge the battery to the specific depth of discharge,
The battery management system (BMS) allows for minimum values of 0% and maximum values of 25%, 50%, or 75% During testing, the battery system will undergo maximum regenerative braking power as defined in the reference test cycle for a duration of 15 minutes, with continuous monitoring of current, voltage, and temperature The test will conclude once the vehicle system limits or any restrictions set by the battery manufacturer are met.
The test will measure the duration of maximum regenerative power sustainability and the power time curve permitted by the Battery Management System (BMS), provided that recharging continues at a reduced power level.
Dynamic discharge profile without regenerative charging
Figure 1 – Test profile without regenerative charging
Dynamic discharge profile with regenerative charging
Figure 2 – Test profile with regenerative charging
Table 1 – List of parameters for test conditions
Parameter Lead-acid Ni/Cd Ni/MH Sodium based a
Test ambient reference temperature T (°C) 25 25 25 25 λ – temperature correction 5 h 0,006 0 0 0 λ – temperature correction 3 h 0,006 5 0 0 0 λ – temperature correction 1 h 0,007 0 0 0 λ – temperature correction 0,5 h 0,01 b 0 0 0 a Voltage values to be used in the test can be stated by the manufacturer b See IEC 60254-1
Table 2 – List of charge/discharge parameters
Parameter Lead-acid Ni/Cd Ni/MH Sodium based a
High-current discharge pulse I dh (A) 5,2 × I 3 5,2 × I 3 5,2 × I 3 5,2 × I 3 Low-current discharge pulse I dl (A) 1,3 × I 3 1,3 × I 3 1,3 × I 3 1,3 × I 3 Regenerative charge pulse I rc (A) 2,6 × I 3 2,6 × I 3 2,6 × I 3 2,6 × I 3 a Voltage values to be used in the test can be stated by the manufacturer
Table 3 – List of DST values for one micro-cycle, where the peak power is 24 kW
The regenerative power values are determined based on the DST power profile requirements To avoid significant overcharging, the Battery Management System (BMS) may restrict the actual power supplied to the battery in certain situations.
Table 4 – List of DST values for one micro-cycle, adapted for a high performance vehicle
No Duration s Power kW Step
Test procedures for Ni-MH batteries used for the propulsion of hybrid electric vehicles
This annex describes performance and cycle life test procedures of Ni-MH batteries (cells) used for the propulsion of hybrid electric vehicles
In this annex, sealed nickel-metal hydride (Ni-MH) batteries are defined as batteries that utilize nickel hydroxide at the positive electrode and a hydrogen-storing alloy at the negative electrode, with an alkali aqueous solution like potassium hydrate serving as the electrolyte These sealed batteries are designed to maintain their integrity without releasing gas or liquid during charging and discharging within the manufacturer's specified temperature range Additionally, they feature a gas discharge mechanism to safely manage internal pressure buildup.
If not otherwise defined before each test, cell or battery has to be stabilised at the test temperature for a period specified in Table A.1
Table A.1 – Battery temperature and rest period prior to the test
Battery temperature at test commencement °C
Rest period prior to starting the test h
Cell temperature must be measured using a surface temperature measuring device that meets the calibration and scale accuracy requirements outlined in section 4.1.1.1 It is essential to take the measurement at a location that best represents the actual cell temperature, with the option to measure at additional suitable locations if needed.
The examples for temperature measurement are shown in Figure A.1 The instructions for temperature measurement specified by the manufacturer shall be followed
Figure A.1 – Example of temperature measurement of cell
The maximum dimension of the total width, thickness or diameter, and length of a cell shall be measured up to three significant figures in accordance with the tolerances in 4.1.4
The examples of maximum dimension are shown in Figures A.2a) to A.2d)
Figure A.2a) – Cylindrical cell (a) Figure A.2b) – Cylindrical cell (b)
Figure A.2c) – Prismatic cell (a) Figure A.2d) – Prismatic cell (b)
D is total length (including terminals);
E is total length (excluding terminals)
Figure A.2 – Examples of maximum dimension of cell
During each test, voltage, current and temperature shall be recorded
Unless otherwise stated in this standard, prior to electrical measurement test, the cell shall be charged as follows
Before charging, the cell must be discharged at a temperature of 25 °C ± 2 K using a constant current of 1/3 I t (A) until it reaches the end-of-discharge voltage specified by the manufacturer Following this, the cell should be charged according to the manufacturer's declared charging method, also at 25 °C ± 2 K.
Capacity of cell shall be measured in accordance with the following steps
Step 1 – The cell shall be charged in accordance with A.3.2
After recharge, the cell temperature shall be stabilized in accordance with A.2
Step 2 – The cell shall be discharged at a constant current as specified in Table A.2 and Table A.3 at –20 °C, 0 °C, 25 °C and 45 °C to the end-of-discharge voltage as specified in Table A.4 The upper limit of the discharge current shall be 200 A The end-of-discharge voltage is expressed as the product of the end-of-discharge voltage of a cell and the number of cells
Table A.2 – Discharge current at the battery temperature 25 °C
Rated capacity classification of battery
Table A.3 – Discharge current at the battery temperatures –20 °C, 0 °C and 45 °C
Rated capacity classification of battery
Table A.4 – End-of-discharge voltage
Voltage specified by the manufacturer
The method of designation of test current I t is defined in IEC 61434
Step 3 – Measure the discharge duration until the specified end-of discharge voltage is reached, and calculate the capacity of cell expressed in Ah up to three significant figures
The test cells must be charged according to the specified guidelines The State of Charge (SOC) adjustment procedure is essential for preparing the cells to achieve the various SOC levels required for the tests outlined in this Annex.
– 28 – Step 1 – The cell shall be charged in accordance with A.3.2
Step 2 – The cell shall be left at rest 25 °C ± 2 K in accordance with A.2.1
Step 3 – The cell shall be discharged at a constant current 1/3 I t (A) at 25 °C ± 2 K for
(100 – n)/100 × 1 h, where n is SOC (%) to be adjusted for each test
Mass energy density (Wh/kg) and volumetric energy density (Wh/l) of cells in a certain current discharge of 1/3 I t (A) shall be determined according to the following procedure a) Mass measurement
Mass of the cell shall be measured up to three significant figures b) Dimension measurement
Dimension of the cell shall be measured as specified in A.2.3 c) Capacity measurement
Capacity of the cell shall be determined in accordance with A.3.3 d) Average voltage calculation
To determine the average voltage during the discharging phase of the capacity test, integrate the discharge voltage over time and divide by the total discharge duration Record the discharge voltages \( U_1, U_2, \ldots, U_n \) every 5 seconds from the start of discharging, discarding any voltages that cut off before 5 seconds Finally, calculate the average voltage \( U_{\text{avr}} \) using Formula (A.1), rounding the result to three significant figures.
NOTE Values provided by measurement devices may be used, if sufficient accuracy can be achieved
A.4.2.1 Energy density per unit mass
The mass energy density shall be calculated using Formula (A.2) and Formula (A.3) up to three significant figures by rounding off the result
W ed is the electric energy of cell (Wh);
C d is the discharge capacity (Ah) at 1/3 I t (A);
U avr is the average voltage during discharging (V) m ρ ed =W ed (A.3)
– 29 – where ρ ed is the mass energy density (Wh/kg);
W ed is the electric energy of cell (Wh); m is the mass of cell (kg)
A.4.2.2 Energy density per unit volume
The volumetric energy density shall be calculated using Formula (A.4) up to three significant figures by rounding off the result
V ρ evlmd =W ed (A.4) where ρ evlmd is the volumetric energy density (Wh/l);
W ed is the electric energy of cell (Wh);
The volume of prismatic cells is calculated by multiplying the total height (excluding terminals), width, and length of the cell In contrast, the volume of cylindrical cells is determined by the product of the cylindrical cross-sectional area and the total length (excluding terminals).
A.5 Power density and regenerative power density
The test shall be carried out in accordance with the following procedure a) Mass measurement
Mass of the cell shall be measured up to three significant figures b) Dimension measurement
Dimension of the cell shall be measured as specified in A.2.3 c) Current-voltage characteristic test
Current-voltage characteristics shall be determined by measuring the voltage at the end of the 10 second pulse, when a constant current is discharged and charged under the conditions specified below
1) SOC shall be adjusted to 20 %, 50 %, and 80 % according to the procedure specified in A.3.4, and the cell temperature at test commencement shall be set to 25 °C ± 2 K For testing of cell at 45 °C ± 2 K, 0 °C ± 2 K and -20 °C ± 2 K, SOC shall be adjusted to
2) The cell is charged or discharged at each value of the current corresponding to the respective rated capacity level in accordance with Table A.5 and Table A.6, and the voltage is measured at the end of the 10 second pulse The upper limit of charge and discharge current shall be 200 A The range of the charge and discharge current shall be specified by the manufacturer, and the standard measurement interval shall be 1 s If the voltage after 10 s exceeds the discharge lower limit voltage or charge upper limit voltage, the measurement data shall be omitted
Table A.5 – Charge and discharge current at the battery temperatures 0 °C, 25 °C, and 45 °C
Rated capacity classification of battery
Ah Charge and discharge current
Table A.6 – Charge and discharge current at the battery temperature – 20 °C
3) Breaks of 10 min duration shall be provided However, if the cell temperature after
10 min does not settle within 2 K, it is allowed to cool further; alternatively, the break duration is extended and it is inspected whether the cell temperature then settles within
2 K The next discharging or charging procedure is then proceeded with
4) The test is performed according to the scheme shown in Figure A.3
D is char ge (+ ) C urre nt (A ) C har ge (– )
Figure A.3 – Test order of the current-voltage characteristic test
(test example with batteries of rated capacity less than 20 Ah)
Discharge current I d, when the power density is calculated corresponding to 20 %, 50 % and
The 80% state of charge (SOC) of rated capacity is determined as illustrated in Figure A.4, utilizing the current-voltage characteristics obtained by measuring the voltage at the 10th second during a constant current discharge test outlined in section A.5.1 The current-voltage characteristic is extrapolated through the least-squares method, allowing for the calculation of the discharge current \( I_d \) corresponding to the discharge lower limit voltage, expressed to three significant figures This discharge current is essential for power density calculations.
Figure A.4 – The method to obtain discharge current I d while calculating the power density
Power shall be calculated according to Formula (A.5) and rounded to 3 significant figures d d d V I
V d is the discharge lower limit voltage (V);
I d is the discharge current obtained from power density calculation (A)
A.5.2.3 Power density per unit mass
Mass power density is calculated from Formula (A.6), and is rounded to 3 significant figures
P d is the power density (W/kg);
M is the weight of cell (kg)
A.5.2.4 Power density per unit volume
Volumetric power density shall be calculated from Formula (A.7), and is rounded to 3 significant figures
P d ｖ is the volumetric power density (W/l);
V 1 is the volume of cell (l)
The volume of a prismatic cell is calculated by multiplying its height (excluding terminals), width, and length In contrast, the volume of a cylindrical cell is determined by the area of its cross-section multiplied by its length (also excluding terminals).
A.5.3 Calculation of regenerative power density
Charge current I d, when the regenerative power density is calculated corresponding to 20 %,