GB/T 44649-2024Nickel-metal hydride cells and modules used for electric road vehicles - Safety requirements (English PDF)

4.1.1 Scope of measurement devices

The instruments / devices used shall be able to accurately measure voltage and current values.

The measuring range of the instruments / devices and the measurement method selection shall ensure the accuracy specified for each test. For analog instruments, readings shall be taken from the later 1/3 of the dial. Any other measurement instruments of equivalent accuracy can be used.

4.1.1.2 Voltage measurement

The accuracy of the instrument used for voltage measurement shall be equal to 0.5 or higher.

The resistance of the voltmeter used shall be at least 1,000 /V.

4.1.1.3 Current measurement

The accuracy of the instrument used for current measurement shall be equal to 0.5 or higher.

The entire assembly of ammeter, shunt and leads shall have an accuracy level of 0.5 or higher.

4.1.2 Tolerances

Relative to the specified or actual value, the overall accuracy of the controlled or measured value shall be within the following tolerance ranges:

a) Voltage 1%;

b) Current 1%;

c) Temperature 2 C;

d) Time 0.1%; e) Dimensions 0.1%.

These tolerances include the comprehensive accuracy of the measurement instruments, the measurement technique used and all other errors during the test process.

4.2.1 Test temperature

the following mode:

---Step 1: before charging, the cell shall be placed at ambient temperature and discharged at a constant current of 1/3 It to the termination voltage specified by the cell manufacturer;

---Step 2: at ambient temperature, charge the cell in accordance with the charging method specified by the cell manufacturer.

5.2 Capacity

Before adjusting the charging status in accordance with 5.3, the rated capacity of the cell shall be confirmed in accordance with the following steps.

---Step 1: charge the cell in accordance with the provisions of 5.1 After charging, the cell temperature shall be stabilized in accordance with 4.2.1.

---Step 2: the cell shall be discharged at 1 It to 0.9 V at ambient temperature. The maximum discharge current is 200 A. When testing a module, the value of the termination voltage is the product of the termination voltage of a cell and the quantity of cells connected in series in the module.

The test method for the current It is as defined in IEC 61434.

---Step 3: measure the discharge duration, until the termination voltage is reached; calculate the cell capacity and retain three significant figures.

5.3 Adjustment of State of Charge (SoC)

The test cell shall be charged in accordance with the following steps. The adjustment of state of charge is the procedure for preparing cells with different states of charge for testing.

---Step 1: charge the cell in accordance with 5.1.

---Step 2: in accordance with 4.2.1, let the cell stand at ambient temperature.

---Step 3: the cell shall be discharged at a constant current of 1/3 It at ambient temperature for (n) h. The current SoC of the cell is n%, which needs to be adjusted for each test.

6.1 General Requirements

Safety tests shall be conducted under conditions specified by the cell manufacturer, using cells or modules that are no more than 6 months old.

In accordance with the agreement between the cell manufacturer and customer, determine the quantity of cells required for each test.

For all specified tests, the test installation conditions, including cell or module safety and wiring conditions, shall be recorded.

NOTE: if necessary, in order to prevent deformation, without violating the purpose of the test, the cells shall be maintained during the test.

6.2.1.1 Test purpose

This test is to verify the safety performance of the cell under inertial loads that may occur in a vehicle collision.

6.2.1.2 Test steps

The test shall be carried out in accordance with the following steps:

---Step 1: in accordance with 5.3, adjust the SoC of the cell for BEV to 100%, and adjust the SoC of the cell for HEV to 80%.

---Step 2: the cell shall be fixed onto the testing machine through rigid structural support. This support will support all surfaces of the cell.

---Step 3: apply a half-sine impact with a peak acceleration of 50 gn (gn represents the standard gravity acceleration, which is 9.80665 m/s²) and a pulse duration of 11 ms to the cell. In three mutually perpendicular installation positions, the cell shall respectively withstand 3 impacts in the positive direction, then, respectively 3 impacts in the negative direction, for a total of 18 impacts.

6.2.1.3 Acceptance indicator

During the test, the cell shall not manifest signs of fire or explosion.

6.2.2.1 Test purpose

This test is used to measure the cell's response to external load forces that may cause deformation.

This test is to simulate the high-temperature environment that the cell will experience during normal vehicle operation and to verify the safety performance of the cell under such conditions.

6.3.1.2 Test steps

Scheme A: the test shall be carried out in accordance with the following steps.

---Step 1: in accordance with 5.3, adjust the SoC of the cell for BEV to 100%, and adjust the SoC of the cell for HEV to 80%.

---Step 2: the cell shall be placed in a box with circulating air. The temperature inside the box is 60 C 2 C, and the cell shall be maintained at this temperature for 2 hours.

Then, lower the temperature to 25 C 2 C and observe the cell in the box for 1 hour.

NOTE: if necessary, in order to prevent deformation, without violating the purpose of the test, the cells shall be maintained during the test. Scheme B: the test steps shall comply with GB 38031-2020.

6.4.1.1 Test purpose

This test is to verify the safety performance of the cell when exposed to external short circuit.

6.4.1.2 Test steps

Scheme A: The test steps are as follows.

---Step 1: the cell shall be fully charged in accordance with 5.1.

---Step 2: the positive and negative terminals of the cell shall be connected through an external resistor for 10 minutes for short-circuit test. The total external resistance of each cell shall be not greater than 5 m and may also be specified by the customer and cell manufacturer.

---Step 3: after completing the above-mentioned test steps, observe the cell at ambient temperature for 1 hour. Scheme B: The test steps shall comply with GB 38031-2020.

6.4.1.3 Acceptance indicator

During the test, the cell shall not manifest signs of fire or explosion.

6.4.2.1 Test purpose

This test is to verify the safety performance of the cell under overcharge conditions. […]