With the rapid development of new energy vehicles, automotive electrical systems have become more complex, requiring higher performance and reliability of electrical equipment. This standard adds a large number of test items suitable for electric vehicles, such as more detailed DC power supply voltage test specifications, short circuit/overload protection tests, etc., to meet the needs of electrical system testing of new energy vehicles. This article interprets the Electrical Load ISO16750-2 (2023) standard, which can help automotive electrical system products improve in the DV and PV stages.

1. Working mode

Working mode 1

No power supply to the DUT

- Operating mode 1.1: DUT not connected to the wiring harness.

•Operating mode 1.2: DUT simulates the mounting position on the vehicle, connected to the wiring harness.

Working mode 2

The DUT performs electrical operation with the test voltage UB

1. Working mode 2.1: System/component functions are not activated (e.g. sleep mode).

1. Working mode 2.2: System/component with electrical operation and control in typical working mode.

1. Working mode 2.3: System components for electrical operation and control under minimum load.

1. Operating mode 2.4: System/component for electrical operation and control at maximum load.

Working mode 3

The DUT is electrically operated with test voltages U_A and U_X and all electrical connections are made. However, no auxiliary machines (e.g. cooling systems) are installed.

1. Working mode 3.1: System/component function is not activated.

1. Operating mode 3.2: System/component with electrical operation and control in typical working mode.

1. Working mode 3.3: System/component for electrical operation and control under minimum load.

1. Operating mode 3.4: System/component for electrical operation and control at maximum load.

Working mode 4

The DUT is electrically operated with test voltages U_A and U_X and all electrical connections are made. In addition, an auxiliary machine (e.g. cooling system) is installed.

1. Working mode 4.1: System/component function is not activated.

1. Working mode 4.2: System parts with electrical operation and control in typical working mode.

1. Operating mode 4.3: System/component for electrical operation and control under minimum load.

1. Operating mode 4.4: System/component for electrical operation and control at maximum load.

2. Test items

2.1 DC power supply voltage range

Purpose: To verify that the product conforms to the design within the minimum and maximum operating voltage ranges.

Table 1 DC power supply voltage, test condition combination

Table 2 Voltage parameters of DC power supply

Table 3 12V system power supply voltage

Table 4 24V system power supply voltage

Fig.1 DC power supply voltage test curve

Test Method:

Edit the test program according to Table 2 and Figure 1 to place the DUT in the Table 1 environment and run it in the corresponding mode. Then feed the test pulse into the DUT.

2.2 Overvoltage test

2.2.1 Prolonged overvoltage

Objective: This test simulates the failure of the alternator regulator, so that the output voltage of the alternator rises above the normal value, and whether the function of the experimental installation device meets the design requirements.

Table 5 Long-term overvoltage

Test Method:

Place the DUT under the corresponding environmental conditions according to Table 5, and after the DUT temperature stabilizes, set the DUT to 3.4 mode to run, set the corresponding test parameters according to Table 5, and then input the test pulse into the DUT.

2.2.2 Jump start

Objective: To start the vehicle with another car and jumper cable when the battery of the car is depleted, and to simulate whether the function of the car is in line with the design when the car is jump-on.

Fig. 2 Instantaneous overvoltage

Table 6 Jump start

Test Method:

The DUT is placed under the ambient conditions in Table 6, and after the DUT temperature is stable, the DUT is set to 2.2 or 3.2 mode to run, and the corresponding test parameters are set according to Figure 2 and Table 6, and then the test pulse is input into the DUT.

Fig. 3 Instantaneous overvoltage

Table 7 Instantaneous overvoltage

Test Method:

Connect the DUT and set the 3.4 mode, set the corresponding test parameters according to Figure 3 and Table 7, and then input the test pulse into the DUT.

2.3 Superimposed AC voltage

Objective: To examine the immunity of DUT to ripples in on-board systems, such as those caused by alternators or DC/DC converters.

Fig. 4 Superimposed AC voltage

Table 8 Superimposed AC voltage

Table 9 Superimposed AC voltage

Figure 5 Superimposes AC voltage

Test Method:

Reference test: Connect the DUT according to Figure 5, set the DUT to 3.3 mode, and set different test frequencies and UPPs according to Figure 4, Table 8 and Table 9; Adjust the UR to reach the corresponding target value or the maximum limit of Ipp; and record the UR.

Voltage Wenbo Test Test: Set the DUT to 3.2 mode, and set the test parameters according to Figure 4, Table 8 and Table 9 and the UR in the reference test.

2.4 Slow-down and slow-rise of power supply voltage

Purpose: To simulate whether the function of the battery is in line with the design under the condition of slow discharge and charging.

Fig.6 Slow down and rise of power supply voltage

Test Method:

Connect the DUT and set the 3.2 mode to set the voltage from UA to slowly decrease (0.5±0.1mv/min or no more than 25mV in equal steps) to 0V as shown in Figure 6, and then slowly increase to UA.

2.5. Voltage transient change

2.5.1 Transient voltage drop

Objective: To simulate whether the function is in line with the design under the influence of blowing fuses in other circuits

Figure 7 12V system - transient voltage drop

Fig.8 24V system - transient voltage drop

Test Method:

Connect the DUT and set the 3.4 mode, set the voltage according to Figure 7 or Figure 8, and apply the test pulse to the DUT's active input at the same time. The rise and fall time should not exceed 10 ms.

2.5.2 Micro-interruptions

Purpose: This test simulates the effects of supply voltage micro-interruption events caused by a short or open power line, such as a faulty contact, a relay defect, a relay contact bounce, or switching from the main to a few redundant power sources.

Figure 9 Micro-interrupt - variable interrupt

Table 10 Micro-interrupts - variable interrupts

Table 10 Micro-interrupts - variable interrupts

Table 11 Micro-interruption - variable recovery

Test Method:

Connect the power supply to the microsecond switch and DUT, set the DUT to 3.4 mode, and edit the microsecond switch according to Figure 9, Table 10, Figure 10, and Table 11.

2.5.3 Reset performance when voltage drops

Purpose: To simulate whether the reset function is as designed in the case of voltage drops. This test verifies the reset behavior of the DUT at different voltage drops. This test is suitable for devices with reset capabilities, such as those containing microcontrollers.

Figure 11 Reset performance when voltage drops

Test Method:

The DUT operating mode is 3.4, when the DUT is working in Usmin, reduce the supply voltage to 95% of Usmin for at least 5s, then increase it to Usmin again for at least 10s; then continue to reduce the supply voltage to 90% of Usmin, repeating the above steps, reducing it by 5% each time until it is 0V.

2.5.4 Start the pulse

Objective: This test verifies the behavior of the DUT during and after startup, simulating whether the DUT functions in accordance with the design during the startup phase.

Figure 12 Starting pulse

Table 12 Starting pulse-12V system

Table 13 Starting pulse-24V system

Test Method:

The DUT operating mode is 3.2, and the start-up characteristic test pulse is applied 10 times on all relevant inputs (connections) of the DUT at the same time. The recovery time between each start-up cycle should be ≥ 2s until the DUT is 100% operational.

2.5.5 Load Throwing

Purpose: This test simulates the load dump transient that occurs when a discharged battery is disconnected when the charge current is generated by the alternator, when there are still other loads on the alternator circuit.

Fig.13 Load dumping-Test A-No centralized load dumping suppression

Table 14 Load dumping-Test A-No centralized load dumping suppression

Figure 14 Load dumping - Test B - with centralized load dump suppression

Table 15 Load dumping - Test B - with centralized load dump suppression

Test Method:

The DUT operating mode is 3.4, and the pulses of Figure 13, Table 14, or Figure 14, Table 15 are applied to the DUT.

Summary: By stipulating a series of strict electrical load test items, such as power supply voltage micro-interruption, reset behavior when voltage drop, starting characteristics, load dumping and other tests, it can simulate extreme situations such as instantaneous power interruption and voltage fluctuations that may be encountered in actual use, evaluate the adaptability and durability of on-board electrical equipment, and improve the reliability of products in actual use. In addition to the above-mentioned test items, there are also reverse voltage, ground offset and power offset, as well as open circuit tests, multi-line interrupts and other tests, the rest of the content will be presented in the next article, so stay tuned.