2000Hz Battery Test Equipment UN38.3 EV Battery Vibration Testing

 EV Battery Vibration Testing UN38.3  for EV Battery Testing 

Lithium-ion batteries are gaining popularity as the most common battery type used for electric vehicles. During their lifespan, these batteries undergo a variety of vibrations and temperature changes. Several common test standards have developed to simulate the long-term environmental effects on these batteries across different size levels (e.g. cell, module, pack).

Of the many test standards for EV batteries, this post will specifically focus on the vibration and temperature aspects of four well-known standards: SAE J2380, SAE J2464, IEC 62660-2, and UN 38.3.

Crystal Instruments Spider systems can provide solutions for random, sine, and shock vibration test, as well as temperature control.

Based on the different load spectrums applied, vibration testing can generally be divided into the following types:

• 1.1 Sine Vibration
  Sine vibration is a type of vibration that changes according to a sine (or cosine) function over time, exhibiting periodicity. Sine vibration can be divided into two types: fixed-frequency vibration and sweep-frequency vibration. A test where the vibration frequency remains constant is called a fixed-frequency vibration. This type of vibration generally simulates the vibration caused by fixed-speed rotating machinery or the vibration at the natural frequency of a structure. Fixed-frequency vibration is mainly used to test the resistance to resonance frequency vibration and predetermined frequency vibration. Sweep-frequency vibration involves changing the frequency according to a specific rule, and it can be categorized into linear sweep and logarithmic sweep based on the sweep speed. The frequency change in linear sweep is linear, meaning it covers a certain number of hertz per unit time, expressed in Hz/s or Hz/min. This type of scanning is used to fine-tune the resonance frequency in tests. Logarithmic sweep frequency changes according to a logarithmic pattern, with units like Oct/min or Oct/s, where “Oct” represents an octave. Logarithmic scanning means that the number of octaves covered in the same amount of time is the same, resulting in slower sweeps at low frequencies and faster sweeps at high frequencies. Sine vibration test conditions include the test frequency range, test level (acceleration amplitude), sweep speed and duration, and test direction.
• 1.2 Random Vibration
  Random vibration⇱ is a type of vibration with an irregular time-domain waveform, where the instantaneous value at a given moment cannot be determined, and the waveform changes randomly over time. The vibrations encountered during transportation and actual use are mostly random vibrations, such as the vibrations generated when a vehicle travels on a road, vibrations caused by aircraft noise on the aircraft structure, and vibrations generated by atmospheric turbulence on wings. Therefore, random vibration testing better reflects the vibration resistance of products. Random vibration cannot be accurately expressed as a time function, so its amplitude and frequency cannot be determined at any moment. However, random vibration can be statistically expressed. It is usually described in the frequency domain, and the test conditions for random vibration testing (severity level) generally consist of the following four components:
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• Test frequency range (Hz): The frequency range refers to the frequency between the highest and lowest frequencies at which vibration effectively excites the product.
  Power spectral density (PSD): Power spectral density describes the energy distribution of vibration per unit frequency.
  Total root mean square acceleration (Grms): Grms is the integral of the PSD over the frequency range, representing the root mean square value, which is commonly used to control and detect test errors.
  Test duration and direction.
  1.3 Mixed-mode Vibration
  Mixed-mode vibration generally involves the superposition of sine and random vibrations, such as random-on-random, sine-on-random, sine-on-random-on-random, and so on.
• Vibration Testing for EV Battery Packs
• 2. Comparison of Battery System Vibration Standards
  Vibration testing is a crucial method for evaluating the performance of power battery systems. Most testing standards for battery systems include vibration tests. The national mandatory standard GB38031⇱, issued in 2020, clearly defines the methods and requirements for vibration testing of power battery systems. The relevant standards for vibration testing of battery systems in both domestic and international contexts are as follows:
• 2.1 International Standards
  USABC 1996 “Battery Test Manual for Electric Vehicles” is an early battery testing standard established by the United States Advanced Battery Consortium. The vibration test in this standard has been referenced by later standards such as USABC1999 “Abuse Testing Manual for Electrochemical Energy Storage Systems” and Freedom CAR “Abuse Testing Manual for Energy Storage Systems in Electric and Hybrid Electric Vehicles.”
• SAE J2380⇱, developed by the Society of Automotive Engineers (SAE), includes a vibration test widely used domestically. J2380 refers to the USABC’s random vibration test to simulate the vibrations induced by road surface irregularities on batteries used in new energy vehicles, assessing their vibration resistance. The vibration test requirements of J2380 have been referenced by SAE J2929 and UL2580 from Underwriters Laboratories. This standard provides two optional vibration test levels, with different test durations for each level.

3. Vibration Testing of Power Battery Systems
3.1 Vibration Table
Vibration testing is generally conducted using a vibration table, which can be mechanical, hydraulic, or electric. Electric vibration tables are the most widely used, with a broad working frequency range, good vibration waveform, and easy control and operation, generally meeting the requirements for vibration tests above 2Hz. The working principle of the electric vibration table is shown in Figure 1. Test conditions are set via computer control software, and the vibration controller sends drive signals to the power amplifier, which amplifies the signal and drives the vibration table to start vibrating. The acceleration sensor collects the vibration signals from the control point and feeds them back to the controller. The control software automatically adjusts the drive signal based on the feedback to ensure that the vibration load on the sample matches the target spectrum. Before conducting a vibration test, it is necessary to verify that the vibration table’s capacity meets the test requirements. The main parameters of the vibration table include maximum thrust, maximum acceleration, maximum speed, maximum displacement, and frequency range.

Vibration Testing for EV Battery Packs

3.2 Test Fixtures
Power battery systems are usually fixed to the vibration table using specially designed fixtures. The main function of the fixtures is to secure the sample to the table and transmit the vibration load from the table to the test sample without distortion. Therefore, the following requirements are placed on the fixtures used for power battery systems:

The fixtures should simulate the battery system’s installation state on the vehicle as closely as possible. The battery systems on vehicles are typically installed using flat, suspended, or press-fit methods. For example, battery systems used in electric buses and special-purpose vehicles are mostly standard box-type battery packs, usually laid flat on the chassis and secured with bolts. Most battery systems used in passenger vehicles are suspended from the chassis by lugs, while some quick-change battery systems are press-fitted onto the vehicle. Therefore, the fixture’s method of securing the battery system, bolt specifications, and torque requirements should match those of the actual vehicle to simulate the real load conditions.
Fixture stiffness and mass: The fixture for the battery system must have sufficient stiffness to ensure the vibration load is transmitted without distortion. At the same time, the fixture’s mass should be minimized as much as possible since excessive fixture weight can affect the vibration table’s load capacity and thrust. Therefore, appropriate materials and processes should be chosen for fixture manufacturing.
Fixture’s natural frequency: The first-order natural frequency of the fixture should be higher than the test frequency range to avoid resonance during vibration, which could affect the load on the sample. The fixture’s frequency response characteristics should be flat over the entire test frequency range, and resonance coupling between the fixture and the sample should be avoided.
Fixture’s lateral movement should be minimized.

• UN 38.3 is primarily used to simulate the vibration loads experienced by lithium batteries during transportation. The vibration test in this standard is conducted with sweep-frequency vibrations in the X, Y, and Z directions, and the vibration test level varies depending on the weight of the sample (12kg).

SAE J2380
The SAE J2380 standard vibration profiles, based off of actual road measurement data, intends to simulate the effect of driving 100,000 miles on battery packs and modules. The standard calls for a series of random vibration profiles, to be applied across all three perpendicular axes for time periods ranging from 9 minutes to 38 hours each.

SAE J2464
The SAE J2464 standard evaluates abuse tolerance for cells and battery packs, performed to measure the response for any RESS (rechargeable energy storage system). These abuse scenarios are purposefully contrary to the battery's design intent, but can be expected to occur infrequently during field use (i.e. due to negligence, accidents, poor training, etc.)

Of all the test types listed, there are 2 specified test types for thermal shock cycling and shock vibration test. The thermal shock cycling consists of 5 cycles through hot and cold temperatures (70°C to -40°C) with each cycle length for 1 hour at the cell level, 6 hours at the module level. The shock vibration test applies 3 positive and 3 negative direction half-sine shocks in each of the three perpendicular axes.

IEC 62660-2
The IEC 62660-2 standard, also associated with ISO 12405, specifies reliability and abuse testing for electric vehicle lithium-ion cells for use in a variety of battery systems. The vibration test calls for a random vibration test for 8 hours on each plane of the cell, as well as a mechanical shock test (half-sine) in all six spatial directions. The temperature test starts the cell at room temperature, and raises the temperature at 5 K/min until reaching a final temperature of 130°C, staying within 2 K of that target temperature for 30 min. The thermal cycling test calls for 30 test cycles (85°C to -40°C).

UN 38.3
The UN Manual of Tests and Criteria provides information on the test procedures for transporting dangerous goods, with section 38.3 discussing lithium ion batteries. Lithium-ion batteries must pass these tests before being cleared for transport.

Of the 8 total test types listed in the standard, there are 3 specified test types for thermal, vibration, and shock. The thermal test consists of 10 cycles through hot and cold temperatures (72°C to -40°C), followed by 24 hour storage at ambient temperature (20°C). The vibration test simulates the typical vibrations with transporting batteries with a swept sine test over 3 hours for each of the three possible perpendicular mounting positions. The shock test applies 3 positive and 3 negative direction half-sine shocks in each of the three perpendicular mounting positions (totaling to 18 shocks).

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