The design verification of energy storage systems is an important step in ensuring the safe and reliable operation of the system, which is crucial for ensuring system performance, extending service life, and protecting the safety of users and equipment.
1 Short circuit test
During the production, assembly, after-sales maintenance, or use of battery modules, there is a high possibility of misoperation due to the large number of modules and connecting wiring harnesses, which can lead to external short circuits in the battery. Although the voltage level of the battery module is low, a current of several thousand amperes can also be generated during the short circuit, instantly releasing huge energy and posing a danger of fire and explosion, seriously endangering the safety of personnel and systems.
The short-circuit performance test of battery modules generally requires the test object to be in a fully charged state. The positive and negative poles of the battery module should be short circuited externally for 10 minutes, and the external line resistance should be less than 5. Observe for a period of time (usually lh) after a short circuit, and use whether there is expansion, leakage, smoke, fire, or explosion after the short circuit test as a technical indicator
2 Squeezing test
There is a risk of compression during transportation and assembly of battery modules, which may cause short circuits in the battery. Both internal and external short circuits can easily lead to fire and explosion. Therefore, compression testing is one of the most direct detection methods for reflecting product performance.
The compression test of battery modules generally requires the tested object to be in a fully charged state, and the compression direction should be the same as the direction in which the battery module is most susceptible to compression in the energy storage system layout. If the direction most susceptible to compression is not available, pressure should be applied perpendicular to the direction in which the battery cells are arranged. After the compression test, observe for a period of time (usually lh) to assess the compression test of battery modules based on whether there is expansion, leakage, smoke, fire, or explosion after the compression test as technical indicators.
3 Drop test
There is also a risk of falling during transportation and assembly of battery modules. Compared to compression testing, the risk level of battery module falling is relatively low. Battery module falling usually causes deformation or shell rupture of certain cells in the battery module, affecting battery performance or leading to leakage, which has an impact on subsequent use and safety hazards. However, battery modules usually do not immediately catch fire or explode after falling.
The compression test of battery modules generally requires the tested object to be in a fully charged state. The positive or negative terminal of the battery module should be freely dropped from a height onto a cement floor, and the battery module should be observed after the test. Assess the performance of battery modules based on technical indicators such as expansion, leakage, smoking, fire, and explosion after drop testing
4 Salt spray and high temperature and humidity test
The operating environment of energy storage systems is complex. If used in seaside or high temperature and high humidity environments, battery modules are prone to rusting, which affects the structural strength of the module and subsequently affects the normal function and safety of the product. Therefore, it is necessary to conduct salt spray and high temperature and high humidity tests on battery modules.
Salt spray testing is an environmental test that uses artificial simulation of salt spray environmental conditions to assess the corrosion resistance of products or metal materials. It can be divided into two categories: one is natural environmental exposure testing; Another type is the artificial acceleration simulation of salt spray environment test.
The salt spray and high temperature and humidity test of the battery module generally requires that the object to be tested is in the fully charged state, and the battery module is subject to multiple spray storage cycles and high temperature and humidity storage. Generally, the performance of the battery module is assessed based on whether there is expansion, leakage, smoke, fire and explosion during the salt spray and high temperature and humidity test.
5 Thermal runaway diffusion test
The accident where an electrochemical cell heats up its temperature uncontrollably through self heating is called thermal runaway. When the heat generated by a thermal runaway battery exceeds the amount of heat it can dissipate, further accumulation of heat may lead to explosions and gas release, which in turn can cause fires. If one battery cell experiences thermal runaway in the battery system, causing thermal runaway in other cells, it is called thermal runaway diffusion.
The thermal runaway diffusion test of battery modules generally requires the tested object to be in a fully charged state. One of the two methods, overcharging or heating, can be selected as the thermal runaway triggering method. The battery cell that can achieve thermal runaway triggering should be selected as the thermal runaway triggering object, and the heat generated by thermal runaway should be easily transferred to adjacent battery cells. For example, the battery cell closest to the center position in the battery module or the battery cell surrounded by other battery cells and difficult to generate thermal radiation should be selected.
During the testing process, battery voltage drop, battery temperature, and temperature rise rate are usually used to determine whether a battery cell thermal runaway has occurred. When a battery cell adjacent to the trigger object experiences thermal runaway, it is determined that the battery module has experienced thermal runaway diffusion. If a fire or explosion occurs during the thermal runaway triggering process and within 1 hour after the triggering is completed, the test should be terminated and judged as thermal runaway diffusion of the battery module.