With the vigorous development of the electronics industry, various electronic products and electrical appliances have gradually become indispensable tools for people to use, and batteries, which are closely related to them, have gradually attracted people’s attention. The safety of the battery itself is among them. Whenever a battery has potential safety hazards, it becomes a time bomb, endangering people’s lives.
There are many factors that affect battery safety, and the high temperature and high pressure generated inside the battery are directly related to heating factors. There are many factors that cause fever. Certain impact tests generate heat inside the battery, and they can also detect the battery’s impact resistance and its subsequent stability. As a result, the heavy impact test is an important component of battery safety testing.
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1. Test Standards
In the process of battery safety testing, test standards such as UL 1642, UN 38.3, IEC 62133-2012, SJ/T 11169-1998, YD 1268-2003, SJ/T 11170-1998 have different specific test requirements for impact resistance batteries, but the principle is basically the same.
Two heavy-duty impact test hammers (10 kg and 91 kg respectively) are mainly used for free-fall impact tests on batteries. The battery is placed on the platform after it has been fully charged according to the standard’s test method. A metal rod with a diameter of 158±0.2mm or 8mm is placed in the center of the battery on the upper surface of the geometric platform. Use a weight of 9.1±0.1kg or 10kg to impact the surface of the battery with a metal rod from a height of 610mm±25mm, and observe whether it explodes.
The heavy impact test has two meanings. One is that the potential energy of a 9.1 kg hammer falls freely from a height of 610 mm and then transforms into kinetic energy to act on the battery. That is, a round rod with a diameter of 158 mm hits the battery instantly after gaining kinetic energy, and the positive and negative electrodes inside the battery are instantly squeezed. If the separator cannot effectively isolate the positive and negative electrodes at this time, it will cause a short circuit between the positive and negative electrodes, which will trigger an exothermic reaction inside the battery, resulting in unsafe conditions.
Another meaning is to check whether the battery will be deformed. The weight of each standard weight is mostly 9.1 kg, only the traditional YD 1268 is 10 kg. The impact height is also a free fall from a height of 610mm, and the metal rod is about 158 or 79mm in diameter. In general, 6 hours are required for observation.
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2. Design requirements
The design requirements of the heavy object impact testing machine include the following points:
- The impact process removes the resistance of the rope, and the accuracy of the lifting height removes the resistance of the rope;
- The electromagnetic device absorbs the heavy hammer, and the lifting height of the heavy hammer is controllable, remote control operation, etc.
- Safety protection device, explosion-proof function, automatic smoke exhaust device, etc. It is easy to cause explosion damage during the test since heavy objects are used mainly to observe if the lithium battery explodes. It is, therefore, necessary to design explosion-proof and observation functions;
- The system should be simple in composition, low in cost, and well-promoted.
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3. Design and technical solutions
In the process of carrying out the heavy object impact test on the battery, it is necessary to lift a certain heavy object to a certain height. After realizing a series of processes such as rapid separation, free fall, and linear impact, the safety performance of the battery can be judged by observing the change phenomenon of the battery after impact.
Rope traction is the main component of the traditional heavy object impact test device. Lift the heavy object to a certain height through motor traction, and then quickly disconnect the traction rope, the weight falls relatively freely with the traction rope and impacts the battery.
The new heavy object impact testing machine adopts an electromagnet to absorb the heavy object lifts the heavy object through the screw rod, and then demagnetizes after power off, so that the heavy object can be separated quickly, and the battery sample can be completely dropped.
1) Test Structure and Principle
The main body of the main engine is composed of a frame, a box body, a control box, and lifting parts. The body of the box is made of explosion-proof materials, and the front explosion-proof door has an observation window. A bottom plate, a top plate, and a lifting guide rod make up the frame. Through the lifting guide rod, the top plate is fixed above the bottom plate; the bottom plate has a place for placing the battery to be tested. The box is equipped with a heavy object for testing the impact of the battery.
There are heavy objects in the test assembly for absorbing and releasing heavy objects, a lifting assembly is arranged above the test assembly, and a correction assembly is arranged above the test assembly. Tube placement at the bottom of the frame: the lifting assembly is installed on the top of the frame; the test assembly is set between the lifting assembly and the straightening assembly and its up and down movement is controlled by the lifting assembly; the test assembly, the lifting assembly, and the positive assembly are all connected to the control box. The tester is powered by electricity and air pressure, and laboratories generally have electricity and air sources. Using electricity and gas as the power source not only reduces costs but also protects the environment.
The specific operation process is as follows: press the suction button, and the heavy object is sucked by the electromagnet, press the lifting button, and the heavy object is lifted to the specified height, press the “release” button on the control panel, the electromagnet is powered off, and the heavy object Release: The heavy object falls freely into the test area. At this time, the heavy object is tilted and cannot be picked up again. It is necessary to press the “Trolley Upright” button and the “Down” button on the control panel to lower the lifting structure to the point where it can be sucked. the height of the weight. Press the “suction” button again, the electromagnetic soldering iron is powered on, and the heavy object is sucked again for testing.
2) Security design
1. Safety device for falling outside the heavy hammer. After confirming that the heavy hammer has been sucked, the safety clip should be clamped to prevent the heavy hammer from accidentally falling off due to unexpected power failure or other unprepared situations.
2. Limit the protection design of the proximity switch and travel switch. When the hammer rises to the specified height, it will stop automatically when it touches the proximity switch. The shock height is determined by adjusting the position of the proximity switch. If the lifting is too high, the lifting device will press the travel switch on the device, and the lifting device will stop to protect the motor.
3) Equipment Innovation Points
The innovation points include the following two aspects: on the one hand, the new heavy object impact testing machine has the characteristics of “electromagnetic”, “cordless traction”, and “automatic reset”; on the other hand, the system can be clamped by pneumatic safety gear to prevent The hammer falls off when the power is suddenly cut off.
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After the device is manufactured, the convenience and accuracy of the battery weight impact test can be further improved. The hazards in the battery testing process are fully considered when designing the equipment.
Therefore, the safety of equipment is the focus of this design. The equipment adopts multiple ways of safety protection, simple structure, simple processing technology, and convenient operation. The equipment has been patented, and the impact test in the actual inspection proves that it has strong practicability and has a good reference value in mechanical inspection and application.