The activation stage of lithium battery pack includes precharge, formation, aging, constant capacity and so on. There are two main factors influencing the performance of lithium battery pack, namely aging temperature and aging time. What’s more, it is important that the battery tested in the aging test chamber is in a sealed state. If it is a battery on, the data for the test will be very different, which needs to be paid attention to.

Aging generally refers to the placement of the battery after the first charging after the completion of liquid injection. It can be aging at room temperature or at high temperature. Its function is to stabilize the properties and composition of the SEI film formed after the first charging. The aging temperature is 25℃. High temperature aging varies from factory to factory, some of which are 38℃ or 45℃. Most of the time is controlled between 48-72 hours.

Effect of aging test on lithium battery pack

First effect is to make the electrolyte soakage better, which is conducive to the stability of lithium battery pack performance;

Second, after aging, the active substances in the anode and cathode materials can accelerate some side effects, such as gas production, electrolyte decomposition, etc., which can quickly stabilize the electrochemical performance of lithium battery pack;

The third is to select the consistency of lithium battery pack after aging for a period of time. The measured value will deviate from the actual value due to the unstable voltage of the cell after formation, and the voltage and internal resistance of the cell after aging are more stable, which is convenient to select the battery with high consistency.

The battery performance is more stable after high-temperature aging. Most lithium battery manufacturers adopt high-temperature aging operation mode in the production process, and the temperature is 45℃-50℃ aging for 1-3 days, then set aside at room temperature. After high temperature aging, potential adverse phenomena of batteries will be exposed, such as voltage change, thickness change and internal resistance change, which directly test the safety and electrochemical performance of these batteries.

Temperature has a great influence on the cycle aging rate of lithium batteries. At lower temperature, the cycle life is reduced due to the enhanced lithium plating; High temperature can shorten the battery life due to the aging reaction driven by Arrhenius; Therefore, the best cycle life of lithium battery pack can be obtained only at appropriate temperature.

In fact, the real acceleration of lithium battery pack aging is not fast charging, but your charging habits! Fast charging will accelerate the aging of batteries. With the increase of usage times and time, aging of lithium batteries is inevitable, but good maintenance methods can prolong the service life of batteries.

How to select high temperature aging room equipment for lithium battery aging?

Lithium batteries need high temperature aging room for high temperature aging, low temperature and temperature cycling. Under various temperature conditions and changes, they are integrated with the charging and discharging system to carry out overcharge, discharge and short circuit tests at various temperatures. It is evaluated that joule heat accumulation will occur during the test process of lithium batteries, resulting in the temperature rise of batteries, and the risk of thermal runaway of internal materials of batteries, Once the battery thermal runaway and combustion.

In order to ensure the safety of lithium battery pack during various temperature changes and charge discharge related tests, a remote camera can be set up through the window to monitor the test and detect the surface temperature of each battery. If there is abnormal temperature rise on the surface of the battery, it is very likely to be dangerous. The system immediately starts the safety protection mechanism, assuming that when the battery explodes instantaneously, The high-strength inner furnace can withstand the explosion power, and the standard explosion-proof hole can also vent the explosion pressure. The special testing machine for lithium battery will detect its fire state, and immediately put out the fire and cool it down. After the fire is put out, the organic volatile gas and odor gas in the box will be discharged through the exhaust mechanism, so as to ensure the cleanliness of the laboratory, Through a number of international standards required by the lithium battery safety test, in order to avoid lithium battery explosion, combustion, and other concerns.

To sum up, the high temperature aging test chamber should not only have very powerful hardware facilities, but also meet the international test standards. In addition, the quality of high temperature aging test chamber in the market is uneven, so it is very difficult to choose the high quality and suitable high temperature aging test chamber. If you don’t want to waste too much time and energy, it is recommended to choose DGBELL’s high temperature aging test chamber directly.

DGBELL’s Temperature Aging Test Chamber is widely used for the aging test for electronic products, solar panel, plastic products, especially for battery temperature aging test.

Characteristics

• Outside SECC steel, fine powder coating treatment. Inner SUS#304 stainless steel.
• Use new heat resistant long shaft motor.
• Turbine fan.
• Silicone forced tight.
• Over-temperature protection, super load automatic power system.
• Circulation system: air force level cycle.
• Heating system: PID + S.S.R.
• Safety timer: when the temperature reaches a certain height and exceeds the set time, the alarm indicator of the device will be on quickly to warn the tester.
• For the glass window that can observe the interior of the test chamber, we can customize the design on the original conventional products according to the special needs of customers. It can well reflect our strength of product customization in many aspects.

The above is only the main features of the product, for the hardware of the equipment has been more complete description, can carry out a complete process of lithium battery aging test. Believe that this is enough to remove most of your doubts. More specific equipment parameters can be accessed on the official website of DGBELL. If necessary, please let us know about your needs by email, telephone, etc. We will give product suggestions according to your needs as soon as possible, or provide customized solutions. DGBELL is one of the world’s top manufacturers and suppliers of battery safety and stability test chamber. All products are sold at factory price. Please feel free to purchase. Welcome to your inquiry.

This passage summarizes the mechanism of thermal runaway and preventive measures, which have been applied in the design and manufacturing of all battery systems. However, in practice, different material systems have different chemical characteristics, so the thermal runaway mechanism of the battery core is different. Different system designs will also lead to different system-level risks and different solutions.

Among them, the explosion is the power battery system is more common harm performance, caused by the impact, is more serious, not only will cause property loss and environmental damage, or even cause personal injury or life danger.

Possible causes of combustion or explosion of a power battery system are:

The exothermic side reaction of the power battery (cell) leads to thermal runaway and ignites the electrolyte and other combustible substances;

1、The local connection resistance of the high voltage circuit of the power battery system is too large, and when a large current flows through it, the temperature rises to the ignition point temperature, igniting the combustible material inside the power battery system.

2、External short circuit: the combustion explosion caused by the external short circuit of the battery below 1Ah is not common. It is usually swollen or burnt off the pole ear, and the combustion is caused by the external short circuit of the power battery or large capacity mobile phone battery. Some users mistakenly use batteries – metal outer ear insulation, don’t consider when smoking will appear at the scene of the installed battery, combustion of abnormal situation, power battery structure fixed measures also common failures (ill-considered), in the process of users, the battery pack battery external insulation protective film damage caused by the swaying or cables damaged skin, eventually lead to short circuit burning, The internal temperature of the power battery system continues to rise, reaching the ignition point temperature, igniting the internal combustible material.

3、Internal short circuit: structure or process defects lead to pole ear insertion, too little diaphragm wrapping surplus, burr, etc. Polar ear insertion often occurs in the structure of the rear battery and internal parallel, the insulation of the pole ear is not in place, and it is easy to lead to internal acute short circuit and combustion or explosion in the subsequent product protection plate or the use process, but now this situation is relatively rare, in addition to external force factors.

According to the analysis of the use of electric vehicles, the probability of the first situation is high and the risk coefficient is also high. The thermal runaway caused by the exothermic side reaction of the battery cell is the main reason for the combustion or explosion of the power battery system.

The main exothermic reactions in lithium-ion batteries are:

The temperature range of ESI film decomposition is 90~120℃.

The reaction temperature of negative electrode and electrolyte reaches above 120℃;

Electrolyte decomposition, the temperature is about 200℃;

The reaction between the positive electrode and the electrolyte is accompanied by the decomposition of the positive electrode and the precipitation of oxygen. The temperature range is 180~500℃.

The negative electrode reacts with the binder at about 240 degrees.

Core thermal runaway (combustion, explosion) is the root cause of the exothermic side reaction inside the cell lead to heat accumulation, the external heat exchange rate of the cell is less than the rate of heat accumulation, the temperature continues to rise, directly to the ignition point temperature, causing combustion and explosion.

The thermal process inside the cell follows the conservation of energy: Qp = Qe + Qa

In the formula, Qp is the heat generated by various negative reactions inside the cell, Qe is the heat exchanged between the cell and the environment, namely the heat dissipation, and Qa is the heat absorbed and accumulated by the telecom itself. If QE ≥ QP, QA is negative or zero, the temperature inside the cell will not rise and thermal runaway will not occur.

It can be seen from the above analysis that if the exothermic side reaction inside the cell can not be blocked, the temperature inside the telecommunication will rise until the thermal runaway event occurs.

If you want to reduce the risk of battery explosions, you can take the following steps:

1、Take necessary protective measures to reduce the occurrence probability of external sudden factors. For example, select professional battery testing equipment to conduct professional battery tests such as overcharge, over-discharge, overheating, short circuit, extrusion, puncture and so on. Among them, it is recommended to use the battery charge and discharge tester to test the overcharge and over-discharge of the battery. Battery short circuit test is recommended to use the battery internal and external tester; Battery extrusion, puncture is recommended to use a needle testing machine. Of course, according to the different size of the battery, it is necessary to choose the appropriate size of the battery test machine, if the battery pack test needs to use the walk-in battery test machine.

2、Blocking the positive feedback process of exothermic side reactions, such as using Bunding fuse process in PACK module, or adding PTC material between positive and negative electrode materials and fluid collector;

3、reduce the heat generated by exothermic side reactions, such as the choice of lithium iron phosphate cathode material, change the organic solvent composition of the electrolyte, etc.;

4、improve the ignition point temperature, such as adding flame retardant materials in the electrolyte, the selection of ceramic diaphragm, etc.;

5、 improve the heat dissipation capacity, avoid heat accumulation, such as Lilang battery using efficient liquid cooling design, there are individual solutions to the whole battery, immersed in the coolant.

The thermal runaway mechanism and preventive measures summarized above have been implemented in the design and manufacturing of all battery systems. However, in practice, different material systems have different chemical characteristics, so the thermal runaway mechanism of the battery core is different. Different system designs will also lead to different system-level risks and solutions.

Last but not least, GDBELL is one of the top environmental test chamber manufacturers and battery testing equipment suppliers, we focus on test chambers for 15+ years, all test chambers are factory straight out, affordable, and products can be customized.

About salt spray test

The salt spray corrosion test can evaluate the ability of salt spray corrosion to materials and their protective layers, and the comparison of process quality of similar protective layers, and also the ability of some products to resist salt spray corrosion. It is mainly used for the corrosion test of parts, electronic components, metal materials and industrial products.

Salt fog test is mainly to test the influence of salt fog environment on the product in atmospheric corrosion environment, and provide data reference for product optimization.

The environmental effects of salt fog can be divided into three categories: corrosion effect, electrical effect and physical effect.

• Corrosion effect: electrochemical reaction corrosion, accelerated stress corrosion, acid-base corrosion
• Electrical effects: salt deposits damage electrical equipment, produce conductive coatings, insulation materials and metal corrosion
• Physical effect: corrosive substances affect the operation of moving parts, resulting in coating bubbles

As long as the product will be affected by one or more of the effects, it is necessary to carry out salt fog test. In the test, the salt fog environment tolerance of the product can be further understood. In the future, the product can be optimized through data analysis to improve the environmental reliability of the product.

With the improvement of environmental testing standards, salt fog environmental testing as an important part of environmental and climate detection has also been challenged seriously. Simple salt fog test equipment has been unable to meet the increasing demand of detection accuracy. More and more environmental detection equipment manufacturers have begun to increase research and development, and more complex salt fog test equipment is launched.

The influencing factors of salt spray test

• Test temperature and humidity

Temperature and relative humidity affect the corrosion of salt fog. The critical relative humidity of metal corrosion is 70%, and when it reaches or exceeds, salt fog will be deliquescence into electrolyte with good conductivity. When the relative humidity decreases, the concentration of salt solution will increase until the crystalline salt is produced, and the corrosion rate will decrease.

The higher the test temperature, the faster the corrosion rate of salt spray is, because the temperature increases, the molecular motion is intensified, and the chemical reaction is accelerated. Of course, it is not that the higher the temperature is, the better, the scientific research test, for the neutral salt spray test, 35 ° C is the most appropriate, the mechanism of salt spray corrosion is closest to the actual corrosion environment, and the data reference value is very great.

•  Concentration of salt solution

The influence of salt concentration on corrosion rate is related to the types of materials and coatings. For steel, nickel and brass, the corrosion rate is faster than 5% while the corrosion rate is higher than 5%. This is caused by the relative change of oxygen content in salt solution, which will directly affect the depolarization ability of oxygen, namely corrosion. However, for metals such as zinc, cadmium and copper, the corrosion rate is always accelerated with the increase of salt solution concentration.

•  Placement angle of sample

The placement angle of the sample has a significant influence on the corrosion test results. The settlement direction of salt fog is close to the vertical direction, the corrosion effect of the sample is the largest when placed horizontally, while the vertical position is the smallest. The suitable product placement angle can be selected according to the standard requirements.

•  pH value of salt solution

The pH value of salt solution is one of the main factors that affect the salt spray test. The lower the pH value, the higher the concentration of hydrogen ions in the salt solution, the stronger the acid, the stronger the corrosiveness.

About walk in complex salt spray test chamber

Walk in complex salt spray test chamber is one of the series equipment of environmental reliability test. The main test objects are metal equipment, electronic equipment, battery, coating, etc. many products or materials that will be affected by the environmental effects of salt spray during transportation and use. The main function is to simulate the salt fog corrosion environment in natural environment by artificial simulation in a certain volume space. Because the salt fog test period in natural environment is long, this professional test equipment is designed and adjusted to make the salt concentration of chloride in salt fog environment reach several or dozens times of the salt fog content in the general natural environment, The corrosion speed is greatly improved to accelerate the corrosion process of salt spray corrosion environment on the test object, and the temperature controllable function is increased. It can simulate some extreme test environment, and get accurate test data faster.

As a kind of composite salt fog test equipment, it is mainly used for alternating salt fog test. Alternating salt spray test is mainly the alternating cycle test of salt fog environment, constant temperature and humidity environment and dry environment. Sodium chloride solution is evenly sprayed in the box, and the primary salt spray corrosion of the test object of the box lasts for one cycle, and then a period of salt solution settlement corrosion is carried out under the set constant temperature and humidity environment, The salt concentration of sodium chloride solution in dry environment is gradually increased during the process of environmental transformation, and the salinity corrosion efficiency of the test object is improved. If the test object has higher requirements for the corrosion resistance environment, the cycle times of the test can be increased to achieve the test goal. Through such an alternate salt fog erosion test, the salt fog environment in the box can greatly simulate the environmental effect of salt fog corrosion in nature on the environmental effects of the test object, and obtain more complete and accurate test data.

Equipment parameters

Walk in Complex Salt Spray Test Chamber

Conventional model BE-8209, divided into 12m ³ And 15m ³ Two internal dimensions

Temperature control range: 0 ° C～+85° C. Fluctuation ±0.5° C

Humidity control range: 30% – 98% R.H. fluctuation ± 3%R.H.

Resolution Temperature: 0.01 ° C. Humidity: 0.01% RH

Spray Capacity 1~2mL/80cm²/hr (Collect at least 16 hours, take the average )

Spray Pressure 1.00 ± 0.01kgf/cm²  Spray Solution pH Neutral 6.5～7.2 Acidity 3.1～3.3

The above is part of the walk in chamber for complex salt spray test. If you need to know more about it, please visit our official website https://belltestchamber.com/. Our engineering team is strong enough to meet your customization needs. Please contact us if necessary.

6 Facts About Vibration Testing Systems

Vibration problem exists widely in the popular life and production, buildings, machines or the outside world will produce vibration under the incentive. And mechanical vibration often damages the normal work of machinery, and even reduces the service life of machinery and causes irreversible damage to the machine. Most of the mechanical vibration is harmful. Therefore, the study of vibration is not only conducive to improving the living environment and living standards, but also helpful to improve the service life of mechanical equipment. Mechanical vibration testing technology plays a very important role in industrial production, manufacturing efficient mechanical vibration testing system has become an important content of testing technology.

What is mechanical vibration?

Mechanical vibration refers to the process in which the displacement of an observation point on the mechanical equipment or structure changes with time around its mean value or relative datum when the mechanical equipment is in motion. Mechanical vibration is double-sided, beneficial and harmful.

There are two types of vibration, one is steady state vibration and the other is random vibration.

The three elements of vibration (signal three elements) : amplitude, frequency and phase

• Amplitude: Indicator of vibration intensity. Representation method: single peak value, effective value, average value, etc.
• Frequency: the reciprocal of the period. Through spectrum analysis, the main frequency components and their amplitude can be determined, so that the source of vibration can be found and some measures can be taken.
• Phase: The phase information of vibration signal is very important.

Types of vibration tests

1、measure the vibration of the working machinery or structure in the working state, such as: the displacement, speed, acceleration, frequency and phase of vibration, etc.

• Understand the vibration state of the tested object
• Rating
• Find the root cause
• Perform monitoring, analysis, diagnosis and prediction

2、Add some excitation to mechanical equipment or structure to test its forced vibration.

Obtain the vibration mechanical parameters or dynamic properties of the tested object, such as natural frequency, damping, response, mode, etc.

Composition of vibration test system

Vibration testing system is mainly composed of sensor, signal adjustment part, digital to analog converter, signal processing part, data recording part, feedback part and so on.

The sensor is the component that will be measured into some kind of electrical signal, is the most important part of the whole test system. The signal regulation part converts the output signal of the sensor into a form suitable for further transmission and processing. After processing, the original signal is more convenient to analyze and process, and most of the signal conversion is direct conversion of electrical signals. Signal processing part is the signal from the signal regulation link to carry out various operations and analysis, which is also the core meaning of the test. The digital-to-analog converter is the link of the conversion between analog signal and digital signal when the computer is used to test and control the system.

The main function of the test system is to convert the initial test signal into some signal for extraction and analysis more easily and easily. So the most important thing is that the signal is not distorted, that there is no disturbance. This puts forward more strict request to the test system.

Reasons, processes and results of vibration testing of products

First of all, in any product in the design, development stage, it is necessary to carry out vibration test, first, can analyze the vibration mode of the test product in different vibration state, test the ultimate strength of the product and set the relevant characteristic specifications; Secondly, failure analysis and improvement are carried out on the vibration test results of the sample. Full ESS testing is performed while the sample is in production to screen for potential defects in large numbers. (according to the features of the product and scale of vibration in ESS test effectively screen out the potential bad thing, and for electronic or institutions and processing when the residual thermal stress and stress can effectively eliminate them the effect of residual stress and can effectively eliminate the multilayer circuit board between discrete capacitance effect, will provide considerable help to product quality.) The second is to the product quality management (QC) and quality assurance (QA), can effectively ensure and manage the quality of the product level, certification production of the product its use function, specifications and reliability and the same as the label.

Generally speaking, vibration tests can screen out the following defects: Fixed a loose, electronic contact in bad place, screen out the potential of bad parts, filter out any defect in the solder joints, adjust the position of vibration, accuracy of distortion, components of the broken, damaged, abnormal circuit breaking short circuit, the power cord or the signal line of abnormal wear or wire break or loose fall off, specimen vibration noise, contact function failure, etc.

Vibration testing of products can provide the basis and reference for engineering development, process control, quality improvement and promotion, provide the interrelation conditions related to vibration, guarantee the quality of products, reduce maintenance expenses and increase the profit rate, improve the overall image, etc

Standard test requirements related to vibration testing

• IEC62133-2012
• UL1642
• 3
• GB31241-2014

Matters needing attention when using vibration test system

• Temperature and humidity

Do not operate vibration test system equipment outside the temperature and humidity limits; Refer to the relevant user manual.

• high altitude

At higher altitudes, vibrator cooling will be affected by reduced air density. If such problems are likely to arise, it is advisable to consult a professional engineering team for advice.

• cleanliness

The vibration test system and other related equipment shall not be operated in a humid, greasy, dirty or dusty environment. Dirt and dust may cause the central positioning system (if installed) to fail to function properly. Water from wet conditions can corrode the vibrator and may cause a short circuit. Oil on or around the vibrator can make the surface smooth and pose a danger to operators. Therefore, making sure the surrounding area is tidy is an important part of daily maintenance activities.

• condensation

If the operating temperature and humidity (e.g., working in a temperature chamber) bring the temperature of the vibrator moving coil below the dew point, moisture will condense on the moving coil. This can corrode the frame and cause a short circuit. These problems can be avoided by:

• Use heat shield
• Install heating elements around the moving coil/temperature box interface
• Direct the hot air discharged by the fan to the bottom of the temperature box

More knowledge about vibration testing will continue to be updated. If you want to know more about battery testing, environmental testing equipment, etc., you can subscribe to https://belltestchamber.com/. We have a professional engineering team and innovative equipment and look forward to your attention and visit!