As electric vehicles continue to dominate the marketplace, several safety standard tests are being conducted to keep the vehicle working condition stable. These safety standard tests involve the evaluation of batteries for electric vehicles, with the distinct focus of testing performance, cycle life, and safety. Battery evaluation and testing elective vehicles are multifaceted and require to be subjected inside a test machine for the determination of accurate results.

Testing of electric vehicles aids in determining the future operating condition of the vehicles, which will ensure safety for consumers along with stable usage performance. The testing of electric vehicles involves the evaluation of its components, such as the batteries, charging technologies which can either be AC or DC. This test is important for ensuring that the charging stations and the electric vehicle components can function accurately without any flaws. Testing of electric vehicles along with its components in a test chamber ensures that both battery issues and other potential hazards are fixed at the early stage of development by implementing accurate modules. For battery evaluation, both the battery cells and battery packs are subjected to an intense testing process inside the battery test chamber according to international standard requirements.

Safety Test Methods for Electric Vehicles

There’s no doubt that when operating electric vehicles, accidents like collision, component failures, thermal shock, explosion, etc. In most cases, these accidents can escalate to causing life-threatening damage.

However, after the research by professionals engineers in arranging different safety test methods for electric vehicles, it’s now easy to evaluate and assess different factors related to electric vehicles’ functioning capabilities.  With the assessment and evaluation process of the electric vehicles based on the international safety test methods, the functionality of the electric vehicles is more stable than ever.

Types of Battery Testing

The testing of batteries starts from the voltage to its electrochemical impedance. For improved technology development like electric vehicles, which makes use of strong batteries like the lithium-ion batteries that are in high demand. Evaluation of batteries through the different diagnostics or testing processes is crucial for maintaining stable functionality that will prevent future catastrophic failures and flaws that will endanger consumers.

The testing of batteries requires it to be subjected to different conditions where its symptoms will be evaluated based on the exposed features. For most batteries, the truth to its life cycle, energy capacity, and other functional systems are related to its chemical properties. For example, the li-ion and lead battery system exhibit different chemical features.

Different battery test methods include:

• Voltage test

Testing the voltage of a battery determines the amount of energy it can retain along with its state of charge in an open circuit condition. Determining the battery voltage according to the international safety standard is necessary for battering evaluation in electric vehicles.

• Full cycle test

Full cycle testing batteries involves the charging and discharging of the battery energy to evaluate its capacity. The full cycle test is important for reading and determining battery capacity accurately without errors. Even though this type of test takes a lot of time before completion and requires to be carried out in a test machine by a professional for safety purposes.

• Rapid test

The rapid test involves the battery to be subjected to multiple frequencies to observe the in-flow of its chemical properties. To conduct this test successfully, advanced technology is needed for determining and decoding the algorithm of the battery properties.

• Battery life test

The battery life test is also known as a state of life indicator is crucial for estimating the battery life by reading the number of active coulombs the battery can generate in its life cycle. For a newly developed battery, it starts from 100% to decrease as it generates coulombs until its last number.

Apart from the above-mentioned battery test methods for EVs, there are other testing methods such as ohmic test, read and charge test, etc. For the accurate results to be obtained during these tests, the battery must be subjected to an advanced battery test chamber, where a professional specialist will oversee the entire process.

Relevant standards for Electric vehicles testing

The testing of electric vehicles according to the certified standards has improved the future of transportation by aiding effectively in the production of stable models. Even consumers have nothing to be afraid of because of the relevant standards of testing electric vehicles, which have ensured safety and improved performance.

Testing the capabilities of electric vehicles, with its components such as the batteries and electric motors has boosted the development stage of EVs to its peak. With these tests, integration of safety systems in electric vehicles (EVs) for the prevention of accidents like electrical fires, short-circuits, power issues have been achieved.

Safety Testing – Best Battery for Electric Vehicles

There is no ideal choice of battery for electric vehicles. However, some battery is at the top list in the marketplace as well as efficient for powertrains. The lithium-ion battery, Nickel-zinc battery, and Nickel-cadmium batteries are among the best choices of batteries. Even though lithium-ion batteries have made a breakthrough in providing electric vehicles up to 320-480 km of range per charge. That’s not all because lithium batteries are lighter than Nickel batteries, which makes it the best choice.

Equipment for Testing Electric Vehicles

The testing of electric vehicles requires all of its components to be tested. For an advanced technology like the electric vehicle to be tested, a large testing machine such as the walk-in test chamber will be required. The walk-in test chamber is suitable for testing large and small-size technological components by exposing and cycling it through different temperatures.

Testing Electric Vehicles – Safety and Performance

The testing of electric vehicles guarantees performance and customer safety. As a manufacturer that develops interesting technologies like electric vehicles, there’s no doubt that your goal is ensuring that your products stay at the peak of the competition in the market. However, with the testing of electric vehicles the standard and quality of the development can be determined, which can be crucial for customer’s safety and satisfaction.

How to determine the high and low temperature chamber is qualified equipment?

1. Check whether a double-layer temperature-resistant sealing strip is used as the seal between the door and the test chamber body to ensure the accuracy of the test. The door of the test chamber adopts a non-reactional door handle.
2. The outer test chamber material is made of A3 steel plate, which is pressed by machine tools, which is not easy to cause deformation. The thickness of the steel plate is 1.2mm. The surface is treated with plastic spraying. The inner test chamber is made of SUS304 stainless steel plate and the thickness of the steel plate is 1.0mm, which makes the test chamber beautiful, clean, easy to manage.
3. The use of insulation materials inside the test chamber to ensure that the high temperature will not lead to deformation of the device occurs, to ensure that the temperature inside the working chamber will not be passed to the device outside, so that the temperature inside the working chamber to maintain a stable state.
4. Check whether the various components in the test chambers are damaged or the wiring is off, whether the sample holder has a certain load-bearing capacity, and whether it is welded by high-quality stainless steel.
5. Whether the device has an over-temperature protection system and leakage, short-circuit automatic shutdown after the fault alarm, and other protection.
6. Check the overall equipment external whether there are scratches, test chamber electrical control cabinet line is safe, reliable, neat, can not appear parts line off, etc.

How to make high and low temperature test chamber more energy efficient?

1. Equipment installation and commissioning are complete, the equipment should be placed in a well-ventilated environment, away from the fever light source to avoid direct sunlight, the front and back of the equipment should be left around a certain distance space. (General distance of 70 cm, in order to facilitate the heat dissipation of the test chamber)
2. The working chamber of the test sample bureau test chamber wall should leave a certain distance, the test sample should not slow down, and leave a gap between the test chamber wall, let the air in circulation.
3. In the course of the test to reduce the number of times to open the door, as far as possible to avoid this happening, because open a door compressor needs to run for ten minutes, in order to restore the high and low temperature recovery high and low temperature temperature temperature.

How to choose the high and low temperature test chamber refrigeration mode?

High and low temperature test chamber if you want to achieve the effect of refrigeration, you need to reach through the compressor refrigeration, the compressor is mainly divided into air-cooled, water-cooled, there is another kind of refrigeration for liquid nitrogen, how to choose the high and low temperature test chamber refrigeration mode it, is based on the test temperature is different, the refrigeration mode is also different.

1. “Air-cooled” means the meaning of natural cooling, generally applicable to small power products, if the impact test chamber using the ambient temperature is low or long-term maintained at 5-25 ℃, and have a ventilation device. To ensure that the equipment in the most comfortable working environment, to extend the service life.
2. “Water-cooled” using the fluidity of the water temperature to dissipate heat, according to the impact tester installed on the amount of water equivalent water tower, the general recommendation is 8-16 tons, the water tower can not be put indoor, can only be put on the roof or downstairs, and maintenance also more trouble, the water pipe must be wrapped, or it is easy to sun crack or frostbite, but in the final analysis, in fact! There is no big difference between the two before, both are for heat dissipation, but the heat dissipation is different, mainly according to the customer’s choice and environmental requirements. At the same time, as a manufacturer of high and low temperature impact test chamber, we will also put forward the most reasonable program for you based on field considerations.
3. In industrial production, liquid nitrogen is obtained by fractionation of compressed liquid air, which can be used as a deep refrigerant, and because of its chemical inertness, it can be directly in contact with biological tissues and immediately frozen without destroying biological activity. And the temperature of liquid nitrogen can reach -196 ℃, we have used liquid nitrogen as a refrigerant to replace the compressor in the process of developing environmental test equipment and to improve the technology of the cryogenic chamber. Produce a liquid nitrogen cryogenic chamber.

What are the maintenance methods of the accelerated high and low temperature chamber?

Many users after the use of a fast temperature chamber or other environmental testing equipment are not cleaned, in fact, this will not only cause errors in the next test results, but also may affect the performance and service life of the equipment. If you want a piece of equipment to serve the enterprise for a long time, you need not only the correct use of the method and a piece of good maintenance equipment, otherwise, even if how to use it correctly is also unable to guarantee the service life of the equipment.

The wet ball gauze is a fast-temperature test chamber on the need for frequent cleaning or replacement of accessories, because long-term use will make the gauze yellow hardened, will lead to humidity sensors can not accurately detect the actual humidity in the workplace or the controller humidity display error. So in order to avoid this situation affects the test results, we need to ensure regular cleaning gauze or direct replacement, if it is to replace the new gauze, but also to ensure that the installation is cleaned before.

There is the use of fast-temperature test chamber for testing products, in the test process is needed to link the power cord or other items, need to explain in advance and manufacturers, let them open a test hole in the side of the equipment. Do not enter the test line through the door and product links, because not only will affect the accuracy of the test results, but also have a serious impact on the seal of the test chamber.

Concept overcharging, or overcharging, is a type of lithium-ion battery abuse where the charging voltage of a lithium-ion battery is too high above its charging cut-off voltage. Lithium-ion battery charging usually set charging cut-off voltage, the process needs to use constant current and constant voltage charging method to avoid overcharging the battery. However, in special circumstances, such as BMS damage, malfunction, etc. will lead to overcharging of the lithium-ion battery, resulting in battery performance damage and safety issues. Continuous overcharging at a high rate will lead to an increase in battery temperature and internal pressure, which will have a devastating effect on the performance and appearance of the battery in serious cases, such as leakage, bottom bulging, increased internal resistance of the battery, and shortened discharge time and cycle life.

The principle is well known, the difference between the positive potential and negative potential of the battery voltage. When charging, the positive potential increases, the negative potential decreases.

The reaction formula is as follows:

positive electrode reaction:

negative electrode reaction:

x corresponds to the amount of lithium removed/embedded in the positive electrode/cathode material. The relationship between positive and negative lithium content and voltage and the relationship between battery voltage and positive and negative voltage are shown in Figure 1. 4.2V is the most common full-charge voltage of lithium-ion battery, and the inconsistency will be lower when it is used in a group.

Fig. 1 Relationship between lithium content and voltage of positive and negative electrodes, the relationship between battery voltage and positive and negative electrode voltage

When overcharged, the positive and negative electrolyte inside the battery may participate in side reactions. The side reaction is usually accompanied by a loss of battery capacity and a change in internal resistance, which can lead to high temperatures, flatulence, and ultimately, an explosion. Specifically, the side reactions that occur in different materials are different.

1. graphite cathode over-charge reaction battery in the over-charge, lithium ions are easily reduced deposited on the negative surface: the deposited lithium coated in the negative surface, blocking the embedding of lithium. Lead to the discharge efficiency and capacity loss, the reasons are:

• the amount of circulating lithium reduced;
• deposited lithium metal and solvent or support electrolyte reaction to form Li2CO3, LiF, or other products;
• lithium metal is usually formed between the negative and the membrane, may block the membrane pore to increase the internal resistance of the battery;
• due to the nature of lithium is very active, easy to react with the electrolyte, and consume electrolyte. This leads to a reduction in discharge efficiency and loss of capacity. Fast charging, excessive current density, severe polarization of the negative electrode, lithium deposition will be more obvious. This is prone to occur when there is an excess of positive activates relatively to negative activates. However, at high charging rates, lithium metal deposition may occur even if the ratio of positive and negative reactive species is normal.

2. Anodal overcharge reaction

Anodal overcharging is prone to occur when the ratio of positive to negative active species is too low relative to the negative active species.

The capacity loss due to anode overcharging is mainly due to the generation of electrochemically inert substances (e.g., Co3O4, Mn2O3, etc.), which disrupts the capacity balance between the electrodes, and the capacity loss is irreversible. Even the excessive amount of lithium removal can cause structural collapse. For conventional lithium cobaltate, ternary, the maximum amount of lithium removal is about 50%; for the more stable structure of olivine type lithium iron phosphate, the maximum amount of lithium removal is about 80%.

① LiyCoO2

LiyCoO2→(1-y)/3[Co3O4 + O2(g)]+yLiCoO2 y<0.4

At the same time, the oxygen produced by the decomposition of cathode materials in a sealed lithium-ion battery due to the absence of recombination reactions (e.g., to generate H2O) and the simultaneous accumulation of flammable gases produced by the decomposition of the electrolyte, the consequences will be unimaginable.

② λ-MnO2

lithium manganese reaction occurs in the state of lithium manganese oxide completely de-lithium: λ-MnO2→Mn2O3+O2(g)

3. the electrolyte oxidation reaction in the overcharge

When the pressure is higher than 4.5V, the electrolyte will oxidize and generate insoluble substances (such as Li2Co3) and gas. These insoluble substances will clog the pores of the electrode and impede the migration of lithium ions, resulting in the loss of capacity during the cycle. Factors affecting the oxidation rate:

• the surface area of the anode material
• the collector material
• the added conductive agent (carbon black, etc.)
• Types of carbon black and surface area size

Of the more commonly used electrolytes today, EC/DMC is considered to have the highest oxidation resistance. The electrochemical oxidation process of a solution is generally expressed as: solution → oxidation products (gases, solutions, and solid substances) + ne – The oxidation of any solvent will increase the electrolyte concentration and decrease the stability of the electrolyte, ultimately affecting the capacity of the battery. The reaction is more complicated when overcharging occurs in the whole battery. Take the 40Ah NCM111+LMO/Gr battery as an example, the changes in voltage, temperature, and internal resistance during the overcharging process are shown in Figure 2, which can be roughly divided into four stages.

• Stage 1: 1<SOC<1.2, no significant side reactions occur within the cell, with small changes in cell temperature and internal resistance.
• Stage 2: 1.2<SOC<1.4, Mn in the positive electrode is dissolved, the electrolyte is oxidized on the positive side, and lithium metal is precipitated on the negative surface. The reaction between lithium metal and solvent makes the SEI film thicker, the cell impedance increases, and the cell temperature starts to rise slowly.
• Stage 3: 1.4<SOC<1.6, the battery temperature rises faster, the battery bulges significantly, and the oxidation of electrolyte on the positive side accelerates, releasing a large amount of heat and gas. The lithium metal on the cathode surface continues to precipitate, the SEI film begins to decompose, and the lithiated graphite reacts with the electrolyte. Due to the change in the structure of the cathode material, the battery voltage reaches a peak of 5.2V and then drops slightly.
• Stage 4: SOC>1.6, the internal pressure of the battery exceeds the limit, the shell breaks down, the diaphragm shrinks and deforms, and the battery thermal runaway. A short circuit occurs inside the battery, a large amount of energy is released rapidly, and the battery temperature rises sharply to 780℃. The side reactions in each stage of overcharging are shown in Figure 3.

Fig. 5 Voltage, internal resistance, and temperature changes during the overcharging of NCM+LMO/Gr battery.

Figure 6: Schematic diagram of the reaction mechanism in the overcharge stage

References: D.Ren et al. / Journal of Power Sources.

The walk-in test chamber is specifically designed to perform temperature and humidity testing on products and materials to ensure it meets the certified safety and performance requirements. The walk-in test chamber is designed in different sizes along with necessary features that are necessary for testing heat, cooling, humidity endurance of your development for safety and performance. The walk-in test chamber comes in different sizes, from the small chamber that can fit on top of a table to the large room size testing chambers.

However, the benchtop test chamber (also called the small environmental chamber) is quite different from the walk-in test chamber based on its appearance and features. The benchtop test chambers are very suitable for performing both humidity and temperature tests on products and materials to ensure adequate performance and safety. Both the walk-in test chamber and benchtop test chambers serve the same purpose, which is the testing of products and materials capabilities by subjecting it to different temperature conditions for a thorough evaluation. The benchtop test chambers are very portable and small in size, making it easy to perform tests on a small amount of space. As the name sounds, the benchtop test chamber can easily fit on top of a bench or table.

What are the walk-in test chamber and benchtop test chamber used for?

The walk-in test chamber type of temperature and humidity chamber is designed for testing the capability of heat, cold, dryness, and humidity of products and materials. The walk-in test chamber comes with quality features and controls that are suitable to test products effectively under any condition. The walk-in test chamber comes in different varieties of sizes, which makes it suitable for testing large and small objects. For the large room walk-in test chambers, products and materials can also be tested in batches simultaneously, being beneficial to manufacturing industries. The walk-in test chamber can simulate temperature during the testing process ranging from -60°C to 90°C, which can vary depending on the machine features.

Testing products with the walk-in test chamber is similar to the benchtop test chamber when it comes to machine testing features. However, for the products and materials, the benchtop test chambers are not suitable for large product testing.

Type of tests performed in the walk-in test chamber and benchtop test chamber

walk-in test chambers are used in performing testing on products that require large testing chambers. For small products, it can be subjected to batch testing inside the walk-in test chamber. The benchtop test chamber is suitable for testing small products due to its portability and small design size. However, when it comes to the type of test that both walk-in test chamber and benchtop test chamber can perform, it includes:

• Storage test
• Altitude test
• Vibration test
• Temperature and humidity tests
• Salt spray and salt forge testing
• etc

walk-in test chambers serve the need of performing climatic tests on complex and huge equipment that will be hard to test other test machines. Walk-in test chamber and benchtop test chambers come with high-level technology that is efficient in boosting the testing process of products.

The features of the Walk-in test chamber and benchtop test chamber

Both the walk-in test chambers and benchtop test chamber stimulates different climates and environments for evaluating product safety and quality. The walk-in test chambers and benchtop test chamber comes with efficient technological components that are superior for conducting temperature and relative humidity product tests.

Features of the walk-in test chamber and benchtop test chamber include:

• Chamber is equipped with doors and windows with extensive heat insulation for observation, which size may vary depending on the test chamber size.
• LED, LCD, or RH display along with sensors for touch commands.
• The chamber contains air compressors and condensers for controlling the temperature inside the system.
• USB, Ethernet, Bluetooth, and Wifi for sending files and commands to the system. Not all test chamber comes with these features.
• Remote controller for receiving commands.
• Chamber compartment with racks and shelves for keeping specimens stable.
• Access plugs and ports for connections, etc.

The above features of the walk-in test chamber and benchtop test chambers determine the machine capabilities, according to temperature and relative humidity during the testing process. There’s not much difference in terms of features between the walk-in test chamber and benchtop test chamber because as technology advancement continues, each test machine comes with different features, which makes it suitable for performing tests.

Choosing between the walk-in test chamber and benchtop test chamber

Determining the type of machine suitable for each product testing is based on the size and features of the testing chamber. Based on the products to be tested, thorough research and evaluation of different test chambers are necessary when choosing between the walk-in test chamber and benchtop test chamber.

In most cases, for testing large-size products, it’s recommended to make use of the walk-in test chamber because of its ability to accommodate big products and materials such as refrigerators, cars, etc.  Therefore, determining the size of products or materials that will be tested on the test chamber is necessary when choosing between a walk-in test chamber and a benchtop test chamber. For manufacturing industries that produce products and materials of different sizes, it’s necessary to choose a test chamber that can accommodate the testing of large and small size objects like the walk-in test chambers.

The benchtop test chamber is durable and efficient when testing small size products or specimens at the initial stage of development accurately. Therefore, before making the final choice of choosing between the walk-in test chamber and benchtop test chamber, it’s necessary to take the time of evaluating the testing features and the storage needs of your product or material, which includes:

1. The construction material of the chamber will determine whether it’s suitable for high-temperature applications. It’s relative humidity range, which can vary in test chambers.
2. External and internal features of the test chamber, such as air compressors and condensers for lowering and increasing temperatures when needed. Power of the test machine in the heating and cooling of the chamber system during the testing process.
3. Choose chamber with trending features and latest technological upgrade that includes touch LCD or LED, RH displays, sensors, etc.
4. Ensure that the chamber has wielded walls and fitted doors with gaskets that will prevent leakage when testing products. Check whether the test chamber is fitted with a perfect filter exhaust for removing harmful airs or gases when performing tests.