The temperature humidity test chamber indicates the effect of temperature changes on materials and products. The temperature humidity test chamber aids effectively in ensuring positive outcomes in products with strict limits to failures.

The humidity test chambers are developed in different sizes with a series of innovative features from brands like DGBell’s temperature humidity test chamber. Most temperature humidity test chambers are small in size for testing smaller products and materials, while the larger machines are for testing bigger products.

However, when it comes to choosing of temperature humidity test chamber, there are several things to consider, which includes:

• Humidity range

The normal relative humidity range of environmental test machines range from 20% RH ~ 98% RH. Considering the humidity range when choosing a humidity test chamber is necessary as most chambers have certain humidity indicators. It’s this indicator from the chamber that indicates the type of test supported by the machine. Most humidity test chambers are perfect in getting results for high wet tests, while some are used for low tests.

• Temperature range

Another important thing to worry about is the temperature range which often ranges from  -70 ~ 150°C. This can be determined based on the temperature of the products or material that will be tested on the humidity chamber.

• Performance

Researching and comparing series of humidity test chambers along with its ascertain features is important. During this period, choosing the machine with highly improved performance should be the goal. The performance stats of any environmental test machine is what determines its positivity and accuracy output when testing products and material.

• Cost

The selection of appropriate environmental test machines is always complex because the cost is among the first things to consider. The humidity test machine varies with each other in terms of efficiency, performance, and features that aids in creating different price rates. Therefore, depending on your budget and the need you have for getting a humidity test machine, the evaluation of machine costs based on the features required is necessary.

• Machine control method

The machine control methods for humidity test chambers are divided into two including the constant test chamber and alternating chamber, which is different from each other. Therefore the selection of the humidity test machine depends on the user’s needs along with the type of test machine they can control.

• Temperature changes

In most chambers, environmental test temperature always changes, making it easy when assigning parameters. Although certain test chambers like the DGBell’s temperature humidity test chamber give users the ability to control the test machine effectively by a certain parameter.

• Volume evaluation

Considering the volume available for testing products and materials Is necessary when choosing a humidity test chamber. As indicated earlier that most humidity test machines are big while some are small. The same fact applies to the amount of test volume a machine might accommodate. Therefore evaluating the products or material to be tested on the machine gives the user the ability to get an extended chamber with accurate volume.

Moreover, the last thing to consider is the cooling method which includes the air and water cooling methods. The choice of the cooling method of the machine should be based on the situation of the environment. Although in most cases users prefer making use of the water-cooled version of the temperature humidity test chamber, as it’s friendly with most conditions.

What are the main aspects of secondary battery performance?

Voltage, internal resistance, capacity, internal pressure, self-discharge rate, cycle life, sealing performance, safety performance, storage performance, appearance, etc., others are overcharge, over-discharge, solderability, corrosion resistance, etc.

What are the electrical performance indicators of mobile phone battery blocks?

There are many electrical performance indexes of the battery block. Only the main electrical characteristics are introduced here:

• Battery block capacity: This indicator reflects the amount of electrical energy that the battery block can store in milliampere hours, for example, 1600mAH means that the battery can be continuously discharged for one hour at 1600mA.
• Battery block life: This indicator reflects the number of repeated charge and discharge cycles of the battery block.
• The internal resistance of the battery block: the smaller the internal resistance of the battery block, the better, but it cannot be zero.
• Battery block charging upper limit protection performance: When charging a lithium battery, the upper limit of its voltage has a rating. In any case, the voltage of the lithium battery is not allowed to exceed this rating. It is determined and guaranteed by the IC selected on the PCB.
• Battery block discharge lower limit protection performance: When the lithium battery block is discharged, the voltage of the lithium battery is not allowed to be lower than a certain rating under any circumstances. The rating is determined and guaranteed by the IC selected on the PCB. It should be noted that, when the general lithium battery block in the mobile phone is discharged, the lower limit protection value has not been reached, and the mobile phone is shut down due to insufficient battery power.
• Battery block short-circuits protection characteristics: When the exposed positive and negative plates of the lithium battery block are short-circuited, the IC on the PCB board should be immediately judged and reacted to turn off the MOSFET. When the short-circuit fault is eliminated, the battery can immediately output electrical energy. These are identified and executed by the IC on the PCB.

What are the battery reliability test items?

Generally includes:

1. Cycle life
2. Different rate discharge characteristics
3. Different temperature discharge characteristics
4. Charging characteristics
5. Self-discharge characteristics
6. Different temperature self-discharge characteristics
7. Storage characteristics
8. Over-discharge characteristics
9. Internal resistance characteristics at different temperatures
10. High temperature test
11. Temperature cycle test
12. Drop test
13. Vibration test
14. Capacity distribution test
15. Internal resistance distribution test
16. Static discharge test ESD.

What are the battery safety test items?

Generally includes:

1. 1.Internal short circuit test
2. Continuous charging test
3. Overcharge
4. High current charging
5. Forced discharge
6. Drop test
7. Drop test from a height
8. Penetration test
9. Plane crushing test
10. Cutting experiment
11. Shelf test in low pressure
12. Thermal abuse experiment
13. Water immersion experiment
14. Burning experiment
15. High pressure experiment
16. Baking experiment
17. Electronic furnace experiment.

The mobile phone lithium battery is a finished battery composed of battery cell and battery protection board. The mobile phone lithium battery will be activated before leaving the factory. After a series of processes of filling the battery case with electrolyte-sealing-forming-dividing, the activation of the mobile phone lithium battery is completed.

The activated mobile phone lithium battery also needs to be functionally tested. The purpose of the test is to verify whether the battery quality is qualified and to prevent the circulation of inferior batteries from the source. The mobile phone lithium battery test mainly uses power, switches, electronic loads, multimeters, and other instruments to test the battery’s over-current and over-voltage, and checks whether the battery protection board can react quickly to protect the battery.In this process, we also need to use the battery test module – high current shrapnel microneedle module, which is mainly used for conducting current and transmitting signals.

Mobile phone lithium battery testing is mainly carried out for functions such as functionality, safety, and reliability, because lithium batteries are prone to heat, expansion and even explosion due to overcharge, over-discharge, short circuit, and other reasons, so they must be tested to confirm whether it can be applied.

The purpose of a mobile phone lithium battery functional test

To test whether the function of the battery can be achieved. The test content: high and low temperature charge and discharge, charge retention capacity, battery rate, capacity, life cycle, etc.

The purpose of a mobile phone lithium battery safety test

To test whether the battery protection board can cut off the current loop in time when the battery has abnormal conditions to avoid the occurrence of dangerous accidents. Test content: overcharge, over-discharge, abnormal charge, forced discharge, external short circuit, power limit detection, etc.

The purpose of a mobile lithium battery reliability test

To test whether the battery can work normally in different external environments. Test content: low pressure, vibration, impact, crush, free drop, impact, temperature change, shell stress, etc.

The mobile phone lithium battery test must ensure the stability of the current flow. As a battery test module, the high current spring micro pin module has good current transmission ability and can carry out current transmission in the range of 1-50a, and the over-current is stable and smooth, with no current attenuation. In the small pitch field, it can adapt to the pitch value between 0.15mm-0.4mm. It has excellent service life and stability, can maintain a good connection, and won’t be stuck with a PIN or broken needle.

In addition to battery quality, cell phone lithium battery testing must also consider how to increase battery output, reduce production costs, and maximize benefits. Under the high-frequency test, the average service life of the high current shrapnel microneedle module can reach more than 20w times. If the operation, environment, and maintenance are good, the service life can reach 50w times, and the shrapnel head has a self-cleaning design, which can maximize the use, and greatly improve the testing efficiency of mobile phone lithium batteries.

In addition, the high-current shrapnel microneedle module has a short delivery time and high yield, which can maintain long-term stability in the mobile phone lithium battery test. It is a battery test module with absolute advantages and ultra-high adaptability.

Lithium battery, I think we should be more rigorous. It should be called the lithium-ion secondary battery. Li is the smallest diameter and most active metal on the element periodic table. If you are not sure, you can look at the periodic table “Lithium hydrogen-helium beryllium boron, carbon-nitrogen, oxygen, fluorine, and neon…”. Because Li has these characteristics, it is widely favored by smart scientists and engineers.

However, this is also a double-edged sword. When lithium metal is exposed to the air, it will violently oxidize with the oxygen in the air and explode. This is also a difficult problem in pre lithium. So in the daily electrode materials, we usually use alloy materials and graphite to store lithium atoms. These materials are like a small storage grid. The lithium atoms lie in it, and the larger oxygen molecules cannot enter. Their reaction will not happen, avoid explosions, and thus achieve safety purposes.

When a lithium-ion battery is charged, the lithium atoms in the positive electrode will lose electrons and oxidize to lithium ions. Lithium ions to the negative electrode through the electrolyte, enter the layer structure of the negative electrode and obtain an electron, which is reduced to lithium atoms. When discharging, the whole procedure is reversed. (This is the origin of the rocking chair battery. The rocking chair battery refers to the charging and discharging process of the lithium-ion battery, which is the intercalation and deintercalation process of lithium ions. During the intercalation and deintercalation of lithium ions, it is accompanied by the equivalent of lithium ions. Intercalation and deintercalation of electrons. In the process of charging and discharging, lithium ions are intercalated / deintercalated and intercalated / deintercalated between the positive and negative electrodes). To prevent the short circuit caused by the direct contact between the positive and negative electrodes of the battery, a diaphragm with many pores is added in the battery to prevent short circuits. A good diaphragm can also automatically close the pores when the battery temperature is too high so that lithium ions can not pass through to prevent danger.

Lithium-ion battery common causes of the explosion

1. There are serious quality problems with raw materials and incoming materials, mainly the quality of the electrolyte;
2. The electrode piece absorbs water, and the water reacts with the electrolyte to generate a large amount of gas and heat;
3. The results show that the charge-discharge internal resistance is larger due to the less liquid injection, which affects lithium-ion transmission;
4. The welding and sealing procedures of the cover are poor, the sealing performance is poor, there is air leakage, and the external moisture enters;
5. The internal micro short circuit is mainly dust burr, which is mainly caused by the electrode plate cutting off and cutter burr;
6. When the current is too high, the negative electrode can not accept more lithium ions, forming dendrite, piercing the diaphragm and short circuit;
7. The battery is overcharged, the material structure collapses, and lithium dendrites form a piercing membrane.

Lithium-ion battery explosion type analysis

The explosion types of lithium-ion batteries are mainly divided into short circuit and overcharge, and short circuit is divided into an internal short circuit and external short circuit.

Let’s talk about the external short circuit first. The principle is very simple. A conductive substance connects the positive and negative electrodes simultaneously from the outside of the battery. When an external short circuit occurs, the current increases and the battery begins to generate heat. When the heat becomes larger, the electrolyte will decompose, generating a large amount of gas, and the battery will swell.

We said that many diaphragms have the function of closing the pores. At a certain temperature, the diaphragms will close the pores and prevent the transmission of lithium ions, thereby blocking the chemical reaction. The current drops and the temperature also drop slowly, thus avoiding the battery explosion. Of course, the above is only based on the good quality diaphragm.

The internal short circuit is mainly caused by the burrs of copper foil and aluminum foil piercing the diaphragm, or the dendrite crystal of lithium atoms piercing the diaphragm. These tiny needle-shaped metals can cause micro short circuits. Because it is very thin and has a certain resistance value, the current may not be very large. Burrs of copper and aluminum foil can be caused in the production process. The phenomena that can be observed are battery leakage and fast self-discharge. Most of them can be detected by short-circuiting testers. Moreover, due to the small burr, it is sometimes burned out, making the battery return to normal. Therefore, the probability of an explosion caused by the micro short circuit of burr is not high. Burr mainly comes from slitting, laser cutting has few burrs.

There are more sources of dendrites (when the liquid metal solidifies, the solid crystal nucleus grows faster along with certain crystal directions, resulting in the formation of dendritic crystals, referred to as dendrites. The general dendrite size is very small, the length is a few millimeters. The crystal is composed of tens of thousands or millions of crystal grains. The crystal grains in a dendrite have a similar orientation. The serious dendrite structure has an adverse effect on the thermoplasticity), high current, lithium precipitation, etc. will cause.

The explosion caused by overcharge is relatively common. After overcharge, there are needle-like lithium crystals on the electrode plate, puncture points are everywhere, and the micro short circuit occurs everywhere. Therefore, the battery temperature will gradually increase, and finally, the high temperature will change the electrolyte gas. In this case, whether the temperature is too high to make the material burn and explode, or the shell is broken first, which makes the air in and oxidizes the lithium metal violently, all are explosions. However, the explosion caused by the internal short circuit caused by overcharge does not necessarily occur at the time of charging.

According to the analysis of commonly mobile phone batteries, there is still a case, when the battery temperature is not high enough to burn the material, and the gas generated is not enough to break through the battery casing. We then terminate charging and take the mobile phone out.

At this time, the heat generated by many micro-shorts gradually raises the temperature of the battery. After a period of time, the explosion occurs. The common description of consumers is that when the phone is picked up, the phone is very hot, and it explodes after being thrown away. Although now have an automatic power-off function, but still a warm reminder, try not to charge for a long time.

Lithium-ion battery protection mechanism

Whether it is charging or discharging, we have a measure, usually using voltage to stop. Taking the ternary battery with lithium nickel cobalt manganese oxide and graphite anode as an example. When the battery charging voltage is higher than 4.2V, the danger will come quietly. The higher the voltage, the higher the danger. Because when the voltage is higher than 4.2V, the number of lithium atoms in the positive electrode material decreases, the structure of the stored atoms will collapse, which is permanent and irreversible.

If you continue to charge, the lithium-ion will generate lithium metal with electrons on the surface of the negative electrode, which is called dendrites. These dendrites will pierce the separator and short-circuit the positive and negative electrodes.

Overcharging will also increase the temperature. If the temperature exceeds 180°C, the electrolyte will decompose and generate a large amount of gas and heat. The shell will expand. After the rupture, oxygen enters and reacts violently with lithium metal and will explode. Therefore, the upper limit of the charging voltage is a protective measure.

The last line of defense for lithium-ion battery

Usually, our batteries, whether it is a mobile phone or a power battery, have a battery management system (or software) and a battery protection circuit board to monitor the battery voltage during battery charging and discharging to prevent overcharging, over-discharge, large

Current generation. If none of the above can protect the battery and avoid the explosion, it is only possible to reduce the damage through self-destruction. These need to be provided by the battery cell, such as the explosion-proof valve of the battery, anti-overcharge Fuse with SSD flip-flop, cut off the current, and pressure relief to reduce the risk of a battery explosion.

DGBell has special test chambers to deal with the overcharge and over-discharge of the battery and the occurrence of short circuits. We have been focusing on the safety test of the battery.