Detailed explanation of lithium-ion battery overcharge, over-discharge, short circuit protection circuit

　　Author ：Iflowpower – Portable Power Station Supplier

Lithium-ion battery base lithium-ion battery is a rechargeable battery, and the general lithium ion battery is fully charged that there is also a battery that has other voltages. Lithium-ion battery capacity is xxxmah, such as 1000mAh, 1000mA power supply current can be used for 1 hour. 500mA power supply 2 hours.

So on and so forth. Life and charging method of lithium-ion batteries refers to the number of times the full charge. Charging method: fast charge, slow charge, trickle charging, constant current charging, etc.

Lithium-ion battery circuit design attention problem: lithium-ion battery overger, over-discharge can affect battery life. Pay attention to the charging voltage of lithium ion batteries, charging current. Then select the appropriate charging chip.

Note that there should be problems such as overchard, over, short circuit protection of lithium-ion batteries. After the design, you should have a lot of testing. The design of the lithium-ion battery charging circuit is selected for the chip TP4056 as an example.

Control the maximum current according to the received resistance. You can design a charging indicator, which can design the charging temperature, how much is more to charge. The charging protection circuit, the combination of choices of chips DW01 and GTT8205 can be short-circuited, and the protection of over charged discharge.

The circuit is important from the lithium ion battery protection special integrated circuit DW01, charge, and discharge control MOSFET1 (including two N-channel MOSFETs), etc., the monomer lithium ion battery is connected between B + and B-, the battery pack is from P + And P-output voltage. When charging, the charger output voltage is connected between P + and P-, current from the B + and B- B- of the P + to the monomer battery, and then charge the MOSFET to P-.

During the charging process, when the voltage of the monomer battery exceeds 4.35V, the OC foot output signal of the dedicated integrated circuit DW01 causes the charging control MOSFET to shut down, and the lithium ion battery immediately stops charging, preventing the lithium ion battery from being damaged by overcharging. During the discharge process, when the voltage of the monomer battery drops to 2.

30 V, the OD pin output signal of DW01 causes the discharge control MOSFET, and the lithium ion battery immediately stops discharge, thereby preventing the lithium ion battery from being damaged by over-discharge, DW01 CS The foot is current detection feet, when the output is short, the turning and discharge control MOSFET has increased, the CS foot voltage rapidly, the DW01 output signal enables the charge and discharge control MOSFET to shut down, thereby achieving overcurrent or short circuit protection. What is the advantage of lithium ion batteries? 1. High energy density 2.

High operating voltage 3. No memory effect 4. Circulation life 5.

No pollution 6. Weight light 7. Self-discharge small lithium polymer battery 1.

No battery leakage problem, the internal battery does not contain liquid electrolyte, using colloidal solid. 2. Make a thin battery: with a capacity of 3.

6V400mAh, its thickness can be thin to 0.5mm. 3.

The battery can be designed to be a variety of shapes 4. Battery can be bendable: the polymer battery maximum can bend 900 or so 5. Can be made into a single high voltage: the battery of the liquid electrolyte can only be connected in series with several batteries, high voltage, high The molecular battery can achieve a high voltage due to liquid bodies in its own.

7. Capacity will be doubled than the same size of lithium ion batteries. IEC specifies that the lithium ion battery standard cycle life test is: the battery is placed in 0.

2c to 3.0V / branch 1.1C constant current constant pressure charge to 4.

2V deadline 20mA The shelving is 1 hour and then discharged from 0.2c to 3.0V (a loop) Repeated cycle 500 after the capacity should be more than 60% of the primary capacity.

Standard charge-removal test of the lithium-ion battery (IEC does not have relevant standards). Battery After the 25 degrees Celsius is placed in 0.2c to 3.

0 / branch, the constant current constant pressure charged to 4.2V, the cutoff current is 10mA, and after 28 days of temperature is 20 + _5, it is discharged to 2.75V calculation by 0.

2C. Discharge capacity What is the self-discipline of different types of secondary batteries Different types of self-discharge ratio? Self-discharge is also known to charge capacity, it refers to the capacity of battery storage under certain environmental conditions in a certain environmental basis. In general, self-discharging is important for manufacturing processes, materials, storage conditions, self-discharge is one of the important parameters of measurement of battery performance.

In general, the lower the battery storage temperature, the lower the self-discharge rate, but it should also note that the temperature is too low or too high, which may cause the battery damage. BYD regular battery requires storage temperature range to -20 ~ 45. After the battery is filled with electricity, it is a certain degree of self-discharge.

The IEC standard specifies that the nickel-cadmium and nickel-hydrogen battery are filled with electricity, and the opening is on standing for 28 days, and 0.2c discharge time is greater than 3 hours and 3 hours, 15 points. Compared with other charging battery systems, the self-discharge ratio of the liquid electrolyte solar cell is significantly low, approximately 10% under 25 / month.

What is the internal resistance of the battery? The internal resistance of the battery refers to the resistance from the battery at operation, which is generally divided into the internal resistance and DC internal resistance. Since the internal resistance of the charging battery is small. Due to the internal resistance of the stream, due to the electrode capacity polarization, the polarized internal resistance is displayed, and its true value cannot be measured, and the effect of its AC internal resistance is exempted from polarized internal resistance, and the real internal value is obtained.

The test method is: utilizing a battery equivalent to an active resistance, a series of processing such as 1000Hz, 50 mA, and a series of processing such as voltage sampling rectifier filtering, etc., to accurately measure the resistance value. What is battery internal pressure? How much is the battery normal internal pressure? The internal pressure of the battery is due to the pressure formed by the gas that occurs during the charge and discharge process.

Important is affected by the factors of battery material manufacturing processes, structures, etc. Generally, the internal pressure is maintained at normal levels. In the case of overcharge or overlapping, the internal pressure may rise: if the speed of the composite reaction is lower than the speed of the decomposition reaction, the gas that occurs is not required to be consumed, resulting in high pressure in the battery.

What is Pressure test? Lithium ion battery internal pressure test is: (UL standard) The analog battery is under high altitude (low air pressure 11.6kpa) at sea level (low air pressure 11.6kpa), check whether the battery is leakage or drum.

Details: charge the battery 1C constant current Constant voltage is charged to 4.2V, the cutoff is 10mA, and then placed in a low pressure box of 11.6 kPa, the temperature is (20 + _3), and the battery does not explode, fire, crack, leakage.

Ambient temperature What is the impact on battery performance? In all environmental factors, the temperature on the battery's charge and discharge performance is the largest, and the electrochemical reaction on the electrode / electrolyte interface is related to the ambient temperature, the electrode / electrolyte interface is considered a battery. heart. If the temperature decreases, the reaction rate of the electrode also decreases, assuming that the battery voltage is kept constant, the discharge current is lowered, and the power output of the battery will also fall.

If the temperature rises, that is, the battery output power will rise, the temperature also affects the temperature of the transmission speed of the electrolyte, speeds up, the transfer temperature is lowered, the transmission is slow, and the battery charge and discharge performance will also be affected. However, the temperature is too high, more than 45, which will damage the chemical balance in the battery, resulting in a control method for the sub-reactance overcharge, to prevent the battery excessive charge, to control the charging endpoint, there will be some special Information availability to determine if the charging reaches the end. There are generally the following six ways to prevent the battery from being overchaled: 1.

Peak voltage control: Judgment the end of charging by detecting the peak voltage of the battery; 2. DT / DT control: Judgment the end of charging by detecting the peak temperature change rate of the battery ; 3.T control: The difference between the battery is full of electricity and the ambient temperature will be maximized; 4.

-V Control: After the battery is charged to a peak voltage, the voltage will drop a certain value 5. Time control: By setting certain The charging time controls the charging end point, which is generally set to charge the time required to charge 130% nominal capacity; 6.TCO control: Considering the safety and characteristics of the battery should prevent high temperature (except high temperature battery), so when the battery When the temperature is increased 60, the charging should be stopped.

What is overchaout, what is the impact on battery performance? Over-rechargeing means that the battery is fully charged, then continues to charge. Since the negative electrode capacity is higher than the positive electrode capacity, the gas generated by the positive electrode transmits the cadmium compression of the diaphragm paper and the negative electrode. Therefore, in general, the internal pressure of the battery will not be significantly increased, but if the charging current is too large, the charging time is too long, the oxygen that occurs is too late to consume, which may cause the internal pressure rise, the battery deformation, and the leakage.

Waiting for bad phenomena. At the same time, its electrical performance will also be significantly reduced. What is over-discharge? What is influenced on the battery performance? After the battery is placed, the voltage reaches a certain value, and the discharge will result in an over-discharge, which is usually determined according to the discharge current to determine the discharge cutoff voltage.

0.2C-2C discharge is typically set 1.0V / branch, 3C or more, and the discharge of 5C or 10C is set to 0.

8V / branch, battery excess may bring catastrophic consequences to the battery, especially large current over, or Repeated overlapping the battery effect is greater. In general, the over-discharge will increase the internal pressure of the battery, and the positive and negative active substance is reversible, even if charging can only be partially recovered, the capacity will also be significantly attenuated. What is the problem with the battery combination of different capacity? If you use different capacities or new-term batteries, it is possible to show the phenomenon of leakage, zero voltage.

This is due to the charging process, and some batteries are overcharged during charging. Some batteries are not filled with electricity, and the battery has high capacity is not filled, and the capacity is low. Such a vicious circle, the battery is damaged and the liquid or low (zero) voltage.

What is the explosion of the battery to prevent battery explosion? The solid matter in the battery is instantly discharged, and it is pushed to a distance from 25 cm above the battery, called an explosion. Detailed battery explosion or not, using the following conditions. Hand in the experimental battery, the battery is in the middle, and the net cover is 25cm.

The network has a density of 6-7 roots / cm. The network cable uses a soft aluminum wire having a diameter of 0.25 mm.

If the experimental free solid portion passes the net cover, the battery has not exploded. The problem of tandem of lithium ion battery Since the battery is starting from the coating film to become a finished product, it is necessary to pass many steps. Even with rigorous detection procedures, the voltage, resistance, capacity of each set of power is consistent, but it will also appear like this or such differences.

Like a twin of a mother, it may grow exactly when it is just now, and it is difficult to distinguish it as a mother. However, when two children grow up, there will be such or such differences in lithium batteries. After using a difference in a period of time, the way the overall voltage control is used is difficult to apply to a lithium power lithium battery, such as a 36V battery heap, and must be connected in series with 10 batteries.

The overall charging control voltage is 42V, and the discharge control voltage is 26V. With an overall voltage control method, the initial use phase is particularly good because the battery consistency is particularly good. Maybe there is no problem.

After using a period of time, the battery internal resistance and voltage fluctuate, form an inconsistent state, (inconsistent is absolute, the consistency is relative) This time it is still using the overall voltage control without achieving its purpose. For example, the voltage of the two batteries at 2.8V, the voltage of the four batteries is 3.

2V, and now the overall voltage is 32V, and we let it continue to discharge it all the time to work 26V. In this way, the two 2.8V batteries are below 2.

6V. The lithium-ion battery has been equal to the scrap. Conversely, charging is carried out in a manner of controlling charging, and there will be a state of excessive conditions.

For example, charging the voltage state at the time of the above 10 batteries. When the overall voltage reaches 42V, the two 2.8V batteries are hungry, while rapid absorption of electricity, will exceed 4.

2V, and overcharged more than 4.2V batteries, not only due to high voltage, but also In danger, this is the characteristics of lithium powered lithium batteries. The rated voltage of the lithium ion battery is 3.

6V (some products are 3.7V). The termination charging voltage is related to the electricity of the battery is related to the battery anode material: the anode material is 4.

2V of graphite; the anode material is 4.1V of coke. The internal resistance of different anode materials is also different, and the internal resistance of the coke anode is high, and its discharge curve is also slightly different, as shown in Figure 1.

Generally referred to as 4.1V lithium ion battery and 4.2V lithium ion battery.

Most of the use of 4.2V, the termination discharge voltage of the lithium-ion battery is 2.5V ~ 2.

75V (the battery plant gives the operating voltage range or gives the termination discharge voltage, each parameter is slightly different). It is below the termination of the discharge voltage to continue to discharge, and the battery will damage the battery. Portable electronic products are powered as a battery.

With the rapid development of portable products, the amount of various batteries has increased, and many new batteries have been developed. In addition to the high-performance alkaline batteries that you are more familiar with, it is rechargeable nickel-cadmium batteries, and there are lithium-ion batteries developed in recent years. This article is important to introduce basic knowledge about lithium-ion batteries.

This includes its characteristics, important parameters, model, application range and precautions, etc. Lithium is a metal element, which is Li (its English name lithium). It is a silver white, very soft, chemically lively metal, the lightest in metal.

In addition to being applied to atomic energy industry, it can make special alloys, special glass (fluorescent screen glass on television) and lithium-ion batteries. In the lithium ion battery used as the anode of the battery. Lithium-ion batteries are also divided into two categories: two categories that are not chargeable and rechargeable.

The non-rechargeable battery is called a disposable battery, which can only convert chemical energy to electrical energy, and cannot reduce the electrical energy reduction to chemical energy (or the reduction performance is extremely poor). The rechargeable battery is called a secondary battery (also known as a battery). It can convert power into chemical energy, when used, then convert chemical energy into electrical energy, it is reversible, such as an important feature of electrochemical lithium ion battery.

The smart portable electronic product requires light size, but the size and weight of the battery are often the greatest and most important than other electronic components. For example, the big brother who wants the year is quite thick, cumbersome, and today's mobile phone is so light. Among them, the battery improvement is an important purpose: the past is a nickel-cadmium battery, and now is a lithium-ion battery.

The greatest feature of lithium-ion batteries is higher than energy. What is more energy? The energy refers to energy is the energy of the unit weight or unit volume. Represents WH / KG or WH / L for energy.

The unit is the unit of energy, W is the watt, H is hour; kg is a kilogram (weight unit), L is liter (volume unit). Here, an example is to explain that the rated voltage of the No. 5 nickel-cadmium battery is 12V, its capacity is 800mAh, and its energy is 096Wh (12V×08ah).

The same size 5 lithium -canium dioxide battery has a rated voltage of 3V, which has a capacity of 1200mAh, and its energy is 36Wh. The volume of these two batteries is the same, then the ratio energy of the lithium-manganese dioxide battery is 375 times the nickel-cadmium battery! The 5-nickel-cadmium battery is about 23g, and one 5 lithium-manganese dioxide battery Dazhong 18g. One lithium-manganese dioxide battery is 3V, while two nickel-cadmium batteries are only 24V.

Therefore, the number of batteries in the battery when using a lithium-ion battery (alleviating the portable electronic product volume reduces piety weight), and the battery is working. In addition, the lithium-ion battery has the advantages of stable discharge voltage, wide operating temperature range, low self-discharge rate, long storage life, no memory effect and pollution-free. Unchargeable lithium-ion batteries are not rechargeable lithium ion batteries, currently commonly used lithium-manganese dioxide batteries, lithium thionyl chloride batteries and lithium and other compound batteries.

This article only introduces the top two most commonly used. 1, lithium-manganese dioxide battery (LIMNO2) lithium-manganese dioxide battery is a disposable battery based on lithium as an anode, manganese dioxide as a cathode, and using an organic electrolyte liquid. The important feature of the battery is that the battery voltage is high, the rated voltage is 3V (which is 2 times the general alkaline battery); the termination discharge voltage is 2V; the amount is larger than the energy (see the example above); the discharge voltage is stable and reliable; Storage performance (more than 3 years), low discharge rate (annual self-discharge rate 2%); operating temperature range -20 ¡ã C ~ + 60 ¡ã C.

The battery can be made into different shapes to meet different requirements, it has rectangular, cylindrical and buttons (buckles). Cylindrical also has different diameters and high dimensions. Here is an important parameter of 1 # (size code D), 2 # (size code C), and 5 # (size code AA) battery that is more familiar with.

Cr is represented as a cylindrical lithium-manganese dioxide battery; in the five digits, the first two digits represent the diameter of the battery, and the last three indicates the height of a decimal. For example, CR14505 has a diameter of 14 mm and a height of 505 mm (this model is universal). Here, it is pointed out that the parameters of the same model produced by different plants may have some differences.

Further, the standard discharge current value is small, and the actual discharge current can be greater than the standard discharge current, and the allowable discharge current of continuous discharge and pulse discharge is also different, and the data is supplied by the battery factory. For example, the CR14505 produced by Li Qixi power company gives the maximum continuous discharge current of 1000mA, and the maximum pulse discharge current can reach 2500mA. Most of the lithium ion batteries used in the camera are lithium-manganese dioxide batteries.

Here, the lithium-manganese dioxide cells commonly used in the camera are included in Table 2 for reference. The button (button) battery is small, its diameter is 125 ~ 245mm, height is 16 ~ 50mm. Several more common buckles are shown in Table 3.

Cr is a cylindrical lithium-manganese dioxide battery, and the first two digits in the four digits are the diameter dimensions of the battery, and the latter two is a high dimension with a decimal point. For example, the diameter of CR1220 is 125 mm (excluding the number of decimal points), which is 20mm height. This model representation is internationally universal.

Such buckle batteries are often used in clock, calculator, electronic notepad, camera, hearing aid, video game console, IC card, backup power supply, etc. 2, lithium-thionyl chloride battery (LISOCL2) lithium-thionyl chloride battery is one of the highest energy, currently 500Wh / kg or 1000Wh / L level. Its rated voltage is 36V, with extremely flat 34V discharge characteristics (can be discharged within 90% capacity range) with medium current discharge, maintaining a lot of change).

The battery can operate in the range of -40 ¡ã C ~ + 85 ¡ã C, but the capacity at -40 ¡ã C is about 50% of the normal temperature capacity. The self-discharge rate is low (annual self-discharge rate is 1%), and the storage life is more than 10 years. A comparison of 1 # (dimensional code d) nickel-cadmium battery and 1 # lithium-thionyl chloride battery is compared: 1 # nickel-cadmium battery is 12V, capacity of 5000mAh; 1 # lithium-thionyl chloride The rated voltage is 36V, the capacity is 10000mAh, and the latter is 6 times more than the energy than the former! Application precautions The above two lithium-ion batteries are disposable batteries, not charging (there is dangerous when charging!); Battery positive and negative There is no short circuit; it is not possible to excessively discharge (exceeding maximum discharge current discharge); when the battery is used to terminate the discharge voltage, it should be taken in time from the electron product; the use of the battery is not squeezed, incinerated and disassembled; can not exceed the specified temperature range use.

Since the voltage of the lithium ion battery is higher than the normal battery or nickel-cadmium battery, do not make mistakes to avoid damage to the circuit. By familiar with Cr, ER can understand its type and rated voltage. When purchasing a new battery, be sure to buy according to the original model, otherwise it will affect the performance of electronic products.

Case: Recently, some children have been trained to make robots, very forward-looking parents feel that I am willing to give me the child in the background of my engineer. In fact, as an engineer, it is to use some game tools (similar to Arduino, Raspberry Pivoting to reduce development difficult development board), let your child contact hardware and software in advance, and some control, sensor-related knowledge. But the children are still very happy to participate.

Because the children are so small, they are assembled a smart robot, really very accomplishment. The children are still very happy. However, the problem of reality is coming, because the current design is, power supply directly from high energy consumption such as motor driver, servo, etc.

When children play the happiest, I found that the battery is dead. Many children do not turn off the power in time after the robot works. Overlapping.

Finally, we have a lot of scrap batteries. So we have to rectify existing circuits. But the workload of the change is relatively large, and the inventory of existing products cannot be used, resulting in waste.

Children are scrapped, we are all free to replace, pursue the biggest customer satisfaction. At the beginning, I thought: Using charging treasure, but charging treasure is usually used for mobile phone charging, the maximum output current is generally at 0.5a or 1A (most charging treasure on the market), can not drive the motor driver, and 2A, 3A Charging treasure, cost is too high.

Moreover, the voltage is low, causing a low speed of the motor. So we retrieve existing circuits by adding a lithium-ion battery charge and discharge. This doesn't worry, during assembly, some short circuits, and over-placing cases can prev.