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How to properly use lithium manganese oxide lithium ion battery

How to properly use lithium manganese oxide lithium ion battery

Release date:2018-11-16 author: clicks:

1. Recognize the memory effect


The battery memory effect refers to the reversible failure of the battery, that is, the performance that can be restored after the battery fails. The memory effect of a ternary lithium-ion battery means that the battery automatically maintains this particular tendency after being subjected to a specific duty cycle for a long time. This is the earliest definition of nickel-cadmium batteries, nickel-cadmium bag batteries have no memory effect, and sintered batteries have a memory effect. Today's nickel metal hydride (commonly known as nickel hydride) batteries are not subject to the definition of this memory effect.


Because of the improvement of the modern nickel-cadmium battery process, the above memory effect has been greatly reduced, and another phenomenon replaces this definition, which is the "lattice" of nickel-based batteries. Generally, nickel-cadmium batteries are subject to these two types. The combined effect of the effect, while the nickel-hydrogen battery is only affected by the "lattice" memory effect, and the impact is smaller than that of the nickel-cadmium battery.


In practical applications, the method of eliminating the memory effect of the ternary lithium ion battery has strict specifications and an operation procedure. Improper operation can be counterproductive.


For nickel-cadmium batteries, the normal maintenance is regular deep discharge: a deep discharge is performed every one month (or 30 cycles) (discharge to 1.0V/per node, foreigner is called exercise), lithium iron phosphate lithium ion battery Normal use is to use light batteries or use shutdown to ease the formation of memory effects, but this is not exercise, because the instrument (such as mobile phone) will not use 1.0V / every section to shut down, must have special equipment or The line is used to do the job, but fortunately many NiMH battery chargers have this feature.


For nickel-cadmium batteries that have not been exercised for a long time, due to the accumulation of memory effects, it is impossible to use exercise for capacity recovery. In this case, a deeper discharge (foreigner called recondition) is required, which is a battery with a small current for a long time. A process of discharging to 0.4V per section requires professional equipment.


For lithium iron phosphate lithium-ion batteries, the frequency of exercise is about once every three months to effectively alleviate the memory effect. Because the cycle life of nickel-metal hydride batteries is much lower than that of nickel-cadmium batteries, the recondition method is hardly used.


▲Recommendation 1: It is not necessary to discharge lithium iron phosphate lithium ion battery before each charge, and it is harmful because the battery life is unnecessarily shortened.


▲Recommendation 2: It is not advisable to use a resistor to connect the positive and negative poles of the battery for discharge. The current cannot be controlled, it is easy to over-discharge to 0V, and even the battery polarity of the series battery pack is reversed.


2. Does the battery need to be activated?


The answer is that the battery needs to be activated, but this is not what the user has to do. I have visited the lithium ion battery manufacturer. The lithium ion battery has to go through the following process before leaving the factory:


The ternary lithium-ion battery shell infusion electrolyte---sealing----chemicalization, is constant voltage charging, and then discharge, so that several cycles, so that the electrode fully wet the electrolyte, fully activated, to meet the requirements of capacity, this It is the activation process---dividing, that is, testing the capacity of the battery to select different performance (capacity) of the battery to classify, classify the battery, and perform capacity matching. The lithium-ion battery thus come out has been activated to the user. The nickel-cadmium batteries and nickel-metal hydride batteries that we all use are also activated after they are activated. Some of these batteries require the battery to be in an open state. After activation, the battery is sealed. This process can only be completed by the battery manufacturer.


There is a problem here, that is, the battery from the lithium iron phosphate lithium ion battery factory to the user's hand, this time is sometimes very long, short one month, long half year, this time, because the battery electrode material will be passivated, so It is recommended that the battery used for the first time be fully recharged 3 to 5 times in order to eliminate the passivation of the electrode material and reach the maximum capacity.


Three of the nickel hydrogens were issued in 2001. In the national standard of nickel-cadmium and lithium-ion batteries, the initial capacity detection is clearly defined, and the battery can be deep-filled for 5 times. When one time meets the requirements, the test can be stopped. This is a good explanation of the phenomenon I am talking about.


★ So it is ok to call it “Second Activation”. The “new” battery used by the user for the first time should be subjected to several deep charge and discharge cycles.


● However, according to my test (for lithium-ion batteries), lithium manganese oxide lithium ion battery with a storage period of 1 to 3 months

, it is deep-filled and deep-circulated, and its capacity increase phenomenon is almost non-existent. (I have a test report on battery activation in the panel)


3. Do you have to charge for 12 hours in the first three times?


Early mobile phone NiMH batteries, because of the need for replenishment and trickle charging, to achieve the most perfect state of fullness, may take about 5 hours, but it does not need 12 hours. The constant current and constant voltage charging characteristics of lithium iron phosphate lithium ion battery determine that its deep charging time does not need 12 hours.


For lithium-ion batteries, some people will ask, since the current of the lithium-ion battery in the constant-voltage phase is gradually reduced, is it true when the current is small to infinity? I once plotted the curve of current reduction in time during constant voltage, and performed multiple curve fittings on it. It was found that this curve can be approximated to zero current with the function of 1/x. Actually, the lithium ion battery itself exists. Self-discharge, this zero current is never possible to reach.


Take a 600mAh battery as an example, set the off current to 0.01C (ie 6mA), its 1C charging time does not exceed 150 minutes, then set the off current to 0.001C (ie 0.6mA), its charging time may be 10 hours - -- This is not precisely available due to the accuracy of the instrument, but the capacity obtained from 0.01C to 0.001C is calculated to be only 1.7mAh, which is more than 7 hours in exchange for more than three thousandths. Capacity does not have any practical significance.


What's more, there are other charging methods, such as pulse charging, which allows the lithium-ion battery to reach the 4.2V limit voltage. It does not have a minimum current judgment stage. Generally, it is 100% full after 150 minutes. Many mobile phones use pulse charging.


Some people used to display the fullness of the mobile phone, and then use the charger to charge to confirm the fullness of the phone. This test method is not rigorous.


First of all, the green light is not a basis for detecting the true fullness or not.


★★ The only final way to detect the saturation of a lithium-ion battery is to test the voltage of the lithium-ion battery in the uncharged (and non-discharged) state.


The so-called constant voltage phase current reduction is the real purpose of gradually reducing the additional voltage generated by the charging current in the internal resistance of the battery. When the current is as small as 0.01C, such as 6mA, this current is multiplied by the internal resistance of the battery (generally 200 Within milliohms) is only 1mV, and it can be considered that the voltage at this time is the battery voltage without current.


Secondly, the reference voltage of the mobile phone is not necessarily equal to the reference voltage of the charger. The mobile phone thinks that the fully charged battery has reached the charger, but the charger does not think that it is full, but continues to charge.


4. Is the rechargeable battery in the best condition?


There is a saying that lithium manganese oxide lithium ion battery rechargeable battery is used properly and will have the best state in a certain cycle range, that is, the largest capacity. This is divided into the case, sealed NiMH batteries and nickel-cadmium batteries, if used properly (such as regular maintenance, to prevent the generation and accumulation of memory effects), generally reach the maximum value of its capacity in 100 ~ 200 cycles, such as After using 120 cycles of 1000 mAh nickel-metal hydride battery, the capacity may reach 1100 mAh. I can see the cycle characteristics of nickel-based batteries in the technical specifications of all Japanese nickel-hydrogen battery manufacturers. To such a description.


★ Nickel-based batteries have the best condition, generally reach their maximum capacity between 100 and 200 cycles.


For liquid lithium-ion batteries, there is no such hump phenomenon in circulating capacity. From the time when the lithium-ion battery is shipped to the end of the battery, the capacity is used once less. I have never seen signs of capacity recovery when I am doing cycle performance on lithium-ion batteries.


★ Lithium-ion batteries are not optimal.


It is worth mentioning that lithium-ion batteries are more susceptible to different performances due to changes in ambient temperature. They exhibit the best performance at ambient temperatures of 25 to 40 degrees, and their performance is greatly compromised at low or high temperatures. . In order for your lithium-ion battery to fully display its capacity, you must pay close attention to the use of the environment to prevent high and low temperature phenomena, such as the phone placed in the front of the car, the sun at noon can easily make it more than 60 degrees, north The user's battery standby time, under the same network conditions, there is no long-term user in the South.


5. Is the charging current bigger, the faster the charging?


This issue has already been addressed in the article "On the charging time of mobile phone batteries". For nickel-based batteries with constant current charging, this can be said, and for lithium-ion batteries, this is not completely correct.


★★ For the charging of lithium-ion batteries, in a certain current range (1.5C~0.5C), increasing the constant current value of the constant current and constant voltage charging mode does not shorten the time for charging the lithium ion battery.


6. Is the output current of the direct charge equal to the charge current?


This is to discuss the charging method of the mobile phone. For the charging management in the mobile phone, set the output of the same direct charge (actually called the power adapter) such as: 5.3V600mA


A. Charging management is the switching mode (high-frequency pulse width adjustment PWM mode). This charging mode does not fully utilize the direct charging output capability of the mobile phone. The direct charging works in the constant voltage section and outputs 5.3V. At this time, the real charging current It is adjusted by the charging management of the mobile phone, and it must be less than 600mA, generally 300~400mA. At this time, the output current of the direct charge that everyone sees is not the charging current of the mobile phone. For example, many of Motorola's direct charge output is 5.0V1A, and the battery is really charged with 500mA, because the battery capacity of the mobile phone is only 580mAh.


★At this time, the output current of the direct charge superscript is not equal to the actual charging current.


B. The charging management is pulse mode. In this charging mode, the mobile phone completely utilizes the current limiting current of the direct charging, that is, 600mA is used on the battery. At this time, the output current of the direct charging is the charging current.


Of course, the above refers to the constant current phase of the lithium ion battery or the charging of the nickel hydrogen battery.


If the phone does not have charge management, the management of charging is moved to direct charge. For example, many CDMA phones are like this. There is nothing to say about this. Its output is very clear, such as output: 4.2V500mA, this is a lithium-ion battery. Constant current and constant pressure two data


7. Is the cycle charge and discharge once less life?


The cycle is the use, we are using the battery, the concern is the time of use, in order to measure how long the rechargeable battery can be used for such a performance, the definition of the number of cycles is specified. The actual user usage is ever-changing, because the tests with different conditions are not comparable, and the definition of cycle life must be standardized for comparison.


The national standard specifies the cycle life test conditions and requirements for lithium-ion batteries: charging at a constant temperature and constant voltage 1C charging system for 150 minutes at room temperature of 25 degrees, discharging to a 2.75V cut-off cycle for a constant current 1C discharge system. When the discharge time is less than 36 minutes, the test is over and the number of cycles must be greater than 300 times.


Explanation:


A. This definition stipulates that the test of cycle life is carried out in deep charge and deep release.


B. It is stipulated that the cycle life must exceed 60 times after the execution of this mode, and the capacity is still more than 60%.


In fact, the number of cycles obtained by different circulation systems is quite different. For example, the other conditions above are unchanged. Only the constant voltage of 4.2V is changed to the constant voltage of 4.1V. The cycle life test of the same type of battery is performed. So, this battery is no longer a deep charge method. In the end, the cycle life can be increased by nearly 60%. If the cutoff voltage is increased to 3.9V for testing, the number of cycles should be increased several times.


This statement about the lack of life once in a loop has been discussed by many friends. I just added that we can't ignore the conditions of the loop when we talk about the number of loops.


● It doesn't make sense to talk about the number of loops, because the number of loops is a means of detecting battery life, not the purpose!


▲ Misunderstanding: Many people like to use the mobile phone lithium-ion battery to automatically shut down and recharge. This is completely unnecessary.


In fact, it is impossible for the user to use the battery according to the national standard test mode. No mobile phone will be turned off at 2.75V, and its discharge mode is not a high current constant current discharge, but a GSM pulse discharge and a small current discharge mix. The way.


There is another measure of cycle life, which is time. Some experts have suggested that the life of a general-purpose lithium-ion battery is 2 to 3 years, combined with the actual situation, such as the termination of life with 60% capacity, plus the aging effect of lithium-ion battery (refer to point 9), with time To express the cycle life I think is more reasonable.


The charging mechanism of lithium manganate lithium ion battery is similar to that of lithium ion battery. It is a current limiting method. The method of using it is shallow filling. His life expression is time, no number, such as 10 years.


★★★ Therefore, for lithium-ion batteries, there is no need to use the shutdown and recharge. Lithium-ion batteries are suitable for use at any time. This is one of his biggest advantages for NiMH batteries. Please take advantage of them. This feature.


8. The higher the battery capacity, the better?


For different models (especially different volumes), the higher the capacity, the longer it will be used. Aside from the factors of volume and weight, of course, the higher the capacity, the better.


But the same battery model, the nominal capacity (such as 600mAh) is also the same, the actual measured initial capacity is different: for example, one is 660mAh, the other is 605mAh, then 660mAh is better than 605mAh.


The actual situation may be that the capacity is high because the electrode material has more things to increase the initial capacity, and the electrode is used for stability. As a result, after a few dozen cycles, the battery with high capacity is rapidly depleted, and the capacity is low. The battery is still strong. Many domestic battery manufacturers often use this method to obtain high-capacity batteries. The user's standby time after half a year is a mess.


The civilian AA nickel-metal hydride batteries (that is, the fifth battery), generally 1400mAh, but also have the standard ultra-high capacity (1600mAh), the same is true.


★ The cost of increasing the capacity is to sacrifice the cycle life. The manufacturer is not in the modified context of the battery material, it is impossible to really "improve" the battery capacity.


9. Is the full battery stored?


Lithium-ion batteries have a very bad characteristic, that is, the aging of lithium-ion batteries (or aging, foreigners called aging), that is, after a period of storage of lithium-ion batteries, even if they are not recycled, some of their capacity will be permanent. Lost, this is because of lithium

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