You must know the correct use of lithium batteries

Have to look at the correct use of the battery

1. Recognize the memory effect (mainly talking about nickel-cadmium and nickel-metal hydride batteries, not interested can skip directly to see the second)

The battery memory effect refers to the reversible failure of the battery, that is, the performance of the battery that can be re-recovered after the failure, and the memory effect is that the battery automatically maintains this specific tendency after being subjected to a specific working cycle for a long time, which is first defined in the nickel-cadmium battery. The nickel-cadmium bag battery has no memory effect, the sintered battery has a memory effect, and the current nickel metal hydrogen (commonly known as nickel-hydrogen) battery is not bound by this memory effect definition.

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 memory effects has strict specifications and an operational process, and improper operation can be counterproductive.

For nickel-cadmium batteries, the normal maintenance is regular deep discharge: an average of one month (or 30 cycles) for a deep discharge (discharge to 1.0V / per section, foreigners called exercise), the usual 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, you must have a special equipment or line to complete the work 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, the capacity recovery cannot be performed with exercise. 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 nickel-metal hydride 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, and almost no recondition is used.

Recommendation 1: It is not necessary to discharge the 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 polarity of the battery 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 manufacturer of lithium-ion batteries. The lithium-ion battery has to go through the following process before leaving the factory:

Lithium-ion battery shell infusion of electrolyte --- sealing --- formation, is constant pressure charging, and then discharge, so that several cycles, so that the electrode fully wet the electrolyte, fully activated, to meet the capacity requirements, this is activated Process---dividing, is to test the battery capacity to select different performance (capacity) of the battery to classify, classify the battery, perform capacity matching, etc., so that the lithium-ion battery has been activated to the user's hand. The nickel-cadmium battery and nickel-hydrogen battery that we all use are also turned into the factory after activation. Some of the batteries need to be in the open state during the activation process. After the activation, the battery is sealed. This process can only be completed by the battery manufacturer. It is.

There is a problem here, that is, the battery from the 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 the manufacturer recommends the first use The battery is preferably subjected to a complete charge and discharge process 3 to 5 times in order to eliminate the passivation of the electrode material to achieve maximum capacity.

In the three national standards for nickel-metal hydride, nickel-cadmium and lithium-ion batteries issued in 2001, the initial capacity test has clearly defined that the battery can be deep-charged 5 times deep, and once it meets the requirements, the test it can stop, which explains me very well.

So it is ok to call it "second activation". The "new" battery that the user uses for the first time should try to perform several deep charge and discharge cycles.

However, according to my test (for lithium-ion batteries), the lithium-ion battery with a storage period of 1 to 3 months is subjected to deep-filling and deep-discharging, and the capacity increase phenomenon is almost non-existent. The panel discussion report on battery activation)

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

This problem is closely related to the battery activation problem above. Let's set the factory battery to the user's hand to have the phenomenon of electrode passivation. In order to activate the battery for deep charge and deep discharge cycle 3 times, in fact, this problem is converted into deep charge is not to For 12 hours, then another piece of my article "On the charging time of mobile phone batteries" has already answered this question.

The answer is that you don't need to charge for 12 hours.

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 require 12 hours, and the constant current and constant voltage charging of lithium-ion batteries The feature determines its deep charging time without 12 hours.

For lithium-ion batteries, some people will ask, since the current of the lithium-ion battery in the constant voltage stage is gradually decreasing, is it true when the current is small to infinity, I have drawn the current in the constant voltage phase to reduce the time. Curve, it is fitted to the curve multiple times, and it is found that this curve can be close to zero current with the function of 1/x. In actual test, because of the self-discharge phenomenon of the lithium ion battery itself, this zero current is never reachable. .

Take a 600mAh battery as an example, set the off current to 0.01C (6mA), its 1C charging time does not exceed 150 minutes, then set the off current to 0.001C (0.6mA), its charging time may be 10 hours - -- This is impossible to obtain accurately due to the accuracy of the instrument, but the capacity obtained from 0.01C to 0.001C is calculated to be only 1,7mAh, and more than 7 hours of multi-use is exchanged for less than three thousandths. The capacity is not of 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 the minimum current judgment stage. Generally, after 150 minutes, it is 100% full, and many mobile phones are It is pulsed 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, 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 a lithium-ion battery in a state of no charge (and no discharge).

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 the best?

There is a saying that if the rechargeable battery is used properly, it will have the best state in a certain cycle range, that is, the maximum capacity. This is divided into the case, sealed nickel-metal hydride 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 a 120-cycle nickel-hydrogen battery with a factory capacity of 1000 mAh, its capacity may reach 1100 mAh. I can see this description on the graphs describing the cycle characteristics of nickel-based batteries in the technical specifications of almost all Japanese NiMH battery manufacturers.

The nickel-based battery has the best condition, and generally reaches its 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 to make your lithium-ion battery fully display its capacity, we must pay close attention to the use of the environment to prevent high and low temperature phenomena. For example, the mobile phone is placed in the front of the car, and it is easy to make it exceed 60 degrees at noon. The battery standby time of users in the north, 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 battery, in a certain current range (1.5C~0.5C), increasing the constant current value of constant current and constant voltage charging mode cannot shorten the time of charging 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 method, the mobile phone does not fully utilize the direct charging output capability, the direct charging works in the constant voltage section, the output is 5.3V, 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 direct charging of the motorola has its output of 5.0V1A. In fact, the battery is really charged with 500mA, because the battery capacity of the phone is only 580mAh.

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

B, charging management is pulse mode, this charging mode, the mobile phone completely utilizes the direct current limiting current, which is 600mA on the battery. At this time, the direct charging output current 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 it a life of less than one cycle of charge and discharge?

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 a long time, the definition of the number of cycles, the actual user use is ever-changing, because the conditions are different The tests 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 cutoff cycle for a constant current 1C discharge system. When there is a discharge time of 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 by 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 completely different. For example, the above other conditions are unchanged. Only the constant voltage of 4.2V is changed to a constant voltage of 4.1V. The cycle life test of the same type of battery is performed. So, this battery is not 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, 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 the explanation. When you talk about the number of cycles, you can't ignore the conditions of the loop.

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 way to measure the cycle life, that is, the time, the life expectancy 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 lithium The aging effect of the ion battery (refer to point 9), I think it is more reasonable to use the time to express the cycle life.

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

Therefore, for lithium-ion batteries, it is not necessary 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 make good use of them this feature.

8. The higher the battery capacity, the better?

Different models (especially different volumes) of the battery, the higher his capacity, the longer the use of the time is, throwing away the volume and weight factor, of course, the higher 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 stability is reduced. As a result, after a few dozen cycles, the high capacity battery has a rapid capacity failure and a low capacity. The battery is still strong, many domestic battery manufacturers often use this way to obtain high-capacity batteries, and 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 fully charged 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. Loss, this is because the positive and negative materials of lithium-ion batteries have started its depletion history, different temperatures and battery fullness from the factory, and the aging effects are different. The following data is taken from the reference [1] to the percentage form is listed:

Storage temperature -40% charge status -------100% charge status

0 degrees -------98% (after one year)-----94% (one year later)

25 degrees ------96% (one year later)-----80% (one year later)

40 degrees ------ 85% (one year later) --- 65% (one year later)

60 degrees ------75% (after one year)-----60% (after 3 months)

It can be seen that the higher the storage temperature and the more saturated the battery is, the more the capacity loss will be, so it is not recommended to store the lithium-ion battery for a long time. On the contrary, the manufacturer should recycle it like the rotten food, and the user should pay close attention to it, the date of manufacture of the battery.

If the user has an empty battery in his hand, the recommended storage conditions for the expert are a charge level of 40% and a storage temperature of less than 15 degrees or less.

Nickel-metal hydride batteries and nickel-cadmium batteries are almost immune to this aging effect. Long-term storage of nickel-based batteries can restore their original capacity after several deep deep charges.

10. Is it useful to charge more than an hour after the green light of the charger is turned on?

The green light is only an indication. Whether it is fully charged or not depends on the control and judgment of the charging process of the battery charging, and the 4.2V lithium ion battery is taken as an example to discuss this problem.

The first is control, which controls the output of the battery to be constant current first, and then constant voltage (current is gradually reduced)

Then it is judged that when the current is less than a certain current value, the green light is displayed, because the accuracy of the analog-to-digital conversion and its own voltage accuracy are limited. The charger usually sets the current value to 50 mA. At this time, the green light is displayed, then the battery It is still less than 10% of its true fullness. (According to my test, the current lithium-ion battery is 50% cut-off, the capacity can reach 95%, the charging acceptance is greatly improved. The problem now is the charging. What are you doing?

A. If it continues, the charger completely shuts down the charging circuit and does not continue to perform constant voltage charging. Then it is not helpful to place it for 10 hours on the charger. Many charger design schemes are like this, such as TI (Texas Instruments). The BQ2057 series charging chip is the same as the linear LT1800 series.

B. The charger continues to carry out constant voltage charging, and the voltage is strictly controlled to not exceed 4.2V. Undoubtedly charging for another hour, it can really increase the battery capacity.

C, the charger continues to charge, but its current control is very bad, accidentally make the battery exceeds 4.2V, and continue to run, because the lithium-ion battery can not absorb any overcharge, continue to apply current to the battery, it will cause This consequence, then overcharge occurs, this is of course a badly designed charger, such as a common "filled egg" that can charge a lithium-ion battery and can charge a nickel-hydrogen battery for more than ten dollars.

D. There is also a charging management chip, such as Maxim's 1679 chip, which is the same as many mobile phone charging management. It uses pulsed charging. When it displays green light, the lithium-ion battery is 100% full, of course. After another hour, it will not overcharge, and obviously it is doing nothing.

The user does not actually know what the cradle is doing after the green light is on, A or B or D, it is possible that the cradle instruction does not write these things, and excludes the unqualified cradle. We should actually believe the qualified and original seat. If the green light is on, why not take it down? This does not have much impact on the user. The filling is not enough and does not affect the cycle life (as mentioned in point 7 above). 95% of the capacity is also acceptable, unless there is a lover who can analyze his own charger in depth. In that way, charging, otherwise we may wish to ------after the green light is taken down.

11. Is the charger charging more than straight?

There is no such thing as a full charge than a direct charge. There is no such thing as a direct charge that is more than a full charge. What is important is whether their charging method can charge the battery the fastest and the largest.

The page contains the contents of the machine translation.