How to charge and discharge lithium batteries correctly

In the use of lithium batteries, it should be noted that after the battery is placed for a period of time, it enters a sleep state. At this time, the capacity is lower than the normal value, and the use time is also shortened. However, the lithium battery is easy to activate, as long as the normal charge and discharge cycle is 3-5 times, the battery can be activated to restore normal capacity. Due to the characteristics of the lithium battery itself, it is determined that it has almost no memory effect. Therefore, the new lithium battery in the user's mobile phone does not require special methods and equipment during the activation process. Not only in theory, but from my own practice, it is best to use a standard method of charging "natural activation" method from the beginning.

For the "activation" problem of lithium batteries, many sayings are: charging time must be more than 12 hours, repeated three times in order to activate the battery. This statement that "the first three charges have to be charged for more than 12 hours" is obviously a continuation of the nickel battery (such as nickel cadmium and nickel hydride). So this kind of statement can be said to be misinformation at the beginning. The charge and discharge characteristics of lithium and nickel batteries are very different, and it is very clear to tell you that all the serious official technical information I have reviewed emphasizes that overcharge and over discharge will be lithium batteries, especially liquid lithium. Ion batteries cause great damage. Therefore, charging is preferably performed in accordance with standard time and standard methods, especially for ultra-long charging of more than 12 hours. Usually, the charging method described in the instruction manual is the standard charging method.

At the same time, long charging takes a long time and often needs to be carried out at night. In the case of China's power grid, the voltage at night is high in many places and fluctuates greatly. As mentioned above, the lithium battery is very delicate, it is much less resistant to fluctuations in charge and discharge than nickel, and this brings additional danger.

In addition, another aspect that cannot be ignored is that lithium batteries are also not suitable for over-discharge, and over-discharge is also disadvantageous for lithium batteries.

Tools/raw materials

Lithium battery, nickel metal hydride battery, lithium battery charger, nickel metal hydride battery charger

Step / method

When should I start charging during normal use?

This statement can often be seen on the forum, because the number of charge and discharge is limited, so the battery should be recharged as much as possible. But I found an experimental table on the charge and discharge cycle of lithium-ion batteries. The data on cycle life are listed below:

Cycle life (10% DOD) : >1000 times

Cycle life (100% DOD) : >200 times

Among them, DOD is the abbreviation of depth of discharge. As can be seen from the table, the number of chargeable is related to the depth of discharge, and the cycle life at 10% DOD is much longer than that of 100% DOD. Of course, if you convert to the relative total capacity of the actual charge: 10% * 1000 = 100, 100% * 200 = 200, the latter's full charge and discharge is still better, but the former netizen’s statement to do some correction: in normal In this case, you should reserve the charge according to the principle that the remaining battery power is used up and recharge, but if your battery is not likely to last for two hours on the second day, you should start charging in time. Of course, if you are willing carrying the charger to the office is another matter.

You need to charge to cope with the expected inconvenience or when the conditions are not allowed to charge, even if the battery still has a lot of power, then you only charge in advance, because you have not really lost "1" charge cycle life, that is, " 0.x" only, and often this x will be small.

The principle that the remaining battery power is used up and refilled is not to go to extremes. One of the more widely spread arguments like long charging is that "try to run out of battery power, it is best to use automatic shutdown." This practice is actually only a nickel battery. The purpose is to avoid memory effects. Unfortunately it is also circulating on lithium batteries. The battery is too low due to excessive discharge, so that it does not have normal charging and power-on conditions.

The correct way to charge lithium batteries

To sum up, my most important tips on the charge and discharge of lithium batteries in use are:

1. Charge according to standard time and procedures, even if it is the first three times;

2. When the power is too low, you should start charging as soon as possible;

3. The activation of the lithium battery does not require a special method, and the lithium battery will naturally activate during normal use. If you insist on using the "first three 12-hour long charge activation" method that is circulated, it will not actually work.

Therefore, all the pursuit of 12 to 16 hours of ultra-long charging and the use of lithium batteries to automatically shut down is wrong. If you have done it in the wrong way, please correct it in time, maybe it is not too late.

Precautions

Under the condition that the original charger's own protection and control circuit is of good quality, the protection of the lithium battery is quite guaranteed. So the understanding of the charging rules is the key point, and in some cases it is also possible to make some concessions. For example, if you think the battery must be charged before you go to sleep at night, you can also start charging before going to bed. The point is that you should know what the right approach is and don't deliberately follow the wrong way.

The life of electricity is generally 300-500 charge cycles. Assuming that the amount of power supplied by a full discharge is 1Q, if the power consumption is reduced after each charging cycle, the lithium battery can provide or supplement 300Q-500Q power in its lifetime. Therefore, if you charge 1/2 each time, you can charge 600-1000 times; if you charge 1/3 each time, you can charge 900-1500 times. By analogy, if you charge randomly, the number of times is variable. In short, no matter how charged, the total power added to 300Q-500Q is constant. Therefore, we can also understand that the life of the lithium battery is related to the total charge of the battery, regardless of the number of times of charging. The effect of deep charge and shallow charge on lithium battery life is not much different. Then, some manufacturers said in the propaganda, "A certain strong lithium battery can be charged more than 1500 times." This is purely bullying consumer’s ignorance.

In fact, shallow charge is more beneficial for lithium battery. Only when the power module of the product is calibrated for lithium battery, it is necessary to deep charge. Therefore, products that use lithium-ion power supply do not have to be constrained by the process. Everything is convenient and can be charged at any time without worrying about affecting life.

The page contains the contents of the machine translation.