Lithium battery charging knowledge

Charging voltage
Generally, the battery voltage of a mobile phone is written as 3.7V, but the voltage of a general charger is written as 5V, but it will not affect the use, because there is a charging management chip inside the mobile phone that is responsible for stepping down the constant current charging.
No. 5 cylindrical lithium battery, that is, the 14500 battery. The battery voltage is adjusted to 3.0V suitable for small appliances through the technology of lithium battery voltage regulator.
Regarding the "activation" problem of newly purchased lithium-ion batteries, many people say that the charging time must be more than 12 hours, and it must be repeated three times in order to activate the battery. This statement of "charging for more than 12 hours for the first three times" is obviously a continuation of the statement from nickel batteries (such as nickel-cadmium and nickel-metal hydride). So this statement can be said to be a misunderstanding from the beginning. The charging and discharging characteristics of lithium batteries and nickel batteries are very different, and it can be told very clearly that all serious formal technical data emphasize that overcharging and over-discharging will cause great damage to lithium batteries, especially liquid lithium-ion batteries. Therefore, it is best to charge according to standard time and standard methods, especially not to charge for more than 12 hours.
The battery also needs to be activated. However, this process is completed by the manufacturer and has nothing to do with the user, and the user is not capable of completing it. The real activation process of lithium batteries is as follows: the lithium-ion battery shell is infused with electrolyte-sealed-formed, that is, constant voltage charging, and then discharged, so that the electrodes are fully infiltrated with electrolyte and fully activated until the capacity reaches the required level. This is the activation process-capacity division, which means that the lithium-ion battery is already activated when it leaves the factory and reaches the user. In addition, the activation process of some batteries requires the battery to be in an open state and then sealed after activation.
The instructions of some products state that it is recommended that users fully charge and discharge the mobile phone for the first three uses. In fact, the fact is that after the battery leaves the factory, is sold, and then is in the hands of the user, it will take a period of time, one month or several months. In this way, the electrode material of the battery will be "passivated", and the capacity will be lower than the normal value at this time, and the use time will also be shortened. However, lithium batteries are easy to activate. As long as 3-5 normal charge and discharge cycles are passed, the battery can be activated and restored to normal capacity. Due to the characteristics of the lithium battery itself, it has almost no memory effect. Therefore, users do not need special methods and equipment during the activation process of new lithium batteries.
Long charging and deep charging
Long charging may lead to overcharging. Lithium batteries or chargers will automatically stop charging after the battery is fully charged. There is no so-called "trickle" charging that lasts for more than 10 hours like nickel chargers. In other words, if the lithium battery is fully charged, it is useless to put it on the charger. No one can guarantee that the characteristics of the battery's charge and discharge protection circuit will never change and the quality will be foolproof, so the battery will be on the edge of danger for a long time. This is another reason to oppose long charging.
For some machines, if the charger is not removed after charging for more than a certain period of time, the system will not only not stop charging, but will also start a discharge-charge cycle. Perhaps the manufacturer has its own purpose for this practice, but it is obviously not good for the life of the battery. At the same time, long charging takes a long time and often needs to be done at night. Judging from the situation of China's power grid, the voltage at night in many places is relatively high and fluctuates greatly. As mentioned earlier, lithium batteries are very delicate. They are much less resistant to fluctuations in charge and discharge than nickel batteries, so this brings additional dangers.
In fact, shallow discharge and shallow charge are more beneficial for lithium batteries. Only when the power module of the product is calibrated for lithium batteries, deep discharge and deep charge are necessary. Therefore, products powered by lithium batteries do not have to stick to the process. Everything should be convenient and charged at any time.
Overcharge and over discharge
The rated voltage of lithium-ion batteries is generally 3.7V due to material changes, and the positive electrode of lithium iron phosphate (hereinafter referred to as ferrophosphorus) is 3.2V. The international standard for the termination charge voltage when fully charged is 4.2V, and ferrophosphorus is 3.6V. The termination discharge voltage of lithium-ion batteries is 2.75V~3.0V (domestic battery manufacturers give the operating voltage range or the termination discharge voltage, and the parameters are slightly different, generally 3.0~2.75V, and ferrophosphorus is 2.5V.). Continuing to discharge below 2.5V (ferrophosphorus 2.0V) is called over discharge (the international standard is a minimum of 3.2v, and ferrophosphorus 2.8v). Low-voltage over discharge or self-discharge reaction will cause the lithium ion active material to decompose and destroy, and it may not be restored. Any form of overcharging of lithium-ion batteries will cause serious damage to battery performance or even explosion. Overcharging of lithium-ion batteries must be avoided during the charging process.