The 18650 lithium battery is a standard lithium-ion battery model established by Sony Corporation of Japan to save costs. The "18" indicates a diameter of 18mm, "65" indicates a length of 65mm, and "0" indicates a cylindrical shape. Below is a detailed introduction to the correct charging and repair methods for 18650 lithium batteries.
I. Correct Charging Method for 18650 Lithium Batteries
1. High-voltage charging: This charging method lacks a dedicated control circuit. It directly charges the battery with a protection board using a 5V power adapter, relying entirely on the high-voltage limit of the protection board. Its characteristics include a very high initial current, which gradually decreases, essentially a float charge. Most batteries that explode are of this type, commonly found in low-end card-operated MP3 players. I don't know much about high-end models – I wouldn't dare say that such expensive devices should have charging circuitry – there are many things that should be done, but even more things that are left undone.
2. Constant Voltage Charging: This method is similar to the previous one. Constant voltage actually means voltage limiting. A relatively precise maximum voltage is set, and then the charger relentlessly charges to that voltage, refusing to stop until it reaches 4.2V. This is commonly known as "foolish charging." If the cutoff voltage of this type of charger is made very precise, it's fine; a slightly lower voltage is actually safer. If it's too high, a protection board is needed. As for the bare battery, good luck to you. This is commonly found in current universal phone chargers and flashlight chargers. The cost of this type of charger is less than one yuan; it's assembled entirely from inferior parts. The retail price on Taobao ranges from 2.00 to 15.00 yuan. How long it will last is uncertain.
3. Constant current charging: This method is derived from the previous two circuits, but the maximum charging current is limited. Constant current and constant voltage are actually current-limiting and voltage-limiting, which is a kind of "foolish charging" method, and still a foolish one. This type of circuit is quite popular, such as those from Nanfu and Hexinyu. After the battery is fully charged, it is not completely cut off, and trickle charging is used instead. It is now believed that prolonged low-current charging is one of the reasons for the gas swelling of 18650 lithium batteries.
4. Intelligent Charging: This is currently considered a more ideal charging management method. Following the charging algorithm mentioned at the beginning of this section, it is integrated into a very small surface-mount IC. The peripheral circuitry is simple, stable, and reliable, such as TP4054/4055/4056/4057, TP4002/5000, MAX1879, etc. A key feature of this chip is that it monitors both voltage and current simultaneously when determining whether the battery is fully charged. Charging stops at 4.2V or when the charging current is less than 0.01C (usually around 50mA). Once fully charged, charging completely stops, without trickle charging, but the voltage is constantly monitored. If the 18650 lithium battery voltage drops to a certain value, charging will resume.
It's important to note that 18650 lithium batteries enter a dormant state after being stored for a period of time, at which point their capacity is lower than normal, and their usage time is shortened. However, lithium-ion batteries are easily activated; they can be activated and restored to normal capacity after just 35 normal charge-discharge cycles. Due to the inherent characteristics of lithium-ion batteries, they have virtually no memory effect. Therefore, no special methods or equipment are required to activate a new lithium-ion battery in a user's mobile phone.
Lithium-ion batteries do not require any special activation method; they will activate naturally during normal use. Insisting on using the commonly circulated method of charging for 12 hours three times to activate them will actually be ineffective.
If the original charger's protection and control circuitry are of good quality, it provides a fairly good guarantee of protection for the 18650 lithium battery. Charge it according to the standard time and procedure, even for the first three times.
II. Repair Methods for 18650 Lithium Batteries
1. Over time, the metal surface of a lithium-ion battery will oxidize to a certain extent, which can lead to poor contact between the battery and the phone, resulting in a shorter battery life. You can use an eraser or other cleaning tools to remove the rust on the surface and improve the contact between the battery and the phone.
2. Low temperatures can alter the electrolyte inside an 18650 lithium battery, promoting chemical reactions in a battery that has just been frozen. The use of a lithium-ion battery is essentially a charge-discharge process. During this process, negative and positive charges collide with each other. Batteries become less durable over time because at normal room temperature, the kinetic energy inside electrons is relatively high, making the battery more active and prone to leakage. Placing a lithium-ion battery in a low-temperature environment significantly alters the microstructure of the lithium film and electrolyte on the battery surface, as well as their interfaces, leading to temporary inactivity and reduced leakage current. Therefore, after recharging, the phone's standby time will increase.
3. Deeply discharging a mobile phone involves depleting its internal electrical energy to achieve a deeper recharge. This requires unconventional methods. One method involves connecting the phone to a 1.5V light bulb. The charge from the 18650 lithium battery will be transferred to the light bulb until it is completely discharged.
(1) After you have used up all of your 18650 lithium batteries, take them out and treat them with temperature. The battery will have a much shorter lifespan if the temperature is unstable because the battery is empty and a significant portion of the lithium ions have memory charge. This method can release some of the memory charge. In winter, put them outside for a while and then bring them back inside.
(2) Another method is to remove the battery and leave it for about a week to slowly deplete the power. You should first use a device to completely deplete the power before fully charging it. After fully charging, disconnect and recharge it. Repeat this several times. This method is definitely effective.
Because of their high capacity per unit density, 18650 batteries are mostly used in laptop batteries. In addition, due to their excellent stability during operation, 18650 batteries are widely used in various electronic fields: commonly used in high-end flashlights, portable power supplies, portable instruments, portable lighting equipment, portable printers, industrial instruments, medical instruments, etc.
