How long is the cycle life of ordinary 18650 lithium battery?

At present, the general cycle life of 18650 of 3.7v can reach about 500~1000 times, and the general cycle life of 18650 of 3.2v can reach more than 2000 times. Of course, the premise is the qualified battery produced by the regular manufacturer. If the battery is defective or fake, the life will be very short.

18650 is the ancestor of lithium ion battery -- a standard lithium ion battery model set by SONY of Japan in order to save costs. Among them, 18 indicates the diameter of 18mm, 65 indicates the length of 65mm, and 0 indicates the cylindrical battery.

The common 18650 battery is divided into lithium ion battery and lithium iron phosphate battery. The nominal voltage of lithium ion battery is 3.7v, the cut-off voltage of charge is 4.2v, the nominal voltage of lithium iron phosphate battery is 3.2v, the cut-off voltage of charge is 3.6v, the capacity is usually 1200mah-3350mah, the common capacity is 2200mah-2600mah.

Lithium battery (Li - ion, LithiumIonBattery) : lithium ion battery has a light weight, large capacity, no memory effect, etc, and widely application, many digital devices are used the lithium ion battery as a power source, although its price is relatively expensive. The energy density of lithium ion battery is very high, its capacity is 1.5~2 times of the weight of nickel metal hydride battery, and has very low self-discharge rate. In addition, lithium ion battery has almost no "memory effect" and does not contain toxic substances and other advantages is also an important reason for its wide application. Also please note that the lithium battery external generally marked with English 4.2 Vlithiumionbattery Vlithiumsecondarybattery (lithium battery) or 4.2 (lithium secondary battery), 4.2 Vlithiumionrechargeablebattery (rechargeable lithium battery), so the user must see when buying batteries battery block appearance, prevent because they didn't see the battery type and cadmium nickel, nickel-metal hydride batteries will be mistaken for lithium batteries. Lithium battery standard 3.7v or 4.2v is the same. It is what manufacturer label is different only and oneself. 3.7v refers to the platform voltage (i.e., the typical voltage) discharged during the use of the battery, while 4.2v refers to the voltage when the battery is fully charged. Common 18650 rechargeable lithium battery, the voltage is 3.6 or 3.7 v, the charge is 4.2 v, this has very little to do with power (capacity), 18650 battery capacity of mainstream mah from 1800 to 2600 mah, (more than 18650 power battery capacity in 2200 ~ 2600 mah), the capacity of the mainstream and even more than the 3500 or 4000 mah has (remind everybody, above the nominal 3350 mah on the market of domestic batteries are likely to false, the current domestic production of the maximum capacity is 3350 mah.).

Generally, the no-load voltage of lithium battery is considered to be used up when it is below 3.0v (the specific value depends on the threshold value of the battery protection board, for example, there are as low as 2.8v and 3.2v). Most lithium batteries cannot discharge the no-load voltage below 3.2v, or excessive discharge will damage the battery (generally, lithium batteries in the market are basically used with a protective plate, so excessive discharge will also lead to the protection plate can not detect the battery, thus unable to charge the battery). 4.2v is the maximum limiting voltage for battery charging, and it is generally believed that charging the no-load voltage of lithium battery to 4.2v means that the battery is fully charged. In the process of battery charging, the battery voltage gradually rises from 3.7v to 4.2v. Lithium battery charging cannot charge the no-load voltage to more than 4.2v, or it will damage the battery.

Lithium battery standard 3.7v or 4.2v is the same. It is what manufacturer label is different only and oneself. 3.7v refers to the platform voltage (i.e., the typical voltage) discharged during the use of the battery, while 4.2v refers to the voltage when the battery is fully charged. Common 18650 rechargeable lithium battery, the voltage is 3.6 or 3.7 v, the charge is 4.2 v, this has very little to do with power (capacity), 18650 battery capacity of mainstream mah from 1800 to 2600 mah, (more than 18650 power battery capacity in 2200 ~ 2600 mah), the capacity of the mainstream and even more than the 3500 or 4000 mah has (remind everybody, above the nominal 3350 mah on the market of domestic batteries are likely to false, the current domestic production of the maximum capacity is 3350 mah.).

Generally, the no-load voltage of lithium battery is considered to be used up when it is below 3.0v (the specific value depends on the threshold value of the battery protection board, for example, there are as low as 2.8v and 3.2v). Most lithium batteries cannot discharge the no-load voltage below 3.2v, or excessive discharge will damage the battery (generally, lithium batteries in the market are basically used with a protective plate, so excessive discharge will also lead to the protection plate can not detect the battery, thus unable to charge the battery). 4.2v is the maximum limiting voltage for battery charging, and it is generally believed that charging the no-load voltage of lithium battery to 4.2v means that the battery is fully charged. In the process of battery charging, the battery voltage gradually rises from 3.7v to 4.2v. Lithium battery charging cannot charge the no-load voltage to more than 4.2v, or it will damage the battery.

The 18650 battery life theory provides 1,000 cycles of charge. As the density of the unit capacity is very big, so most of the laptop battery, in addition, in 18650 at work stable performance is very good, is widely used in the electronics field: commonly used in high-grade light flashlight, portable power, wireless data transmission, electric thermal clothing, shoes and portable instruments and meters, portable lighting, portable printers, industrial equipment, medical equipment, etc.

18650 means 18mm in diameter and 65mm in length. The model number 5 is 14500, with a diameter of 14mm and a length of 50mm. General 18650 batteries in the industrial use of more, less civil, common also in the notebook battery and high-end flashlight use more.

The 18650 is only the size and model of the battery. According to the battery type, it can be divided into 18650 for lithium ion, 18650 for lithium iron phosphate, 18650 for nickel hydrogen (very rare), and the common 18650 for lithium ion.

Principle of charge and discharge

The working principle of lithium ion battery is its charge and discharge principle. When the battery is charged, lithium ions are formed on the positive electrode of the battery, and the lithium ions generated move to the negative electrode through the electrolyte. Carbon, as a negative electrode, has a layered structure, and it has many micropores. The lithium ions that reach the negative electrode are embedded into the micropores of the carbon layer. The more lithium ions embedded, the higher the charging capacity.

Similarly, when a battery is discharged (the process by which we use the battery), lithium ions embedded in the negative carbon layer escape and move back to the positive electrode. The more lithium ions that return to the positive electrode, the higher the discharge capacity. We usually say the battery capacity refers to the discharge capacity.

It is not difficult to see that during the charging and discharging process of lithium ion battery, lithium ion is in the motion state from positive pole to negative pole to positive pole. If we think of the lithium ion battery as a rocking chair, the two ends of the rocking chair are the two poles of the battery, and the lithium ion is like a good athlete, running back and forth between the two ends of the rocking chair. So the experts have come up with a cute name for the lithium-ion battery: the rocking chair battery.

Charge discharge process

The lithium battery charging control is divided into two stages. The first stage is constant current charging. When the battery voltage is lower than 4.2v, the charger will charge at a constant current. The second stage is the constant voltage charging stage, when the battery voltage is 4.2 V, due to the lithium battery characteristics, if the voltage is high, will damage, the charger voltage will be fixed in 4.2 V, the charging current will be reduced gradually, when the current decreases to a certain value (usually 1/10 set current), to cut off the charging circuit, a complete charging indicator, charging is complete.

Excessive charge and discharge of lithium ion batteries will cause permanent damage to the positive and negative electrodes. Excessive discharge leads to the collapse of the structure of the negative carbon sheet layer, which will make it impossible for lithium ions to be inserted in the charging process. Overcharging causes too many lithium ions to embed themselves in the negative carbon structure, so that some of them can no longer be released.

Some chargers use cheap solutions to achieve, in the control accuracy is not good enough, easy to cause abnormal battery charging, or even damage the battery. When choosing a charger, try to choose a big brand of 18650 lithium ion battery charger. The quality and after-sale guarantee can extend the service life of the battery. The 18650 lithium ion battery charger guaranteed by the brand has four protection functions: short circuit protection, over current protection, over voltage protection and battery reverse connection protection. Overcharge protection: when the charger overcharges the lithium ion battery, in order to prevent the rise of internal pressure caused by temperature rise, the charging state shall be terminated. To this end, the protection device needs to monitor the battery voltage, and when it reaches the battery overcharge voltage, it will activate the overcharge protection function and stop charging. Overdischarge protection: in order to prevent the overdischarge state of the lithium ion battery, when the voltage of the lithium ion battery is lower than the detection point of its overdischarge voltage, the overdischarge protection will be activated, the discharge will be stopped, and the battery will be kept in the standby mode of low static current. Overcurrent and short circuit protection: when the discharge current of lithium ion battery is too large or short circuit occurs, the protective device will activate the overcurrent protection function.

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