How long is the general cycle life of 18650 lithium battery?
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2023/05/16 11:03:25
Now 3.7V 18650 general cycle life can reach 500~1000 times, 3.2V 18650 general life can reach more than 2000, of course, the premise is the regular manufacturer of qualified batteries, if it is defective or counterfeit batteries, life will be very short.
The 18650 is a standard lithium-ion battery model adopted by SONY Corporation of Japan, the originator of lithium-ion batteries, in order to save costs. 18 represents a diameter of 18mm, 65 represents a length of 65mm, and 0 represents a cylindrical battery.
The common 18650 battery is divided into lithium ion battery, lithium iron phosphate battery. Lithium ion battery voltage nominal voltage is 3.7v, charging cut-off voltage is 4.2v, lithium iron phosphate battery nominal voltage is 3.2V, charging cut-off voltage is 3.6v, capacity is usually 1200mAh-3350mAh, common capacity is 2200mAh-2600mAh.
Lithium-ion battery (Li-ion, LithiumIonBattery) : Lithium-ion battery has the advantages of light weight, large capacity, no memory effect, so it has been widely used -- many digital devices have adopted lithium-ion battery as a power supply, although its price is relatively expensive. The energy density of lithium ion battery is very high, its capacity is the same weight of nickel metal hydride battery 1.5~2 times, and has a very low self-discharge rate. In addition, lithium-ion batteries have almost no "memory effect" and no toxic substances, which are also important reasons for their widespread use. Also please note that the lithium battery external generally marked with English 4.2 Vlithiumionbattery (lithium battery) or 4.2 Vlithiumsecondarybattery (lithium secondary battery), 4.2 Vlithiumionrechargeablebattery (rechargeable lithium battery), Therefore, when purchasing batteries, users must see the signs on the surface of the battery block to prevent cadmium nickel and nickel-hydrogen batteries from being mistaken for lithium batteries because they do not see the battery type clearly. Lithium battery standard 3.7V or 4.2V is the same. It's just that the manufacturer labels it differently. 3.7V refers to the platform voltage (i.e., typical voltage) at which the battery is discharged during use, while 4.2 volts refers to the voltage at full charge. Common can be charged 18650 lithium battery, voltage is standard 3.6 or 3.7v, full of 4.2v, this is not related to the power (capacity), 18650 battery mainstream capacity from 1800mAh to 2600mAh, (18650 power battery capacity in more than 2200~2600mAh), The mainstream capacity even has the standard 3500 or 4000mAh above all have (remind you, in the market called 3350mAH above the domestic cell is likely to be false, the current domestic mass production of the maximum capacity of 3350mAh). .
It is generally believed that when the no-load voltage of the lithium battery is below 3.0V, the battery is considered to be used up (the specific value depends on the threshold value of the battery protection board, such as as low as 2.8V or 3.2V). Most lithium battery discharge can not put the no-load voltage to 3.2V below, otherwise excessive discharge will damage the battery (lithium battery on the general market is 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 limit voltage of battery charging, it is generally believed that the no-load voltage of lithium battery is charged to 4.2V, the battery charging process, the battery voltage in 3.7V gradually rises to 4.2V, lithium battery charging can not be charged to the no-load voltage above 4.2V, otherwise it will damage the battery, this is the special place of lithium battery.
The 18650 battery life is theoretical for 1000 cycles of charge. Due to the large capacity of the unit density, most of them are used in laptop batteries. In addition, because of the stable performance of 18650 in the work is very good, it is widely used in various electronic fields: often used in high-grade light flashlight, portable power supply, wireless data transmission device, electric thermal clothes, shoes, portable instruments, portable lighting equipment, Portable printers, industrial instruments, medical instruments, etc.
18650 means 18 millimeters in diameter and 65 millimeters in length. The number 5 battery model is 14500, 14 mm in diameter and 50 mm in length. Generally, 18650 batteries are used more in industry and less in civil use. It is common to use more batteries in notebooks and high-grade flashlights.
18650 is only the size of the battery model, according to the battery type can also be divided into lithium ion 18650, lithium iron phosphate 18650, nickel metal hydride 18650 (very rare), the common 18650 is lithium ion.
Charge and discharge principle
Lithium-ion batteries work on the principle of charge and discharge. When the battery is charged, lithium ions are generated on the positive side of the battery, and the resulting lithium ions travel through the electrolyte to the negative side. As a negative electrode, carbon has a layered structure with many micropores. Lithium ions arriving at the negative electrode will be embedded into the micropores of the carbon layer. The more lithium ions embedded, the higher the charging capacity.
Similarly, when a battery is discharged (which is what we do with batteries), the lithium ions embedded in the negative carbon layer escape and travel back to the positive electrode. The more lithium ions that return to the positive electrode, the higher the discharge capacity. What we usually refer to as battery capacity is discharge capacity.
It is not difficult to see that in the charging and discharging process of lithium ion battery, lithium ion is in a state of motion from positive to negative to positive. If we compare the lithium-ion battery to a rocking chair, the two ends of the rocking chair are the poles of the battery, and lithium ion is like an excellent athlete, running back and forth at both ends of the rocking chair. That's why experts have given lithium-ion batteries the cute name rocking chair batteries.
Charge and discharge process
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 be charged at a constant current. The second stage is the constant voltage charging stage, when the battery voltage reaches 4.2V, due to the characteristics of lithium battery, if the voltage is higher, it will be damaged, the charger will be fixed at 4.2V, charging current will gradually decrease, when the current decreases to a certain value (generally 1/10 setting current), cut off the charging circuit, charging completed indicator light, charging completed.
Overcharging and discharging lithium-ion batteries can cause permanent damage to the positive and negative electrodes. Excessive discharge leads to the collapse of the carbon lamellar structure of the negative electrode, and the collapse will cause that lithium ions cannot be inserted during the charging process. Overcharging causes too many lithium ions to be embedded in the negative carbon structure, and some of them can no longer be released.
Some chargers use cheap schemes to achieve, in the control accuracy is not good enough, easy to cause battery charging anomaly, and even damage the battery. When choosing a charger, try to choose a large brand of 18650 lithium ion battery charger, quality and after-sales guarantee, extend the battery life. Brand guarantee 18650 lithium-ion battery charger has four protection: short circuit protection, overcurrent protection, overvoltage protection, battery reverse connection protection function. Overcharge protection: When the charger overcharges the lithium-ion battery, the charging state should be terminated to prevent the internal pressure rise caused by rising temperature. Therefore, the protection device needs to monitor the battery voltage, when it reaches the battery overcharge voltage, that is, activate the overcharge protection function, 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 overdischarge voltage detection point, the overdischarge protection is activated, the discharge is terminated, and the battery is kept in standby mode of low static current. Overcurrent and short circuit protection: When the discharge current of the lithium-ion battery is too large or short circuit occurs, the protection device activates the overcurrent protection function.
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