How long is the general 18650 lithium battery cycle life? 2021-12-06
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2023/09/23 16:11:42
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 that the regular manufacturer of qualified batteries, if it is defective or counterfeit batteries, the life will be very short.
18650 is the originator of lithium-ion batteries - Japan's SONY company set a standard lithium-ion battery model in order to save costs, in which 18 indicates a diameter of 18mm, 65 indicates a length of 65mm, 0 indicates a cylindrical battery.
The common 18650 battery is divided into lithium-ion batteries and lithium iron phosphate batteries. Lithium-ion battery voltage is nominal voltage 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, the 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, and so has been widely used - many digital devices have used lithium-ion batteries as power supplies, although its price is relatively expensive. Lithium-ion batteries have a high energy density, and their capacity is 1.5 to 2 times that of nickel-metal hydride batteries of the same weight, and they have a very low self-discharge rate. In addition, lithium-ion batteries have almost no "memory effect" and do not contain toxic substances and other advantages are also important reasons for its wide application. 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. 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 4.2V refers to the voltage at full charge. Common rechargeable 18650 lithium battery, the voltage is standard 3.6 or 3.7v, fully charged when 4.2v, which has little to do with the power (capacity), 18650 battery mainstream capacity from 1800mAh to 2600mAh, (18650 power battery capacity is more than 2200~2600mAh), Mainstream capacity even has more than 3500 or 4000mAh (remind you, in the market nominal 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 the no-load voltage of the lithium battery is below 3.0V and that the electricity is used up (the specific value needs to see the threshold value of the battery protection board, such as as low as 2.8V and 3.2V). Most lithium battery discharge can not put the no-load voltage below 3.2V, otherwise excessive discharge will damage the battery (lithium batteries on the general market are basically used with a protection board, so excessive discharge will also lead to the protection board 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 lithium battery no-load voltage is charged to 4.2V, the battery charging process, the battery voltage at 3.7V gradually rises to 4.2V, lithium battery charging can not charge the no-load voltage to 4.2V or more, otherwise it will damage the battery, which is the special place of lithium battery.
18650 Battery life theory 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 stability of 18650 in the work is very good, widely used in major electronic fields: often used in high-grade light flashlight, portable power supply, wireless data transmission, electric warm 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 few in civilian use, and they are commonly used in notebook batteries and high-end flashlights.
18650 is only the size of the battery model, according to the type of battery can also be divided into lithium ion 18650, lithium iron phosphate 18650, nickel-metal hydride 18650 (rare), the common 18650 is lithium ion.
Charge and discharge principle
The working principle of a lithium-ion battery is its charge and discharge principle. When the battery is charged, lithium ions are generated on the positive electrode of the battery, and the generated lithium ions move through the electrolyte to the negative electrode. The carbon as the negative electrode has a layered structure, which has many microholes. The lithium ions that reach the negative electrode are embedded into the microholes of the carbon layer. The more lithium ions embedded, the higher the charging capacity.
Similarly, when a battery is discharged (which is the process we use batteries), the 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. What we usually call the battery capacity refers to the discharge capacity.
It is not difficult to see that in the charging and discharging process of lithium-ion batteries, lithium ions are 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 the lithium ion is like an excellent athlete, running back and forth at both ends of the rocking chair. So, experts have given lithium-ion batteries a lovely 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 charge 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 batteries, if the voltage is higher, it will be damaged, the charger will fix the voltage at 4.2V, the charging current will gradually decrease, when the current is reduced to a certain value (generally 1/10 setting current), cut off the charging circuit, the charging completion 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 lamella structure of the negative electrode, and the collapse will cause the lithium ion cannot be inserted during the charging process. Overcharging causes too many lithium ions to be embedded in the negative carbon structure, and some of the lithium ions can no longer be released.
Some chargers use cheap schemes, which are not good enough in control accuracy, easy to cause battery charging abnormalities, and even damage the battery. When purchasing a charger, try to choose a large brand of 18650 lithium-ion battery charger, quality and after-sales guarantee, extend the service life of the battery. The brand guaranteed 18650 lithium-ion battery charger has four protection functions: short circuit protection, overcurrent protection, overvoltage protection, battery reverse connection protection. Overcharge protection: When the charger overcharges the lithium-ion battery, in order to prevent the internal pressure rise caused by the rise in temperature, the charging state needs to be terminated. To this end, the protection device needs to monitor the battery voltage, and when it reaches the battery overcharge voltage, it activates the overcharge protection function and stops 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 its overdischarge voltage detection point, the overdischarge protection is activated, the discharge is terminated, and the battery is kept in the 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 will activate the overcurrent protection function.
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