18650 lithium battery

The 18650 is the originator of the lithium ion battery -- a standard lithium ion battery model set by the Japanese SONY company in order to save costs, of which 18 represents a diameter of 18mm, 65 represents a length of 65mm, and 0 represents a cylindrical battery.

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

Lithium Ion Battery (Li-ion, Lithium Ion Battery): Lithium-ion batteries are widely used because of their light weight, large capacity, and no memory effect. Many digital devices use lithium-ion batteries as power supplies, despite their price. Relatively expensive. Lithium-ion batteries have a high energy density, and their capacity is 1.5 to 2 times that of nickel-hydrogen batteries of the same weight, and has a very low self-discharge rate. In addition, the lithium-ion battery has almost no "memory effect" and does not contain toxic substances, which is also an important reason for its wide application. In addition, please note that the outside of the lithium battery is generally marked with English 4.2V lithiumion battery (lithium battery) or 4.2V lithium secondary battery (lithium secondary battery), 4.2V lithiumion rechargeable battery (charged lithium battery), so users must buy the battery must Look at the signs on the exterior of the battery block to prevent the cadmium nickel and nickel hydride batteries from being mistaken for lithium batteries because they do not see the battery type.

Lithium battery standard 3.7 v or 4.2 is the same, but the manufacturer has marked the difference. 3.7V refers to the platform voltage (ie typical voltage) discharged during battery use, and 4.2 volt refers to the voltage when fully charged . Common rechargeable 18650 lithium battery, the voltage is 3.6 or 3.7 v, when fully charged is 4.2 v, which has little to do with the power (capacity), 18650 battery mainstream capacity from 1800 mah to 2600 mah, (18650 power The battery capacity is more than 2200 ~ 2600 mah), the mainstream capacity is even above the standard 3500 or 4000 mah (remind everyone, the domestically produced batteries above the nominal 3350 mah are likely to be fake, the current domestic quantity The maximum capacity produced is 3350 mah.).

It is generally considered that the lithium battery's no-load voltage is less than 3.0 v and it is considered that the power is used up (the specific value needs to look at the threshold of the battery protection board, such as as low as 2.8 v, also 3.2 v). Most lithium battery discharges can not put the no-load voltage below 3.2 v, otherwise excessive discharge will damage the battery (usually the lithium battery on the market is basically used with a protective plate, so excessive discharge will also cause the protection board to detect To the battery, it is impossible to charge the battery.) 4.2V is the highest limit voltage for battery charging. It is generally considered that charging the lithium battery with no-load voltage to 4.2 v is considered to be full. During battery charging, the battery voltage is 3.7 v. Gradually rising to 4.2 v, lithium battery charging can not charge the no-load voltage to 4.2 v or more, otherwise it will damage the battery, which is the special place of the lithium battery.

The 18650 battery life theory is cyclic charging 1000 times. Due to the large capacity per unit density, most of them are used in laptop batteries. In addition, the stability of the 18650 is very good at work. It is widely used in various electronic fields: it is often used in high-end glare flashlights. Power, wireless data transmitters, electric warm clothing, shoes, portable instrumentation, portable lighting equipment, portable printers, industrial equipment, medical equipment, etc.

The 18650 means 18 mm in diameter and 65 mm in length. The model number of the No. 5 battery is 14,500, 14 mm in diameter and 50 mm in length. Generally, the 18650 battery is used in the industry, and there are few civilians. The common ones are used in laptop batteries and high-end flashlights.

The 18650 is just the size of the battery. It can be divided according to the type of battery. The lithium ion is 18650 years, the lithium iron phosphate is 18650 years, the nickel hydrogen is 18650 (rare), and the common 18650 is lithium ion.

Charge and discharge principle

The working principle of lithium-ion battery refers to its charging and discharging principle. When the battery is charged, lithium ions are generated on the positive electrode of the battery, and the generated lithium ions move to the negative electrode through the electrolyte. The carbon as the negative electrode has a layered structure, and it has many micropores. The lithium ions reaching the negative electrode are embedded in the micropores of the carbon layer, and the more lithium ions are embedded, the higher the charging capacity.

By the same token, when the battery is discharged (the process we use the battery), the lithium ions embedded in the carbon layer of the negative electrode come out and move back to the positive electrode. The more lithium ions return to the positive electrode, the higher the discharge capacity. What we usually call battery capacity refers to the discharge capacity.

It is not difficult to see that during the charging and discharging process of the lithium ion battery, the lithium ion is in a state of motion from the positive electrode to the negative electrode to the positive electrode. If we compare the lithium-ion battery to a rocking chair, the two ends of the rocking chair are the two poles of the battery, and the lithium ion is like an excellent sportsman, running back and forth at both ends of the rocking chair. Therefore, the experts gave the lithium-ion battery a cute name rocking chair battery.

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 4.2 v, the charger will charge at a constant current. The second stage is the constant voltage charging phase. When the battery voltage reaches 4.2 v, due to the characteristics of the lithium battery, if the voltage is high, it will be damaged. The charger will fix the voltage at 4.2 v, and the charging current will gradually decrease. When it is reduced to a certain value (generally 1/10 set current), the charging circuit is cut off, the charging completion indicator lights up, and charging is completed.

Excessive charging and discharging of lithium-ion batteries can cause permanent damage to the positive and negative electrodes. Over-discharge leads to collapse of the negative carbon sheet structure, and collapse can cause lithium ions to be inserted during charging; excessive charging causes excessive lithium ions to be embedded in the negative carbon structure, and some of the lithium ions can no longer be released.

Some chargers are implemented using inexpensive solutions, which are not good enough in control accuracy, which may cause abnormal battery charging and even damage the battery. When purchasing the charger, try to choose the 18650 lithium-ion battery charger of the big brand, the quality and after-sales guarantee, and extend the service life of the battery. The brand-assured 18650 lithium-ion battery charger has four protections: short circuit protection, over current protection, over voltage protection, and battery reverse connection protection. Overcharge protection: When the charger overcharges the lithium ion battery, it is necessary to terminate the charging state in order to prevent the internal pressure from rising due to temperature rise. To this end, the protection device needs to monitor the battery voltage. When it reaches the battery overcharge voltage, it activates the overcharge protection function and stops charging. Over-discharge protection: In order to prevent the over-discharge state of the lithium-ion battery, when the lithium-ion battery voltage is lower than its over-discharge voltage detection point, the over-discharge protection is activated, the discharge is stopped, and the battery is kept in the standby mode of low quiescent current. Overcurrent and short circuit protection: When the discharge current of the lithium ion battery is too large or a short circuit occurs, the protection device activates the overcurrent protection function.

The nominal voltage of a single section is generally: 3.6 v or 3.7 v

The charging voltage is generally: 4.20 v (lithium cobaltate is 4.2 v - 4.3 v)

The minimum discharge termination voltage is generally 2.75 v. Below this voltage, the battery capacity is seriously degraded and even scrapped.

Maximum charge termination voltage: 4.20 v

Diameter: 18±0.2 mm

Height: 65±2.0 mm

Capacity: 1000 mah or more, regular capacity is 2200 mah - 3200 mah, the current 18650 battery capacity is the highest is LG, can achieve 3600 mah, but the price is not low.

1, the capacity of large 18650 lithium battery capacity is generally between 1200 mah ~ 3600 mah, and the general battery capacity is only about 800 mah, if the combination of 18650 to lithium battery pack, then 18650 lithium battery pack can be easily broken 5000 mah.

2, long life 18650 lithium battery has a long service life, the normal life cycle can reach more than 500 times, more than twice the average battery.

3, high safety performance 18650 lithium battery safety performance, no explosion, no burning; non-toxic, non-polluting, after RoHS trademark certification; all kinds of safety performance in one go, the number of cycles is greater than 500 times; high temperature performance, 65 degrees The discharge efficiency is up to 100%. In order to prevent battery short circuit, the positive and negative poles of the 18650 lithium battery are separated, so the possibility of short circuit has been reduced to the extreme. A protective plate can be added to prevent the battery from overcharging and over-discharging, which also extends the battery life.

4, the voltage of the high voltage 18650 lithium battery is generally 3.6 v, 3.8 v and 4.2 v, much higher than the 1.2 v voltage of nickel-cadmium and nickel-hydrogen batteries.

5, no memory effect It is not necessary to empty the remaining power before charging, it is convenient to use.

6. The internal resistance is small: the internal resistance of the polymer battery is smaller than that of the general liquid battery. The internal resistance of the domestic polymer battery can even be less than 35 mΩ, which greatly reduces the self-consumption of the battery and prolongs the mobile phone. Standby time can fully reach the level of international standards. This polymer lithium battery that supports large discharge currents is an ideal choice for remote control models and is the most promising alternative to nickel-metal hydride batteries.

7, can be combined in series or parallel to form a 18650 lithium battery pack

8, a wide range of use laptop, walkie-talkie, portable DVD, instrumentation, audio equipment, aircraft models, toys, cameras, digital cameras and other electronic equipment

Disadvantage

The biggest disadvantage of the 18650 lithium battery is that his volume has been fixed. It is not very well positioned when it is installed in some notebooks or some products. Of course, this shortcoming can also be said to be an advantage. This is a lithium battery equivalent to other polymer lithium batteries. This is a disadvantage in terms of customizable and transformable size. It is an advantage over some products with specified battery specifications.

The 18650 lithium battery is prone to short circuit or explosion, and it is also relative to the polymer lithium battery. If it is relatively normal, this disadvantage is not so obvious.

18650 lithium battery production needs to have a protection circuit to prevent the battery from being overcharged and causing discharge. Of course, this is a must for lithium batteries, which is also a disadvantage of lithium batteries, because the materials used in lithium batteries are basically lithium cobalt oxide materials, and lithium batteries of lithium cobalt oxide materials can not discharge, safety. Poor.

The production conditions of the 18650 lithium battery are high. Compared with the general battery production, the 18650 lithium battery has high requirements on the production conditions, which undoubtedly increases the production cost.

The page contains the contents of the machine translation.