18650 is the originator of lithium batteries - Japan's SONY company in order to save costs and set a standard lithium battery models
18650 type lithium batteries are more commonly used in electronic products lithium-ion batteries, often used as a battery cell in the laptop computer battery. The definition of its model law: such as 18650 type, that is, the diameter of the battery is 18mm, the length of 65mm, cylindrical type of batteries
Common 18650 batteries are divided into lithium batteries, lithium iron phosphate ion batteries. Lithium battery voltage is 3.7v nominal voltage, charging cut-off voltage is 4.2v, lithium iron phosphate ion battery nominal voltage is 3.2V, charging cut-off voltage is 3.6v, capacity is usually 1200mAh-3350mAh, common capacity is 2200mAh-2600mAh.
18650 is a type of lithium-ion battery, similar to dry cell battery No. 7, No. 5, No. 1 and so on.
Lithium batteries use a liquid electrolyte, while lithium polymer batteries use a solid polymer electrolyte instead, which can be solid or semi-solid (gel-like).
So Li-Polymer batteries come in a variety of shapes and can be customized. Whereas 18650 and the like require a metal casing, but are better value for money compared to polymer LiPo.
Some people say that 18650 will explode, in fact, now 18650 batteries are equipped with a safety valve at the top, when the battery internal pressure is too large, its top safety valve will automatically pop up to play the role of pressure reduction. However, when the safety valve pops out, the lithium ions leaking out of the battery will still catch fire due to contact with oxygen in the air.
TeslaModelS uses 8000 18650 batteries, about the importance of replaceability and safety, even if a single battery explosion, but only 1/8000 sprouting explosions, even if the fire, or better than a large polymer lithium, but the disadvantage is that the battery pack is too heavy.
Type difference
Lithium-ion battery labeled 3.7V or 4.2V are the same. Only the processor labeling is not the same themselves. 3.7V refers to the platform voltage of the battery discharge during use (i.e., the typical voltage), while 4.2 volts refers to the voltage when charging a full charge. Common rechargeable 18650 lithium-ion batteries, the voltage is labeled 3.6 or 3.7v, the ocean overflow of electricity is 4.2v, which has little to do with the amount of power (capacity), 18650 batteries mainstream capacity from 1800mAh to 2600mAh, (18650 power batteries capacity is more in the 2200 ~ 3600mAh), the mainstream capacity and even have a standard 3500 or 4000mAh or more are available.
It is generally believed that the unloaded voltage of lithium-ion batteries to 3.0V or less is considered to be exhausted (exhaustive value depends on the threshold value of the battery protection board, for example, there are as low as 2.8V, there are also 3.2V). Most of the lithium-ion battery discharge can not be put into the no-load voltage below 3.2V, otherwise over-discharge will damage the battery (general market lithium-ion batteries are basically used with a protection board, so over-discharge will also lead to the protection board can not test the battery, so that the battery can not be recharged). 4.2V is the highest limit of the battery charging voltage, lithium-ion batteries are generally considered to be the unloaded voltage to 4.2V, it is considered to be the electric battery is exhausted. 4.2V is considered to be overflowing, battery charging process, the battery's voltage at 3.7V gradually rose to 4.2V, lithium-ion battery charging can not be charged to the unloaded voltage of more than 4.2V, otherwise it will also damage the battery, which is a special place of lithium-ion batteries.
Usage
The theory of 18650 battery life is 1000 times of cycle charging. Because the capacity of unit density is very large, so most of them are used for laptop batteries, in addition to 18650 lithium-ion batteries, because 18650 in the work of the stability of the performance is very good, widely used in the major electronic categories: commonly used in high-grade flashlight flashlight, portable power supply, wireless data transmitters, electric warm clothing, shoes, portable instruments, portable lighting equipment, portable printers, industrial instruments, medical instruments and so on. instruments, medical instruments and so on.
After 30 years of development, 18650 battery preparation process has been very mature, in addition to the performance has been greatly improved, its safety is also very perfect. In order to avoid the explosion of the sealed metal shell, 18650 batteries are now equipped with a safety valve on the top of the battery, the safety valve is the standard of each 18650 battery, but also the most important one explosion-proof barrier. When the internal pressure of the battery is too large, the top safety valve will be opened to exhaust and depressurize to avoid explosion. However, when the safety valve is open, the chemical substances leaking out of the battery will have a chemical reaction with the oxygen in the air under high temperature conditions, and a fire may still occur. In addition, some of the 18650 batteries now also comes with a protection plate, with overcharge and overdischarge and short-circuit protection, etc., the safety performance is very high.
