The 18650 numbers in the 18650 lithium battery represent the external dimensions: 18 represents the diameter of 18mm, 65 represents the length of 65mm, and 0 represents the cylindrical battery. It is a standard lithium-ion battery model set by the Japanese SONY company in order to save costs, called 18650 lithium battery.
The 18650 lithium battery pack usually consists of three parts: 18650 batteries, protection board (usually called PCBA) and shell structural parts. The best 18650 lithium battery pack should choose the best following three components:
1. Use high-quality 18650 batteries
The best 18650 lithium battery pack should be composed of first-line brand batteries, and the mainstream capacity ranges from 1800mAh to 3500mAh. The single battery has undergone a series of safety tests and performance tests. After years of quality evaluation, the following high-quality batteries are recommended:
18650 batteries of the world's top brands: SAMSUNG, PANASONIC, LG, SANYO, SONY
2. Multi-function protection circuit board (PCBA)
The core component of the lithium battery protection board is the protection IC. The main materials of the protection board are PCB, magnetic field effect tube (MOS tube), NTC, PTC, capacitor, resistor, diode, triode, etc.
Overcharge protection: When the voltage of a certain string of the battery pack is greater than (overvoltage) the maximum value, and the protection delay is reached, the IC controls the CMOS to turn off the charging circuit.
Over-discharge protection: When the voltage of a certain string of the battery pack is less than (under-voltage) the maximum value and the protection delay is reached, the IC controls the DMOS to turn off the discharge point loop.
Over-current and short-circuit protection: When the output current of the battery pack P+ and P- exceeds the over-current/short-circuit current value and reaches the over-current/short-circuit delay, the control circuit controls the discharge DMOS to turn off the discharge circuit and stop the discharge.
High and low temperature protection: When the temperature sensor reaches the temperature threshold and the protection delay is reached, the control circuit controls to turn off the charge and discharge MOS tube to stop charging and discharging.
The lithium battery protection board also has functions such as power detection, remaining capacity display, battery working status display, and communication remote control.
3. Shell structure
According to the needs of electrical appliances, design a matching shell structure, usually plastic shell, metal shell, simple PVC heat shrink and so on.
4. Superb lithium battery PACK technology
For the 18650 lithium battery pack, the superb PACK capability is very important. It is necessary to have advanced equipment, skilled technical workers, mature management mode, and rigorous production requirements to ensure that the 18650 lithium battery pack can be welded, tested, and There will be no omissions in important links such as aging and pre-shipment testing, and the best 18650 lithium battery pack will be produced.
How to choose a high-quality 18650 lithium battery?
Choose the 18650 lithium battery that is most suitable for you according to our electrical equipment, such as the appropriate brand, voltage, capacity, continuous discharge rate, battery life, etc. The most important thing is to choose a battery with high safety. Below we will start a detailed introduction one by one:
Regarding brands, there are internationally well-known brands such as Sanyo, Samsung, SONY, and LG that are more reliable.
Sanyo and LG focus on conventional applications, and their applications are mainly glare flashlights, power banks, and laptop batteries.
SONY specializes in high-current power. Take the VTC4 as an example, the discharge current can reach 30A, electronic cigarettes, toy airplanes, etc., can easily do it.
2. Nominal capacity
The nominal capacity of the 18650 battery is related to the endurance. The unit is "mAh". The higher the capacity, the stronger the endurance. For example, a 2800mAh battery can be continuously discharged for 2 hours at 1.4A.
3. Continuous discharge current (CDR)
Continuous discharge capacity is expressed by C number, continuous discharge current = continuous discharge capacity C number × capacity.
For example, the capacity of an 18650 battery is 2800mAh, and the continuous discharge capacity is 0.5C, then the continuous discharge current = 1.4A. Discharging over 1.4A for a long time will seriously affect the battery life, and there may be dangers such as overheating, burning, and explosion. .
5. Internal resistance
The internal resistance is the resistance of the battery itself. The smaller the internal resistance, the lower the consumption and the stronger the discharge capacity. The internal resistance parameter will generally be written on the battery introduction page. Please pay attention to it when you buy it. Try not to Buy batteries over 100mΩ.
To use multiple 18650 batteries in series, you must buy batteries of the same brand and model, otherwise batteries with large internal resistance and low capacity will become shortcomings.
Temperature is a major factor affecting the life of the 18650 lithium battery. The higher the temperature, the more the battery will age. The higher the temperature, the greater the internal damage of the battery.
7, pointed head and flat head
The 18650 lithium battery also has a flat tip and a pointed tip. As shown in the figure below, the positive pole on the left has a protruding tip, and the positive pole on the right without a protruding part is a flat tip.
Under normal circumstances, I recommend buying pointed batteries to ensure compatibility with more devices and uses. Usually the positive and negative poles of the flashlight are designed with springs, which can be extended and contracted, regardless of the pointed tip and flat tip batteries. But if the flat-head battery is used in series, the positive electrode of the flat-head cannot touch the negative electrode of another battery.
8. With protection board and without protection board
The pointed 18650 has a protective plate, and the flat 18650 does not have a protective plate.
The 18650 lithium battery with protection board is a few mm higher than the 18650 lithium battery without protection board, and the price is slightly more expensive, but it is safer and more versatile. The 18650 lithium battery with protection board can prevent the battery from over-discharge, which will cause over-discharge. Lithium batteries may generate heat, and may even burn or explode.
5. How to avoid buying fake 18650 lithium batteries?
When we buy 18650 lithium batteries, we will inevitably encounter many fake products on the market. How should we avoid buying fake and shoddy products?
1. Choose high-quality suppliers
2. Check the workmanship of the battery. The genuine lithium battery shell is made of special materials, which is very sturdy, and has a neat appearance, no extra burrs, a certain degree of roughness on the outer surface and a comfortable feel, and the inner surface feels smooth.
3. Pay attention to checking brand trademarks, product qualification certificates, inspection certificates, etc.
The lithium battery label adopts secondary printing technology. Under certain light, from the side, it is obvious that the color of the barcode part is darker than the rest.
4. The battery performance test must ensure that the battery performance passes the test.