What is an 18650 battery?
The 18650 battery is the precursor of lithium-ion batteries. It was established as a standard lithium-ion battery model by the Japanese company SONY to save costs. The “18” in 18650 stands for a diameter of 18mm, the “65” represents a length of 65mm, and the “0” indicates a cylindrical battery. Lithium-ion batteries are known for their advantages, including lightweight, high capacity, and no memory effect, making them widely used in many digital devices, despite their relatively higher price. Lithium-ion batteries have a high energy density, with a capacity 1.5 to 2 times greater than nickel-metal hydride batteries of the same weight, and they have a low self-discharge rate. Additionally, their lack of a significant “memory effect” and the absence of toxic substances are also important reasons for the widespread use of lithium-ion batteries. Furthermore, it’s important to note that lithium batteries are often labeled with “4.2V lithium battery,” “4.2V rechargeable lithium battery,” or similar markings in English on the outside of the battery to avoid mistaking nickel-cadmium or nickel-metal hydride batteries for lithium batteries when purchasing.
History of the 18650 Battery Cell
Cylindrical battery cells have the longest history, the most mature manufacturing processes, strong cell consistency, and relatively low costs. Sony introduced its first commercial battery in cylindrical form in 1991, naming the battery model “18650,” where 18 represents the diameter of 18 millimeters, 65 represents a length of 65 millimeters, and 0 indicates a cylindrical cell. The 18650 battery quickly became an industry standard and found widespread use in the consumer electronics sector, remaining popular and in use to this day.
Advantages of 18650 Battery Cells
(1) Large Capacity
18650 lithium batteries typically have a capacity ranging from 1200mAh to 3600mAh, while regular batteries have a capacity of only around 800mAh. When combined into an 18650 lithium battery pack, it’s easy to surpass 5000mAh.
(2) Long Lifespan
18650 lithium batteries have a long lifespan, with a normal usage cycle life of over 500 cycles, which is more than twice that of regular batteries.
(3) High Safety Performance
18650 lithium batteries offer high safety performance, as their positive and negative terminals are separated to prevent short-circuit incidents. The risk of short-circuit is minimized. Additionally, protective circuit boards can be added to prevent overcharging and over-discharging, further extending the battery’s lifespan.
(4) High Voltage
18650 lithium batteries typically have voltages of 3.6V, 3.8V, and 4.2V, which is much higher than the 1.2V voltage of nickel-cadmium and nickel-metal hydride batteries.
(5) No Memory Effect
There is no need to completely discharge the battery before recharging, making them convenient to use.
(6) Low Internal Resistance
Polymer cells have lower internal resistance compared to typical liquid cells. Domestic polymer cells can even achieve internal resistance of 35mΩ or less, significantly reducing self-discharge and extending the standby time of devices like smartphones. These high-discharge polymer lithium batteries are ideal for remote control models and have the potential to replace nickel-metal hydride batteries.
(7) Can be Connected in Series or Parallel to Form 18650 Battery Packs
(8) Wide Range of Applications
18650 batteries are used in various electronic devices, including laptops, two-way radios, portable DVD players, instruments, audio equipment, remote-controlled models, toys, cameras, digital cameras, and more.
·Types of 18650 battery cells
The charging and discharging principle of a 18650 lithium-ion battery:
The working principle of a lithium-ion battery refers to its charging and discharging process. When the battery is charged, lithium ions are generated on the positive electrode of the battery. These generated lithium ions move through the electrolyte to the negative electrode. The negative electrode, typically made of layered carbon structures, has many micropores. The lithium ions that reach the negative electrode are inserted into the micropores of the carbon layer. The more lithium ions are inserted, the higher the charging capacity.
Similarly, when the battery is discharged (i.e., during the usage of the battery), the lithium ions embedded in the negative electrode’s carbon layer are released and move back to the positive electrode. The more lithium ions return to the positive electrode, the higher the discharging capacity. Typically, the battery capacity refers to the discharging capacity.
It is evident that during the charging and discharging process of a lithium-ion battery, lithium ions move from the positive electrode → negative electrode → positive electrode. If we metaphorically compare a lithium-ion battery to a rocking chair, with the two ends of the rocking chair representing the two poles of the battery, then the lithium ions act like skilled athletes running back and forth between the two ends of the rocking chair. This is why experts have given lithium-ion batteries the endearing name “rocking-chair batteries.”
Precautions for Using 18650 Battery Cells:
In terms of storage, the temperature range for 18650 battery cells is 0°C to 60°C, the operating temperature is -20°C to 50°C, and the optimal operating temperature is 20°C to 40°C. A temperature of 60 degrees is the limit to ensure battery life, as high temperatures can reduce its lifespan, and temperatures exceeding 100 degrees can pose a danger, with combustion or explosion becoming possible, typically occurring around 130 degrees.
When charging for the first time, it’s advisable to charge during the daytime. Charging at night can lead to overcharging and potential battery damage. Charging during the day allows for better control of the charging time, and it’s essential to pay attention to the duration.
It’s best to opt for daytime charging and avoid charging 18650 lithium-ion batteries overnight. Ensure the charging time is well-managed and ideally doesn’t exceed 8 hours. Overcharging can shorten the lifespan of 18650 lithium-ion batteries and may result in excessive negative voltage.
What is the lifespan of 18650 battery cells?
18650 batteries are known for their large capacity, long lifespan, and high safety performance. Generally, 3.7V 18650 lithium-ion batteries have a cycling lifespan of around 500 to 1000 cycles, while 3.2V 18650 batteries typically have a lifespan of 2000 cycles or more.
How to charge 18650 battery cells?
18650 lithium-ion battery cells should be charged at a temperature between 0°C and 45°C. Their safe operating voltage range is 2.8V to 4.2V. Going below or above this voltage range can make the lithium ions in the battery very unstable and may lead to accidents. To ensure the battery remains within the safe range, it’s important to use dedicated chargers specifically designed for 18650 batteries. These chargers automatically adjust the charging mode based on the battery’s current condition.
How to safely dispose of 18650 battery cells:
As electronic products become more widespread and are continually replaced at a rapid pace, a significant amount of used batteries are generated, including a large number of 18650 batteries. Properly recycling and disposing of 18650 batteries is crucial.
Do not dispose of them carelessly:
Used 18650 batteries should be handled properly and should not be casually thrown into trash bins or left in the natural environment. These batteries contain small amounts of hazardous substances, and incorrect disposal can potentially pollute soil, water sources, and the air.
Separate for recycling:
Different types of batteries may have different components and require different recycling processes. Make sure to separate 18650 batteries from other types of batteries to ensure proper handling and recycling.
Utilize professional recycling channels:
To ensure the correct disposal and recycling of used 18650 batteries, it is recommended to entrust them to professional recycling channels. Some cities and regions have designated recycling centers or collection bins for used batteries. Additionally, you can utilize recycling programs offered by electronic product manufacturers or battery manufacturers.
Prevent damage:
When recycling used 18650 batteries, try to avoid damaging the battery casing. Damaged casings could lead to the leakage of hazardous materials from within the battery, increasing the risk of environmental pollution. Therefore, during transportation and storage of used batteries, try to prevent contact with sharp objects or metal materials.
Avoid short-circuits:
Used 18650 batteries may retain some charge, so it’s essential to take precautions to avoid short-circuits during the recycling process. Short-circuits can lead to severe consequences such as overheating, explosions, or even fires. Before recycling, you can use tape or other insulating materials to seal the positive and negative terminals of the battery to prevent short-circuits.
In conclusion, proper disposal and recycling of used 18650 batteries are essential for environmental protection and human health. Each of us has a responsibility to deliver used batteries to professional recycling channels to ensure they are handled and recycled correctly.
Factors to consider when choosing the best 18650 lithium-ion battery:
Capacity: The battery’s capacity determines the amount of energy it can store. Higher capacity batteries typically have a longer lifespan compared to lower capacity ones.
Voltage: The battery’s voltage determines its power output. Most 18650 batteries have a voltage of 3.7 volts, but some batteries may have higher or lower voltages.
Brand and Quality: Choosing a reputable brand and high-quality batteries is essential to ensure safety and reliability.
Protection Circuit: Some 18650 batteries come with a protection circuit that can prevent overcharging, over-discharging, and short circuits. This enhances the battery’s safety and lifespan.
Price: Cheaper batteries may have lower quality and may not be as durable or safe as more expensive options.
Intended Use: Consider the battery’s intended use, as some batteries are better suited for high-drain devices like flashlights, while others may be more suitable for low-drain devices like remote controls.
