Lithium-ion batteries are widely used due to their advantages such as light weight, large capacity, and no memory effect. Many digital devices use lithium-ion batteries as their power source, despite their relatively high price. Lithium-ion batteries have a very high energy density, with a capacity 1.5 to 2 times that of nickel-metal hydride batteries of the same weight, and a very low self-discharge rate. Furthermore, the near absence of a "memory effect" and the absence of toxic substances are also important reasons for their widespread use. There are many types of lithium batteries; this article compares and contrasts 18650 and 26650 lithium batteries.
I. 18650 Lithium Battery
In the 18650 lithium battery designation, 18 indicates a diameter of 18mm, 65 indicates a length of 65mm, and 0 indicates a cylindrical shape. 18650 batteries are generally more commonly used in industrial applications and less so in consumer use, primarily found in laptop batteries and high-end flashlights.
(I) Advantages of 18650 Lithium Batteries
1. Large capacity: The capacity of 18650 lithium batteries is generally between 1200mAh and 3600mAh, while the capacity of ordinary batteries is only around 800mAh. If they are combined into an 18650 lithium battery pack, the capacity of the 18650 lithium battery pack can easily exceed 5000mAh.
2. Long lifespan: 18650 lithium batteries have a very long lifespan, with a cycle life of more than 500 cycles under normal use, which is more than twice that of ordinary batteries.
3. High Safety Performance: 18650 lithium batteries boast high safety performance, being non-explosive and non-flammable; non-toxic and pollution-free, RoHS certified; possessing comprehensive safety features, with a cycle life exceeding 500 cycles; excellent high-temperature resistance, achieving 100% discharge efficiency at 65 degrees Celsius. To prevent short circuits, the positive and negative terminals of the 18650 lithium battery are separate. Therefore, the possibility of a short circuit is minimized. A protection board can be added to prevent overcharging and over-discharging, further extending the battery's lifespan.
4. High voltage: The voltage of 18650 lithium batteries is generally 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 remaining power before charging, making it convenient to use.
6. Low internal resistance: Polymer cells have lower internal resistance than ordinary liquid cells. Domestically produced polymer cells can even achieve an internal resistance below 35mΩ, significantly reducing battery self-discharge and extending phone standby time, fully meeting international standards. This type of polymer lithium battery, which supports high discharge current, is an ideal choice for remote control models and is the most promising replacement for nickel-metal hydride batteries.
7. Can be connected in series or parallel to form an 18650 lithium battery pack.
8. Wide range of applications: laptops, walkie-talkies, portable DVDs, instruments, audio equipment, model airplanes, toys, video cameras, digital cameras and other electronic devices.
(II) Disadvantages of 18650 Lithium Batteries
The biggest drawback of 18650 lithium batteries is their fixed size, which makes them difficult to position in some laptops or other products. However, this drawback can also be seen as an advantage, as it's a disadvantage compared to other lithium batteries like polymer lithium batteries, which offer customization and size variations. Conversely, it becomes an advantage for products with specific battery specifications.
18650 lithium batteries are prone to short circuits or explosions, especially compared to polymer lithium batteries. However, this drawback is less pronounced compared to regular batteries.
All 18650 lithium battery manufacturers require protection circuits to prevent overcharging and subsequent discharge. This is essential for lithium batteries, and it's a common drawback because they primarily use lithium cobalt oxide, which cannot withstand high current discharges, resulting in lower safety.
The production conditions for 18650 lithium batteries are demanding. Compared to general battery production, 18650 lithium batteries have much higher requirements for production conditions, which undoubtedly increases production costs.
II. 26650 Lithium Battery
26650 lithium batteries are a type of cylindrical lithium battery. They are used in power tools, lighting, wind and solar energy storage, electric vehicles, toys, instruments, UPS backup power supplies, communication equipment, medical equipment, and military applications. The model designation is: 26650, meaning a cylindrical battery with a diameter of 26mm and a length of 65mm.
(I) General Electrical Performance of 26650 Lithium Batteries
Cycling performance: 2000 cycles (1C charge/1C discharge, capacity retention ≥80%, 100% DOD)
Maximum continuous discharge current: 9.6A
Pulse discharge current: 15A, 5s
Operating temperature: Charging: 0°C~55°C; Discharging: -20°C~60°C
Storage temperature: -20°C to 45°C
Battery weight: 86g (approx.)
III. Which is better, 18650 lithium batteries or 26650 lithium batteries?
1. Battery volume comparison: The volume of 26650 lithium battery is larger than that of 18650 lithium battery. Their cell height is the same, but the cell diameter is different. The cell diameter of 26650 lithium battery is 26mm, while that of 18650 lithium battery is 18mm.
2. Battery capacity comparison: Under the same battery materials, the capacity of 26650 batteries is larger than that of 18650 batteries. Assuming that both use ternary materials, the capacity of 26650 batteries is generally around 5200mAh, while the capacity of 18650 batteries is mostly around 2600mAh.
3. Comparison of application environments: 18650 lithium batteries are widely used in lighting fixtures, industrial supporting lithium battery packs, power tool batteries, electric bicycle batteries, and power lithium battery packs, while 26650 lithium batteries are widely used in integrated solar street light lithium battery packs, energy storage stations, and solar energy storage batteries.
