18650 batteries are cylindrical batteries with nominal voltage in the range of 3.2V to 3.7V. With respect to shape, these batteries are similar to widely used AA batteries but tip shape of AA battery is mostly replaced with flat tip and size is slightly bigger. Cylinder of 18650 battery has a diameter of 18mm and a length of 65mm. Their capacity lies between 1800mAh and 3500mAh. BMS is integrated with these batteries most of the times to make them work safely. Mostly, these batteries are a type of rechargeable lithium-ion batteries having lithium iron phosphate (LFP) or any other chemistry within this group.
This article covers electrical and mechanical specifications of 18650 battery, various chemistry options for the battery, and its major applications. As AA type battery is very common so we will be presenting a section-wise comparison between AA and 18650 batteries so a beginner could get better understanding about its performance and characteristics. Finally, techniques and tips to prolong 18650 battery life will be discussed to help beginners extend 18650 battery life and make best use of their money.
Electrical, Mechanical, and other Specifications of 18650 Battery
18650 Battery Voltage
18650 batteries are available with nominal voltage ranging between 3.2 and 3.7V. Anyhow, maximum voltage limit for this battery goes up to 4.2V. If we compare this with an AA cell which has 1.2 to 1.5V nominal voltage, we can say that 18650 batteries have quite higher voltage output making them suitable for high-power devices.
18650 Battery Capacity
Capacity is another important electrical parameter for batteries as it indicates the duration for which battery can keep some device running. Capacity of an 18650 battery lies between 1800 and 3500mAh. On the other hand, AA battery has wide capacity range available, lying between 600mAh and 2700mAh depending upon the chemistry. Figures regarding capacity indicate that 18650 battery can store more energy and power a device for longer period.
18650 Battery Chemistry and Rechargeability
With extensive use of battery cells, their rechargeability feature has become a highly considerable aspect during battery selection process. Rechargeability feature of a battery depends upon its chemistry. 18650 battery comes in various chemistries including Lithium-Ion (preferably Lithium Cobalt Oxide and Lithium Iron Phosphate), Lithium polymer, and Nickle Metal Hydride (NiMH). All mentioned chemistries are rechargeable and so all 18650 batteries are rechargeable. On the other hand, AA batteries are for one-time use and not rechargeable.
Dimensions and Weight of 18650 Battery
Size of 18650 battery is slightly larger than AA batteries, hidden in its own name. 18 in 18650 indicates 18mm diameter of the battery. 65 in 18650 indicates 65mm length of battery. ‘0’ in the end of 18650 indicates cylindrical shape of the battery. In comparison, AA battery is slightly smaller with 14.5mm diameter, and 50.5mm length.
The way, dimensions are fixed for 18650 batteries, weight is not fixed. Weight of 18650 battery depends upon its chemistry, specific model, and manufacturer. It roughly ranges between 40 and 50 grams. For example, an 18650 battery with 2600mAh capacity and lithium ion chemistry weighs around 43 grams.
Discharge Rate for 18650 Battery
Discharge rate or ‘C-rating’ of a battery depicts the amount of current a battery can deliver to power a device. This, indirectly, determines discharge time and size of device being powered. Typical discharge rate of 18650 battery is 0.25C. 18650 batteries are available in high-drain variants also which are capable of delivering high current making them suitable for high-drain applications like flashlights, electronics, EVs, and power tools.
Other Performance Characteristics of 18650 Battery
Voltage, capacity, and thermal management are primary performance parameters which are discussed already. In this section, we will consider other performance parameters like life cycles, storage life and memory effect on 18650 batteries.
Life Cycle of 18650 Batteries
Life cycles of 18650 batteries typically range between 300 and 500 charge-discharge cycles. Batteries, which operate in high drain mode, experience significant reduction in life cycles. For example, a high-drain 18650 battery could be left with 200 cycles. And if a user pushes the battery to maximum limit for discharge current, then life cycles might go down to 50 only.
Memory Effect of 18650 Battery
Another attractive feature of 18650 type battery is having no memory effect. Memory effect also depends upon chemistry. Most chemistries of 18650 batteries specially lithium base chemistries have no memory effect. This feature gives users liberty to start using battery anytime without full charge.
Storage Life for 18650 Battery
Apart from life cycles, storage life of battery is another important aspect which helps users and prospective buyers decide if they can keep their power storage cell for long period of time without use or not. Storage life of a battery also depends upon chemistry. A lithium-ion 18650 battery can be stored for up to 10 years without losing its capacity substantially, if stored at ~3.7V.
Applications for 18650 Batteries
Above discussion shows that 18650 batteries have several attractive features like long cycle life, high discharge rate, high capacity, no memory effect, and good storage life without loss of capacity. Here, we will state different applications of 18650 type batteries while relating them with different operational characteristics.
- High charge and discharge rates, low weight, and long life cycle of 18650 batteries make these batteries suitable for electric powertrains specifically for electric motorcycles.such as the Xiaomi Mi Electric Scooter, which uses 18650 lithium-ion batteries for reliable performance.
- Owing to high discharge rate, high output voltage, and good capacity, 18650 batteries can provide instant high power making them a good choice for flashlights, and other lighting equipment.
- Power toolsg. electric drills, electric screwdrivers need compact, high capacity, and portable power supply. Respective features of 18650 battery cells make these batteries suitable for power tools.
- 18650 batteries are also used as battery energy storage systems for solar energy.such as the Tesla Powerwall, providing reliable power for homes and small businesses.
- In industries and warehouses, 18650 batteries are used in robots and drones to perform repeated tasks and monitor sites, thanks to their reliability, long cycle life, and high capacity.
- In electronic gadgets like laptops, 18650 battery cells can be used to form battery packs.
Prolonging lifespan of 18650 battery
For any user, specifically beginners and environmental enthusiasts, it is quite important to know the ways to prolong their battery life. As it brings economic benefits like reduced replacement costs, predictable and dependable operation, increased uptime and productivity, and higher energy efficiency. Extending battery life has environmental benefits also as less batteries mean resource conservation, reduced waste and pollution, and lower carbon footprint. Considering numerous benefits, tips to prolong lifespan of 18650 battery. are discussed.
Safe Charging Practices
Good charging practices are key to prolong life of any kind of battery including 18650 batteries. You must use charger designed specifically for concerned battery depending upon chemistry and recommended by manufacturer. User shall avoid leaving battery connected with charger for too long so battery doesn’t overcharge. This will also ensure that optimal voltage is maintained. Furthermore, one can invest in smart chargers to regulate and monitor charging process.
Optimal Storage of 18650 Battery
Ambient temperature during storage and operation of batteries impacts their lifetime significantly. It is good to store batteries at moderate temperature ranging between 20 and 25 degrees Celsius. While storing battery, if you expect that storage period would be extended, then try storing your battery partially charged (around 50%). Fully depleted or fully charged batteries would get affected negatively during storage.
Good Usage Conditions
Regarding usage of 18650 batteries, there are many ways to improve battery lifespan. Batteries which experience high discharge rates, are more likely to lose their life cycles as discussed above. So, user must ensure that 18650 battery is discharged at moderate rates. Moreover, deep discharge shall be avoided during discharging phase.
Avoiding Physical Damage and Appropriate Cleaning
Lifespan of 18650 battery is extended significantly if a user keeps batteries in a safe manner to keep them from getting physically damaged. Moreover, dust and other residues from environment get settled on battery terminals. Users must clean terminals with cloth regularly to prolong one’s battery life.
结论
18650 battery cells are available in various chemistries including Lithium-ion, lithium polymer, and Nickle metal hydride (NiMH). Their rechargeability feature paired with good capacity, ability to provide high drain currents, low discharge rates, long storage life, and extended life cycles makes these batteries valuable for many applications including flashlights, robots, and electric powertrains. We have also discussed ways to prolong 18650 battery life to help a beginner understand his/her battery requirements well.
