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18650 Lithium-ion Battery

18650 lithium battery

Today we will introduce the 18650 lithium-ion battery.

What is 18650 lithium-ion battery

The 18650 battery is a lithium-ion battery with a size of 18mm x 65mm, which is slightly larger than the AA battery. They have excellent capacity and discharge rate, so they are often used in flashlights, laptops and high drainage devices. 18650 has two types of flat and push-button style, usually with 300-500 charging cycles.

Most 18650 batteries will last between 300 and 500 charge cycles, but battery life can be greatly extended if charged regularly before fully discharged. All batteries will degrade over time, but depending on the usage, you will usually get a life of one year or more from the 18650 battery.

18650 battery characteristics and technical specifications

  1. Nominal voltage: 3.6V
  2. Nominal capacity: 2,850 mAh
  3. Minimum discharge voltage: 3V
  4. Maximum discharge current: 1C
  5. Charging voltage: 4.2V (maximum)
  6. Charging current: 0.5C
  7. Charging time: about 3 hours
  8. Charging method: CC and CV
  9. Battery weight: 48g (about)
  10. Battery size: 18.4 mm diameter and 65 mm height

18650 battery Applications

  • Portable electronics
  • electric car
  • Solar equipment
  • Power wall
  • mobile power
  • Laptop’s battery

How to use 18650 battery

18650 batteries are lithium-ion type chemicals, so you must be careful when using them. This includes charging and discharging the battery at the same time. When discharging the battery, care should be taken not to consume more C rated current, and never to discharge below 3.0V. Generally, if any problems occur, a circuit will be used to monitor the discharge current and undervoltage value to disconnect the battery from the load. Care should also be taken not to subject the battery to short circuits or reverse connections. If you use a single 18650 battery, it is highly recommended to use a battery protection module such as the TP4056 to safely charge and discharge these modules.

Where to use 18650 batteries

18650 battery is a lithium-ion battery, which has been used in many fields, such as portable electronic products such as flashlights, electric cars / cars such as Tesla and so on. The main reason for the success of this battery is its superior performance over competitors. These characteristics include current carrying capacity, voltage, cycle life, storage life, safety and operating temperature, and more. The following table shows a comparison of key parameters between commonly used batteries.

Lead Acid vs Ni-Cd vs Ni-MH vs Alkaline vs Li-ion vs Li-Polymer Batteries

ParameterLead AcidNi-CdNi-MHAlkalineLi-IonLi-Polymer
Cell Voltage2V1.2V1.2V1.5V3.6V3.7V
CostLowModerateHighVery LowVery HighVery High
Internal Resistance (IR)LowVery LowModerateVariesHighLow
Self Discharge (%/month)2% to 4%15% to 30%18% to 20%0.3%6% to 10%5%
Charge Cycle500 to 2000500 to 1000500 to 800Low1000 to 1200>1000
Overcharge ToleranceHighMediumLowMediumVery LowVery Low
Energy Density (Wh/kg)30 to 4545 to 5055 to 658090 to 110130 to 200
Memory Effect NoYesYesYesNoNo
MaintenanceVery HighHighLowLowLowLow
SafetyHighly SafeSafeSafeSafeUn-SafeUn-Safe

How to choose the best lithium-ion battery ?

The best 18650 battery depends on the needs of the equipment used. You should choose 18650, which is slightly higher than the minimum discharge requirement of the device, and then look at the charging capacity. We recommend Panasonic NCR18650B for flashlight and Samsung 25R for high drainage.

about charging 18650 battey, the charging voltage of the 18650 battery is 4.2V, and the recommended charging current is 1A (0.5C). Similarly, a module like the TP4056 will be very convenient to charge the module and provide protection during discharge.

In general, to obtain a higher voltage level, multiple 18650 batteries will be connected in series or in parallel. In this case, care should be taken to keep all batteries at the same voltage level. This process is called battery balancing, and BMS ( Battery management system) to charge and discharge the battery evenly.

The two most common terms you will encounter when using a battery are the mAh rating and the C rating. An 18650 battery rated at 2850mAh means that when we consume 2.850A from the battery, it will last 1 hour; similarly, if we consume 0.285A from the battery, it will last 10 hours, so we can use the Ah rating Calculate how long your battery will continue to use for your application based on the current consumed.

The 18650 battery’s C rating is usually 1C, which means we can consume up to 2.85A from the battery. This is because (Ah rating * C rating) gives us the maximum current that can be drawn from the battery. For example, if our battery has a C rating of 0.5C, then we can only consume a maximum of 1.42A (2.8 / 2) of battery power.


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