Overview of 3.7 V 18650 Battery

By Gerald, Updated on April 25, 2024

Part 1. What is the 3.7 V 18650 battery?

The 3.7V 18650 battery is a rechargeable lithium-ion cell with a standard nominal voltage of 3.7 volts. Its name derives from its dimensions: 18mm in diameter and 65mm in length. Widely utilized in various electronic devices such as laptops, flashlights, and power tools, this battery offers a balance of compact size and high energy density.

The 3.7V rating signifies its average voltage output during discharge, ensuring consistent power delivery. With capacities ranging from around 1500mAh to over 3000mAh, these batteries cater to diverse energy requirements.

Part 2. 18650 battery voltage

18650 battery voltage is one of the important parameters of an 18650 lithium battery. Normally, the voltage of a single 18650 cell is as follows:

1. Working voltage

The core of the 18650 battery voltage is the working voltage, also called the nominal voltage, which is 3.7V. This is equivalent to three nickel-cadmium or nickel-metal hydride batteries connected in series. Some battery manufacturers design the working voltage of 18650 batteries to be 3.6V.

2. Charging limit voltage

This is the maximum limit for the 18650 battery voltage, which is 4.2V. The 18650 battery charging process increases the 18650 battery voltage from 3.7V during operation to 4.2V. The process ends, indicating that the battery is fully charged. If it exceeds 4.2V, it is overcharged, which will cause damage to the 18650 battery.

3. Discharge termination voltage

That is the voltage of the 18650 battery drops to the lowest working voltage, which is unsuitable for continuous discharging, which is 2.75V. If the battery is placed below the cut-off voltage, it is over-discharged. Over-discharging the battery will damage the electrode structure of the 18650 battery, causing irreversible reactions of lithium ions, seriously affecting the life of the 18650 battery.

Overcharging and over-discharging will cause serious damage to the 18650 battery. Therefore, most 18650 batteries have PCBs that allow the 18650 battery voltage to automatically stop when it reaches the upper and lower limits.

Part 3. Voltage and capacity of 3.7 V 18650 battery pack

3.7v 18650 batteries can be connected in series, parallel, or series-parallel to form an 18650 battery pack.

1. 3.7 V 18650 battery pack after parallel connection

The capacity of the 18650 battery pack is the sum of the capacities of multiple cells. The voltage of the 18650 battery pack is the same as that of a single 18650 cell.

Take two 2200mAh 3.7 V 18650 batteries connected in parallel to form an 18650 battery pack as an example. The voltage of this 18650 battery pack is still 3.7V. But the capacity of 18650 battery pack is 4400MmAh;

2. 3.7 V 18650 battery pack connected in series

The capacity of the 18650 battery pack remains unchanged. The voltage of the 18650 battery pack is the sum of the voltages of multiple 18650 cells.

Take three 2200mAh 13.7 V 18650 batteries connected in series to form an 18650 battery pack as an example. The voltage of the 18650 battery pack is 11.1V. However, the capacity of the 18650 battery pack is still 2200mAh.

3. Series and parallel 3.7 V 18650 battery pack

Multiple 3.7 V 18650 batteries are connected in series and parallel to form an 18650 battery pack. At this time, the voltage capacity of the 18650 battery pack is the sum of the voltage and capacity of multiple 3.7 V 18650 batteries. For example, take the 18650 battery pack composed of three series and two parallel 2200mAh 3.7 V 18650 batteries. The voltage of the 18650 battery pack is 11.1V, and the capacity of the 18650 battery pack is 4400mAh.

The above 11.1V is the working voltage of the 18650 battery pack after the series and series and parallel connections. The charging limit voltage and discharge termination voltage of the 18650 battery pack also change with the series connection of the 3.7 V 18650 battery. For example, the charging limit voltage of a battery pack composed of three 3.7 V 18650 batteries in series and three series and two parallel 3.7 V 18650 batteries is 12.6V. The discharge end voltage of the battery pack is 8.25V. The relevant values for parallel battery packs are still 4.2V and 2.75V.

The combination of 3.7 V 18650 batteries causes different changes in the voltage of the 18650 battery pack. The 8650 battery pack has a voltage and capacity obtained by combining the voltages and capacities of multiple 3.7 V 18650 batteries. This allows 18650 batteries to be used in more areas.

Part 4. What is the difference between the 3.6 V and 3.7 V 18650 battery?

Here’s a concise list outlining the similarities and differences between 3.6V and 3.7V 18650 batteries:

3.6V and 3.7V 18650 batteries Similarities:

Both are variants of the 18650 lithium-ion cell.
They share similar physical dimensions and cylindrical shape.
Both are rechargeable batteries commonly used in various electronic devices.
They typically feature similar chemistry, consisting of lithium-ion technology.

3.6V and 3.7V 18650 batteries Differences:

1. Nominal Voltage:

3.6V 18650 battery: Nominal voltage of 3.6 volts.
3.7V 18650 battery: Nominal voltage of 3.7 volts.

2. Performance:

The 3.7V variant may offer slightly higher energy density and capacity than the 3.6V version.
The 3.7V battery might increase power output and potentially longer runtime in certain applications.

3. Compatibility:

Both batteries are generally compatible with various devices and applications.
The 3.7V variant might be preferred for devices that require higher voltage thresholds or demand more power.

4. Voltage Fluctuation:

The actual voltage output of both batteries can vary based on factors such as charge level, temperature, and load conditions.
Despite nominal voltage differences, both batteries exhibit similar fluctuations during operation.

5. Usage:

Depending on specific application requirements, one variant may be chosen over the other to optimize performance and efficiency.
Both variants are reliable power sources for portable electronics, power tools, and other devices.

While 3.6V and 3.7V 18650 batteries share many similarities in physical attributes and applications, their nominal voltage ratings and potential performance differences distinguish them from each other, making each variant suitable for particular use cases.

Part 5. 2600mah 3.7 v rechargeable 18650 battery

The 2600mAh 3.7V rechargeable 18650 battery provides a favorable balance of capacity, size, and cost for many general applications. It offers 9.6Wh of energy storage and maintains portable dimensions within a standardized 18650 casing while delivering over a full day’s power for most portable gadgets.

Popular brands like Samsung, LG, and Ufine reliably produce 2600mah 3.7 v rechargeable 18650 batteries, maintaining 80% or greater capacity after 500 charge cycles. D

Devices utilizing these mid-range capacity batteries include vaporizers, flashlights, power banks, and lower-drain power tools. The additional energy afforded versus slimmer alternatives extends runtimes noticeably without compromising form factors.

Part 6. 18650 battery 3.7v 2200mah

Some ultra-compact devices favor the marginally smaller 2200mAh 3.7V 18650 battery. Slightly shorter than standard 2600mAh equivalents, they maintain an energy supply of 8.1Wh within a more space-saving cylindrical package.

This makes the 2200mAh cell well-suited for applications where minimizing dimensions matters most, such as true wireless earbuds or other wearable electronics.