All You Need to Know About 18650 Batteries

18650 batteries are lithium-ion rechargeable batteries that are becoming increasingly popular in various high-drain devices. These batteries look like oversized AA batteries but are not as common. If you discover one in a tactical flashlight or an electronic device, this guide will help you find the right replacement battery.

 

What Are 18650 Batteries?

18650 batteries are lithium-ion rechargeable batteries with a nominal voltage of 3.6 or 3.7 volts. The battery’s name comes from its dimensions, which are 18 millimeters in diameter and 65 millimeters in height. You’ll find 18650 batteries in a wide range of high-drain devices such as flashlights, power banks, or even electric cars, thanks to their reliable features, which include high density, long runtime, low self-discharge, and a large number of life cycles.

Because of their popularity, they have many variants that you can choose from. It can cause confusion sometimes, but don’t worry—we’ll break down their differences to help you pick the right one for your device.

 

Capacity (mAh)

The first way to differentiate them is their capacity, often labeled as mAh or milliamp-hour. The higher the capacity means there’s more energy stored inside the battery, and more energy means more runtime on your device. 18650 batteries currently have a capacity ranging from 2000 mAh to 3500 mAh.

For example, some 18650 batteries have:

So if you want your device to last longer, you want to select an 18650 battery with a higher capacity. However, you’ll also need to pay attention to the continuous discharge current of the battery. In some cases, a higher capacity may have a lower discharge current than a lower capacity battery, and if your device requires a high current input, you’ll have no choice but to select the lower capacity ones.

 

Maximum Continuous Discharge Current

That brings us to the next difference among 18650 batteries, which is the maximum continuous discharge current. It’s important to buy batteries that provide the same amount or more current than your device needs. Using a lower current rating battery will cause it to overheat because the battery has to work harder than it can handle.

For example, if your device requires 5A continuous input, your options would be batteries that can handle at least 5A of continuous discharge current.

 

Flat Top vs. Button Top

18650 batteries have two slightly different types and sizes:

The positive contact of the flat top battery is flat, while the positive contact of the button top protrudes a little. Because of this, the button top battery is slightly higher than the flat top battery. A majority of 18650-powered devices should be compatible with these two types of batteries, especially those that have a compression spring in their battery compartment.

However, when in doubt, you can either look at the previous battery in your device or check the battery’s dimensions before purchasing to confirm if it’ll fit.

 

Protected vs. Unprotected Batteries

Another difference among 18650 batteries is whether they include a protection circuit board (PCB). So when buying batteries, you’ll have two choices between batteries that have a PCB built-in and a bare cell battery, which does not have a PCB.

A battery with a PCB has a small electronic circuit board built into the battery, which monitors the parameters of the battery to prevent some potential problems such as over-draining, short-circuiting, or overheating. A bare cell battery doesn’t have a built-in PCB, so they risk running into over-discharging, overcharging, and overheating issues.

You’ll have to pay extra attention and care when choosing these batteries because lithium-ion 18650s are very powerful cells and can cause real damage if not used properly. But without a PCB, they are slightly shorter in size and cheaper compared to batteries with a PCB.

We recommend choosing a battery with a PCB over a bare cell battery, especially if you’re new to 18650 batteries and are using them in devices like tactical flashlights. They may cost more, but the peace of mind is worth the price.

 

Charging Options

Moving on to the next difference, there are two charging options to recharge 18650 batteries:

If you have just a few 18650 batteries and don’t use them often, it may be a better idea to buy batteries that have built-in micro USB ports to recharge. This way, you don’t need to buy an extra charger—just connect it to a micro USB to USB cable and let it recharge.

For those who use a lot of 18650 batteries, though, it’ll be more convenient to buy batteries and the chargers separately and then charge them all at the same time. For some chargers, you can also select different charge currents and check the battery’s capacity, which is not possible with batteries that have a built-in micro USB port.

We hope this guide can help you learn more about 18650 batteries and find out which one is right for your project. If you have any questions or suggestions, please leave them in the comment section.

 

FAQs of 18650 Battery

Q1: What devices commonly use 18650 lithium-ion batteries?

A1: 18650 lithium-ion batteries are commonly used in high-drain devices such as flashlights, power banks, laptops, and even electric vehicles. Their high energy density and long life cycles make them ideal for devices that require reliable and long-lasting power sources.

 

Q2: Is it safe to use unprotected 18650 batteries?

A2: Using unprotected 18650 batteries (without a built-in PCB) can be risky if not handled properly. They lack the safety features that prevent overcharging, over-discharging, and short-circuiting. It’s recommended for beginners or general users to opt for protected batteries to ensure safety and device compatibility.

 

Q3: Can I charge 18650 batteries with a regular battery charger?

A3: No, 18650 lithium-ion batteries require a charger specifically designed for lithium-ion cells. Using an incompatible charger can lead to battery damage or safety hazards. If you have batteries with a built-in micro USB port, you can charge them using a standard USB cable.