All about 18650 rechargeable batteries that you want to know

What does a 18650 rechargeable battery mean

What is a 18650 rechargeable battery means? 18650 is named after the dimensions of the battery. Let’s understand the fact by operating the digit 18650.

In short:

● 18mm (Diameter)

● 65mm (Height)

● 0 (Cylindrical shape)

Is a 18650 battery Lithium? Yes, it’s a Lithium-ion battery by its chemistry.Although the number 18650 only indicates the size of the battery, it does not specify the battery material. However, 18650 rechargeable batteries existed in the form of lithium-ion batteries from the beginning of their birth, and became one of the most popular cylindrical batteries on the market after commercialization. Therefore, all 18650 batteries are lithium-ion batteries.

How do 18650 rechargeable batteries work

The working principle of all lithium ion batteries is the same. Here is an article explaining How do lithium ion batteries work in detail.The positive electrode of the 18650 cells contains lithium atoms. The negative electrode contains graphite.

● Charge and discharge: During charging, lithium atoms are released from the metal oxide. It will generate a lithium-ion. The electrolyte will allow lithium ions only to pass through. Lithium ions will go to the negative electrode and stay there.

● During Discharge: The shifting of ions will be started to go back to the metal oxide.

What are the common sizes of cylindrical Li-ion batteries

Cylindrical lithium-ion batteries are represented by 5-digit numbers which show their size dimensions. These are found in many sizes.

14500 Li-ion batteries

○ Its capacity is from 700 -1000 mAh

○ Its size is 14mm (diameter), 50mm (height)

18650 batteries

○ Its size is 18mm (diameter) ,65mm ( height)

○ Its capacity is generally between 1200~3600mAh

○ Its nominal voltage is 3.2/3.6/3.7

21700 batteries

○ One of the most common usage scenarios is these batteries are replacements for 18650 in Energy storage/EV battery packs

○ Its size is 21mm (Diameter) , 70mm (height)

○ Its nominal voltage is 3.2/3.6/3.7V

○ Its capacity is from 4000-5000 mAh

26650 batteries

○ Its size is 26mm (diameter), 65mm (height)

○ Its capacity is high at 5200mAh

32700 batteries

○ Its size is 32mm (diameter), 70mm (height).

○ Its capacity is 5000-6500mAh.

Are all 18650 rechargeable batteries the same

All 18650 batteries are not the same as they have certain different factors by which they can be distinguished:

❶ 18650 Chemistry: These batteries can differ by chemistry although all are lithium-ion batteries. The most common types are ternary lithium and lithium iron phosphate.

❷ 18650 Dimensions: 18650 lithium batteries have slightly different dimensions by different manufacturers. A 18650 battery is 18mm wide and 65mm high.

❸ 18650 specification parameter: The 18650 produced by different manufacturers also has some differences in various specifications, such as capacity, nominal voltage, charge and discharge current, number of cycles, and so on.

We can check either its 18650 or not by two things:

❶ By physical appearance: This can be done by the general look of the appearance of the battery by its color, shape, size and specs printed on the battery.
❷ By voltage measuring test: As 18650 batteries reach up to 4.2 voltage. So we can check the battery by performing a voltage test.

How much power does a 18650 rechargeable battery have

Power of 18650 rechargeable battery: Power = voltage x current

If a standard 18650 is 3.7v and 3600mAh then the power (Wh) is:3.6Ah x 3.7V=13.32 Wh

How long does a rechargeable 18650 battery last? The life of any battery depends on certain factors; age, capacity, charge cycle and application to which it is applied. If the battery is running beyond its limits, its chemistry will be destroyed and its life will not go long. However, the modern 18650 batteries have 2000-4000 charge cycle but it depends on how you use them eventually.

How many times can you recharge a 18650 battery

The number of times a battery is charged and discharged is called the number of cycles. Many 18650 batteries can reach 4000+ cycles comfortably in the right conditions with the chemistry of LiFePo4.

Generally, We can charge 2000 cycles in life of 18650 batteries. Study shows that the life of a battery is not related to the number of charges but the total charge throughout its life. Shallow charge and discharge are good for battery life. Over charge and discharge destroy the battery. The correct charging method can prolong the battery life.

What is so special about 18650 batteries

The main reason is that 18650 is the longest development time, a lithium-ion cylindrical cell. Compared with other packaging methods, cylindrical cells are the most popular, and 18650 is the most classic specification of cylindrical cells. Due to its wide application and high utilization rate, the standardization of 18650 battery production is also high.

What are the uses of 18650 rechargeable batteries

These batteries can be used in every device from electric cars to energy storage devices due to their versatility. These rechargeable 18650 batteries are used in homes, offices, and industrial departments. A power pack of a hoard of cells can run many devices like Powerwall、portable power station etc.. 18650 lithium-ion batteries are being used in the latest technology because of their reliability and ability to be recharged thousands of times.

Devices run by 18650 rechargeable batteries: These batteries are used in golf cart,  marine, RV, camper etc..

How can you tell a fake 18650 battery

A fake 18650 battery can cause severe injuries and fire so it is important to spot the real one by some identifying codes and signs.

Ⅰ Battery wrapper, color, and code

Wrapper: Check the packaging for damage. Li-ion batteries should be sealed.

Color and Code: The code written on the battery is quite different in font size, text style, and position of the letters.

Ⅱ Manufacture Date and Serial Number

We can also use codes to spot a counterfeit battery.

Ⅲ Top-cap Identification

Take careful notice of any damage or scratch on the top cap to identify the fake battery.

Ⅳ Size and Weight

Check that the dimensions and weight are the same as the numbers in the spec sheet.

Ⅴ Signs of Wear and Tear

Reputable battery manufacturers can never sell batteries with any sign of wear and tear. So notice some of them avoid fake batteries. Some of them can be:

○ Burn Mark
○ Bottom Scratches
○ Rust Spots

What battery can I use instead of 18650

A 21700 rechargeable li-ion battery is a pretty replacement for 18650 batteries. Both are almost similar in their shape, with little difference in width and height.21700 batteries have a similar voltage of 3.2/3.6/3.7V to that of a 18650 but the capacity of 21700 is high from 4000-5000 mAh.

If the materials of 18650 and 21700 batteries are the same, the nominal voltage will be the same. If it matches the voltage and power of the device, you can use 21700 batteries instead of 18650 rechargeable batteries.

FAQs – about charging 18650 rechargeable batteries

Can you overcharge 18650 batteries

Overcharging any type of battery is dangerous. When a battery is fully charged it should be disconnected immediately from the power source. If you leave the battery connected to the power source and exceeds the charging time, overcharging will occur and the battery will swell and be damaged eventually.

How long do new 18650 batteries take to charge

The amount of time to recharge 18650 rechargeable batteries depend on charging current and charging rate.

The higher the capacity of the battery, the longer the time it will take to recharge. If the battery is 2300mAh it may take about 4 hours to charge and if it is 3600mAh it may take 5-6 hours to charge.

What is the voltage of a fully charged 18650 battery

When you charge lifepo4 18650 rechargeable batteries to their fill it reaches 3.65V. This is a safe range. But the nominal standard charge of 18650 batteries is 3.2V.

Can you charge 18650 batteries with USB

Yes, you can charge 18650 batteries with a USB. For this purpose, there are special USB chargers on the market. The good thing about this charger is that you can take it anywhere. and you can use it with any type of USB power port/socket. But it is recommended to use lithium ion battery charger if you want to avoid any hazardous situation. Lithium-ion batteries have high requirements on chargers and need protection circuits, so lithium-ion battery chargers usually have high control precision and can charge lithium-ion batteries with constant current and constant voltage.