18650 vs AA Battery: What’s the Difference?

18650 vs AA batteries, they are both cylindrical batteries, and these two batteries are very commonly used, so it will cause a general problem, whether these two batteries can be used interchangeably. But in fact, these two kinds of batteries have relatively big differences, such as size, capacity, voltage, charge and discharge characteristics, and battery chemistry.

What is 18650 batteries?

It is a standard lithium-ion battery model set by Japan’s SONY company in order to save costs. The 18 means a diameter of 18mm, 65 means a length of 65mm, and 0 means a cylindrical battery, Larger than AA batteries.

The 18650 battery has a nominal voltage of 3.7V, it is rechargeable with higher capacity and store more energy, longer life than AA battery. the capacity can reach 1800 to 3500mAh, and the anode of the 18650 battery has a flat shape and a tip shape.

There is a clear difference between the 18650 vs AA battery we usually use. 18650 batteries are not unchangeable batteries, but batteries with a diameter of 18mm, which are generally Lithium ion batteries.

The biggest advantage of the 18650 is the high energy density chemistry of the lithium-ion battery, which supports charging and can form a battery pack with higher voltage, but requires the protection of BMS to avoid overcharge and overdischarge.

Read More:

What is AA battery?

The AA battery is 14mm in diameter and 50mm in length. The size is smaller than the 18650 battery, and the AA battery is the same size as the 14500 battery. The nominal voltage is 1.5v and the capacity ranges from 1800mAh to 2800mAh.

AA batteries commonly used in the market are not rechargeable. AA battery rechargeable and non-rechargeable battery chemistry becomes different:

  • Rechargeable AA battery Chemical composition: nickel-cadmium battery, nickel-metal Hydride battery, nickel-zinc battery, ultra-low self-discharge nickel-metal Hydride battery, lithium iron phosphate rechargeable battery, 3.7V to 1.5V lithium polymer battery
  • Non-rechargeable AA battery Chemical composition: hydrogen-oxygen fuel cell, alkaline battery, carbon battery, disposable lithium battery

What is the difference between 18650 vs AA batteries?

Different sizes

Although 18650 and AA batteries look alike, the size of the two is actually different. The specification of 18650 lithium battery is 18 mm in diameter and 65 mm in length; while the specification of AA battery (in fact, the scientific name of AA battery is 14500 battery) is 14mm in diameter and 50mm long. 18650 is much larger in length and diameter than AA batteries.

Different voltage

The voltage of 18650 lithium ion batteries is generally around 3.2 to 3.7V, the most common one is 3.7V; while the voltage of AA batteries is 1.5V.

Capacity

18650 battery capacity is generally 1800mAh to 2800mAh, AA battery capacity is generally 2200mAh to 5500mAh.

18650 battery capacity can be reused by charging, with no memory effect, and no need for full charge storage.

Chemical reaction

Its working principle (internal chemical reaction process) is different:

  • 18650 Rechargeable lithium-ion battery, lithium iron phosphate or NiCoMn ternary material.
  • AA can be alkaline batteries, zinc-carbon batteries, nickel-cadmium batteries, nickel-metal hydride batteries (NiMH), and lithium-ion batteries.

18650 is a rechargeable battery, and most of ordinary AA batteries are disposable batteries, which are rarely rechargeable or cannot be recharged.

Performance

The 18650 has a higher energy density and is larger, allowing it to store more energy. AA batteries have a lower capacity and are usually used for single use.

Lifespan

The 18650 battery generally has a cycle life of 3000 times 80%DoD. AA alkaline batteries are usually disposable and non-rechargeable.

18650 vs AA batteries, What are the advantages of 18650 lithium batteries?

  1. Large capacity, The capacity of the 18650 lithium battery is generally between 1200mah and 3600mah, while the general battery capacity is only about 800mah. If combined into a 18650 lithium battery pack, the 18650 lithium battery pack can easily exceed 5000mah. Read more about capacity: Wh vs Ah
  2. Longer Service Life
  3. Higher safety performance. 18650 lithium battery has high safety performance, no explosion, no combustion; non-toxic, non-polluting, RoHS trademark certification; all kinds of safety performance in one go, the number of cycles is more than 500 times; high temperature resistance performance,  The discharge efficiency reaches 100% under 65℃. In order to prevent the short circuit of the battery, the positive and negative electrodes of the 18650 lithium battery are separated. Therefore, the possibility of short circuit phenomenon has been reduced to the extreme. A protection board can be installed to avoid overcharging and over discharging of the battery, which can also prolong the service life of the battery.
  4. High voltage. The voltage of 18650 lithium batteries is generally 3.6V, 3.8V and 4.2V, which is much higher than the 1.2V voltage of nickel-cadmium and nickel-metal hydride batteries. (click here to learn about NPP High Voltage Battery)
  5. No memory effect. It is no need to empty the remaining power before charging, which is convenient to use.
  6. Little internal resistance
  7. It can be connected in series or in parallel to form a 18650 lithium battery pack
  8. Wide range of use.

Can the 18650 battery replace the AA battery?

You can’t. By comparison, the 18650 battery is indeed better in performance, but the voltage, size, and significantly different.

The application of these two batteries is also different, and the forced use of 18650 batteries to replace AA batteries will cause damage to the device

18650 vs AA battery: Which one is better?

From a commercial point of view, these two batteries have a broad market in their respective fields, AA battery and 18650 battery have their own application fields.

In small equipment such as toys, and remote control, AA battery is very suitable for this battery performance requirements are not high equipment field. In the field of new energy storage and electric vehicles, the high performance of 18650 highlights its advantages, and the emergence of lithium-ion batteries has led to more and more high-tech industries.

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