It can be easily seen that there are many types of rechargeable batteries for the flashlight on the market, which can be divided into 2 groups including Nickel and Lithium batteries. In this article, the author just focuses on the introduction of Lithium because the battery is quite popular in the high-power for the best tactical flashlight. Only battery made from Lithium Cobalt Oxide, also known as Li-ion batteries, can  reach the optimal efficiency of storage capacity.

Nicd (Nickel Cadmium) And Nimn (Nickel Metal Hydride)

The two types of rechargeable batteries are most common in sizes AA, AAA, C, D. The advantage of this material is high safety, good storage capacity. The Voltage for storage is commonly 1.2V. This is not the main problem, for example, many people have wondered why AA 1.2V rechargeable batteries can be used well at their devices while taking good Akaline 1.5V batteries? In fact, when starting, the battery Akaline 1.5V has V load down very quickly in about 1.1-1.2V. And the rechargeable battery falls slowly and in most of the time used well is also in 1.1 – 1.2 V, all types will eventually run out of energy when reaching approximately 0.9V.

However, the disadvantage of Nickel rechargeable battery is the memory effect, if you use a cheap charger or charging improper such as the charging time is too short, or sudden withdrawal the charge, then the lifetime of the battery will be shorter, the battery will be faster broken. Therefore, do not regret the money buying the good Adaptor from reputable firms.  Some rechargeable batteries recommended are Sanyo Eneloop, Panasonic Elvota, GP Recyco +, Sony.

Lithium Battery

Licoo2 (Lithium Cobalt Oxide)

It is used a lot in the rechargeable devices such as mobile phones, laptops, music players. The battery (cell) will be commonly stored in the voltage 3.7V or its coefficient. These cells exist in the ordinary form such as AA, AAA or CR123A. But usually, they are named according to the size of each cell code

  • AAA: 10440 cell, it means that the size of battery is 10mm x 44 mm x 0 (the No. 0 usually indicates cylindrical)
  • AA: 14500 cell
  • CR123A: 16 340 cell
  • 17500, 18500, 17670, 18650: These codes are often found in the computer cell rather than the civil

In addition, it also exists in the larger size, which is equivalent to the C, D Akaline batteries.

The battery has a huge archive of energy density. The Li-ion battery has advantage such as no memory effect, the fast time for charging and discharging time (battery) compared with the Nickel batteries without affecting the battery life. But the disadvantages of Li-ion battery is easy to be explosive compared with Nickel battery if using incorrect due to charging the maximum voltage of 4.2V. Typically, from 4.2 to 4.3V will quickly reduce the battery life and if it reaches 4.4V, the Li-ion will be very dangerous, which can cause an explosion, or during use in high temperatures exceed 60 degrees.

Therefore, to minimize this problem, the manufacturers have added li-ion battery the management circuit for automatically short-circuit protection (short-circuits protected) when the charging process exceeds 4.2V or fall below 3-3.5V (depending on the manufacturer). And, you should use the high-quality rechargeable type as Utrafire, Trustfire, Tenegry, Pila, Wolf-eyes, these chargers are closed-circuit protection when the battery is fully charged 4.2V. For the type of cheap charger, this circuit is not stable.

In addition, the Li-ion rechargeable battery also has a 3V version (actually 3.2V) commonly in cell 16340. Actually, this is 3.7V battery but it has an external circuit with the protected feature. Besides, it has added a function of ability to automatically adjust the voltage down to 3.2V within ten milliseconds.

LiFePO4 (Lithium Iron Phosphate)

Usually, it is only used in cell 16 340, and V = 3V (3.2V in practical), it is clearly stated on the body itself the letter Life Battery. The battery is quite consistent with the flashlight, which requires high V battery or its size. The advantage is that it does not have the fire phenomenon compared with Li-on, so it does need the protection circuitry. As you read on, the Li-ion battery having the protection circuit will increase the size of the battery. For example, for battery CR123A, the standard size is 16×34, then the protected rechargeable batteries generally fluctuate in size 16.5 – 17.2 x 35 – 36.2.

In contrast, its drawback is the poor storage capacity compared with Li-ion, just about 350-400mAh (compared to 600-750mAh in Li-ion and 1000-1400mAh in primary)