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Lumens Factory E Series LED Head Unit & Bulb 3 - 3.7 Volts - 3 Mode
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Home > Rechargeable Lithium Battery Information - Protected vs. Unprotected Li-Ion Batteries - Lithium Ion Battery
 

Rechargeable Lithium Battery Information - Protected vs. Unprotected Li-Ion Batteries - Lithium Ion Battery

Rechargeable Lithium Batteries (Li-Ion or Li-on Batteries) represent a great leap forward for many lithium-powered flashlight owners, but they come with risks as well as rewards.

The primary difference between the Protected and Unprotected batteries is that the protected batteries have a small circuit board, typically on the bottom of the battery, that stops the charging or discharge of the battery in certain circumstances. Some of the circumstances in which the circuit include: Over-Charge, Over-Discharge, Short-Circuit, and in some cases, overheating.

CR123a batteries, which power most Lithium-powered flashlights produce 3 volts of power per battery for most of their useful life. The standard flashlight configurations use 1, 2 or 3 of these batteries, only exceptional flashlights like the SureFire® M4 and SureFire® M6 use more than 3 batteries. CR123a batteries have been in production for more than 20 years, and they are very safe and reliable. Unless the metal body of the battery is ruptured, or the battery is burned in a fire, these batteries are very unlikely to have any problems. These batteries should NEVER be recharged, they will probably explode if you try to recharge them.

Due to the high cost of powering flashlights with CR123a batteries, the battery industry has developed a new class of batteries known variously as R123, R123a, RCR123, RCR123a, 16340, etc. batteries. Though these batteries are about the same size as the common CR123a batteries, most of the rechargeable batteries produce 4.2 volts of output when fully charged, so they will instantly overpower and destroy flashlights and other devices that are designed for CR123a batteries.

Li-Ion Batteries, or Lithium Ion Batteries, have the advantages of having a very low self-discharge rate, virtually no memory effect, and can be recharged hundreds of times during the life of the battery. Self-discharge refers to gradual declining power available from rechargeable batteries while they sit on the shelf. Memory Effect refers to the tendency of rechargeable batteries to have a lower total level of power available as they get older. Neither of these are serious problems with Li-Ion batteries.

The most common Li-Ion batteries on the market are the RCR123 PROTECTED 3.6 volt lithium batteries. These batteries have a very small circuit inside of them that shuts them off in the event that they are over-charged, over-discharged, overheated or short-circuited. These batteries are the best choice for most applications. These batteries require special chargers that are specifically designed to charge lithium rechargeable batteries.

The second most common Li-Ion batteries on the market are the 18650 PROTECTED 3.6 volt lithium batteries. These batteries are the length of two CR123's and a high mAh for extended runtimes. They also have a very small circuit inside of them that shuts them off in the event that they are over-charged, over-discharged, overheated or short-circuited. These batteries are the best choice for most applications. These batteries require special chargers that are specifically designed to charge lithium rechargeable batteries.

Other Li-Ion batteries available today include the CR-123 size 3.6 volt UNPROTECTED lithium batteries. They produce 4.2 volts of power when fully charged, then quickly fall to 3.6 volts output. They output 3.6 volts until they are mostly discharged, at which point the voltage falls rapidly. If they are discharged below 3 volts, they will be ruined and no longer usable. The user must be very careful not to let this occur. These batteries should only be charged in a charger specifically designed for them, as those chargers have a circuit that stops charging the battery when they reach 4.2 volts. All of the Li-Ion chargers that we sell are designed to charge both Protected and Unprotected batteries.

The best flashlights for rechargeable batteries are LED flashlights that are specifically designed for use with rechargeable batteries. These flashlights have protective circuitry that shuts down the flashlight when the voltage crosses below 3 volts, preventing damage to the batteries. Many LED flashlights and LED flashlight heads are capable of handling the higher voltage of rechargeable batteries, including the NovaTac EDC series flashlights, the Fenix line of flashlights, and the Lighthound Cree drop-in adapters for SureFire® and other flashlights.

The most common incandescent SureFire® flashlight is the SureFire® 6P or G2. These lights both use the P60 bulb, which is a 6 volt incandescent bulb. This bulb CANNOT HANDLE the voltage of rechargeable batteries. Fortunately there is another option, the Lighthound Cree drop-in, which can handle 9 volts of power and works very well with the 7.2-8.4 volts of power supplied by two rechargeable lithium batteries. Another option is the Lumens Factory line of incandescent bulbs, which are specifically designed for rechargeable batteries and fit most of the popular SureFire® flashlights.

Please email us before using any rechargeable batteries if you have any questions or concerns. It is the responsibility of the buyer to be aware of the requirements and limitations of rechargeable batteries before using them. Note that many flashlight manufacturers will void your warranty if you tell them that you have used rechargeable Li-Ion batteries in their flashlights.

Link to third party SureFire rechargeable compatibility information: http://talisiorder.ca/sfxre.html


The other types of rechargeable lithium batteries used in flashlights are the 18650 and 17670 3.6 volt rechargeable lithium batteries. Both of these types of batteries output 3.6 volts, but they have much longer run time than the RCR123-size batteries. The 17670 batteries are the same diameter as the RCR123 batteries, but they are twice as long. The 18650 batteries are larger in diameter than the RCR123 batteries, and they are the same length as the 17670 batteries.

18650 and 17670 batteries are available in both protected and non-protected versions, Pila (Wolf-Eyes) has been selling the protected version of these batteries for some time, they refer to them as the Pila 168A (18650) and the Pila 168S (17670).

Use of the 18650 and 17670 batteries is primarily limited to flashlights that are specifically designed for them.

Please email us before using any rechargeable batteries if you have any questions or concerns. It is the responsibility of the buyer to be aware of the requirements and limitations of rechargeable batteries before using them.

Size Chart
This is a chart that illustrates the approximate sizes of the various rechargeable lithium batteries that we sell. The numerical designation of the battery gives an approximation of the size. For example, a 10280 battery is approximately 10mm in diameter and 28mm tall, the final 0 indicates that it is round. Please note that the sizes are approximate, and some batteries, especially protected batteries, may be too large to fit your particular application, please check the exact sizes before ordering.


10180 battery - 10mm x 18mm (1/3 AAA size)
10280 battery - 10mm x 28mm (1/2 AAA size)
10440 battery - 10mm x 44mm (AAA size)
14250 battery - 14mm x 25mm (1/2 AA size)
14500 battery - 14mm x 50mm (AA size)
16340 battery - 16mm x 34mm (nominal CR123a size)
17335 battery - 17mm x 35mm (nominal CR123a size)
17500 battery - 17mm x 50mm - slightly wider than CR-123, fits most lights, but 1.5 times the height of the typical CR-123a battery - two of these will generally replace three of the CR-123a batteries

17670 battery - 17mm x 67mm - about the size of two CR-123a batteries, but less overall voltage, 4.2v max vs. 6v max from two primary batteries

18500 battery - 18mm x 50mm - wider than CR-123a, about 1.5 times the height of a single CR-123a battery, these will only fit lights designed for their wider size

18650 battery - 18mm x 65mm - wider than CR-123a, about 2x the height of a single CR-123a battery, these will only fit lights designed for them


Lighthound, INC. - Lithium Batteries, Li-Ion Batteries, Fenix Flashlights, Cree LED flashlights, spyderco Knives, Leatherman Multitools, and MORE!

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