Best 21700 Battery For LED Flashlights

May 11, 2023 | XTAR

The 21700 flashlight has been a recent development in the flashlight industry, and it has quickly gained popularity among flashlight enthusiasts and professionals alike. These flashlights vary in size, output, and features, but they all offer the benefits of using the larger 21700 battery, including longer runtimes and higher output. Therefore it has also led to the development of 21700 batteries. Many battery manufacturers have begun producing 21700 batteries with capacities ranging from 4000mAh to 5000mAh, and with discharge rates of up to 30 amps. Then, what’s the best 21700 battery for LED flashlights?

Here we picked eight 21700 models from different brands based on their reviews. You can see the specification comparison in the following table:

Brand/Model Size Capacity Discharge Rate Voltage Dimentions Protected Positive Terminal Price
Samsung 50E 21700 5000mAh 9.8A 3.6V 20.25mm x 70.8mm No Flat Top $6.90
Epoch 50G 21700 5000mAh 10A 3.7V 21.1mm x 72.9mm No Button Top $12.99
XTAR 21700 5000 21700 5000mAh 10A 3.6V 21.5mm x 74.5mm Yes Button Top $11.90
Acebeam IMR 21700 21700 5100mAh 15A 3.7V 21.3mm x 74.8mm Yes Button Top $22.95
Nitecore NL2150 21700 5000mAh 5A 3.6V 21.4mm x 74.2mm Yes Button Top $24.95
Klarus 21GT-50 21700 5000mAh 15A 3.6V 21.7mm x 75.8mm Yes Button Top $24.95
Molicel M50A 21700 5000mAh 15A 3.6V 21.2mm x 70.0mm No Flat Top $8.99
LG M50LT 21700 5000mAh 14.4A 3.6V 21.10mm x 70.20mm No Flat Top $7.99

There are 4 unproteced 21700 batteries and 4 protected 21700 batteries listed in the table. The unproteced batteries are cheaper in price, and smaller in dimentions. Actually protected 21700 batteries are more difficult to find in the market. We can see from the table that, XTAR 21700 5000mAh is the best choice among the protected 21700 batteries. It has a high capacity and proper discharge rate with a very low price compared with others.

Unproteced or protected 21700 batteries for flashlight?

This is a big topic in flashlight community. I personally would recommend protected cells if they will work for your specific uses. Never a bad idea to have an extra safety feature. But if your flashlight has a built-in overdischarge protection, there should be no problems in using an unprotected cell. Actually there are four factors to consider when decide to buy an unproteced or proteced cell for your flashlight.

Firstly, there are some lights that REQUIRE an unprotected cell to function properly. Take my TK75vn for example, it was current boosted, my standard protected cells would not maintain turbo mode. After just a few seconds, it would step down. So obviously I had a good reason to go unprotected in that case.

Another reason is the size. The protection circuit usually adds at least 2-3 mm to the length of the cell. And in some cases, it adds almost 5 mm. This does lead to issues in the real world. Some lights have tight tolerances, and adding just that little extra length can mean the cell doesn’t fit at all.

Safety is also a very important factor. For single-cell lights (having buck-only or linear regulation, or direct drive) and if you know what you’re doing, unprotected cells are okay. If not, better use protected cells. At least until you have a bit more experience using Li-ions. Protected Li-ion cells are needed for lights that use two or more in series. They are also needed for single-cell lights which incorporate boost circuitry.

It is also a fact that protected cells definitely are more expensive. Maybe not by a lot, but to some people it makes a difference.


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