As we discussed in an earlier article in this series, tactical flashlights today are smaller, lighter, brighter, and tougher than ever before. The reason is largely due to advances in LED technology and advances in batteries and battery chemistries. This article focuses on the batteries because we, as consumers, can select our own batteries but generally have to use the LEDs provided by the manufacturers of our lights.
If you want detailed specifics on how batteries work, Google will give you plenty of reading material. For the purposes of this article, it is enough to understand that batteries are devices that store electrical energy in the form of chemical energy, releasing it on demand. By using different materials for the anode, cathode and electrolyte (and arranging the chemicals in different ways), you can change the chemical reaction that produces electricity, and therefore the performance and the power of the battery.
The common disposable or one-time use alkaline AA, AAA, C and D cell batteries from brands like Duracell, Energizer, Rayovac and Eveready usually use a zinc anode and manganese dioxide cathode to produce about 1.5 volts of electricity. To produce more power, you have to uses multiple cells. This is why older flashlights like Maglites usually used at least two or three batteries. The more batteries, the more powerful a bulb you could power.
Newer, one-time use batteries, such as the CR123, use lithium for the anode. When paired with different cathodes and electrolytes, lithium batteries can produce anywhere from 3 to 3.95 volts. They tend to be lighter than the same size of alkaline battery, perform better in cold temperatures, have a longer shelf life, and are far less likely to corrode the insides of your electronics. In short, lithium batteries represent a significant step forward in producing better batteries which result in smaller, brighter flashlights.
CR123s were originally used in cameras and other consumer electronics that needed a more compact power source than two or three AAA or AA batteries. Some clever fellows decided to take advantage of the CR123’s higher voltage to make a brighter flashlight. Early flashlights using the CR123 batteries (such as the Streamlight Scorpion) used incandescent bulbs but as LED technology progressed and they grew in brightness and fell in cost, LEDs were quickly adopted as the light source of choice for tactical flashlights.
Today, your basic tactical light usually requires two CR123 batteries. These same batteries are used in in some EoTech holographic sights and in some night vision gear, giving the careful user an opportunity to minimize their logistical issues by carrying just one kind of back-up battery. The technology in most primary (meaning non-rechargeable) CR123s is fairly mature, reliable and widely available. While not as prevalent as the ubiquitous AA battery, CR123s can be purchased at many convenience and discount stores as well as photography and consumer electronics stores. Of course, these guys usually charge an arm and a leg for them. If you make regular use of these powerful little batteries, we would encourage you to check out our low prices on 10-pack and 50-packs. Because we are a bulk seller, we can offer these for half to a third the price you will find in most retail stores.
Rechargeable CR123s, known as RCR123s, are also available, but will not power tactical lights as long as the primary lithium cells because of their lower capacity. For example, an average CR123 has a rating of 1500 milliamp hours, or mAh, while a typical rechargeable CR123 (or RCR123) has only 700 or 900 mAh. (A mAh is a unit used for measuring power over time and the higher the number of milliamp hours a battery can store, the longer it can power a device.) This means a given flashlight will run only half as long when using the rechargeable CR123 batteries. Some manufacturers discourage the use of RCR123s in their powerful tactical lights, which draw more power, simply because their run times are so short.
Thankfully, there is an alternative to the RCR123 that is both rechargeable and powerful: the 18650. This lithium-ion rechargeable battery will fit in many lights that use the CR123 battery, with one 18650 replacing two CR123s. (Check with your light’s manufacturer or manual to be sure an 18650 will fit in its body. For example, in the PowerTac line, the 18650 will fit in the E5, but not in the Cadet II, which is only an eighth of an inch narrower in diameter. In general, if your tactical light comes with a sleeve for the CR123s, it will fit the 18650.)
The downside of an 18650 is that it will cost more than two CR123s (but less than 10 CR123s). Add in a charger and the expense goes up further. In the long run, the 18650 is much more cost effective because it can be recharged approximately 500 times. So do the math: you can spend $36.95 and get two 18650s with a charger and power your light 1,000 times, or you can spend the same amount of money and buy 24 CR123s, which will allow you to replace your batteries 12 times. And if you only want one 18650, you can buy it and the compact XTAR MC1 charger for about the same cost as 10 CR123s. We generally recommend the two-pack so you always have a spare cell ready.
One other downside that bears mentioning: Rechargeable lithium batteries can get hot and may catch on fire if over-charged, misused, or abused. This has been the case with lithium batteries used for some flashlights, but also with lithium batteries used in, laptops, cars and even planes. (We suggest this January 2014 article from The Economist if you want to read more about lithium battery fires.)
Most brands of lithium batteries are now offered with protective circuits, and many “smart” or “intelligent” chargers have circuitry to prevent over charging and overheating. Avoid generic or unlabeled batteries, and be sure to use a charger designed for your battery. Never try to recharge a primary battery. Never cut, crush or attempt to open a lithium battery, and avoid using one that has been damaged. Finally, if you are still a little worried, then put your charger on a non-flammable surface.
Another solution is to buy a flashlight with an integrated charger, such as the PowerTac E7 or their E8 EDC light. Like the PowerTac Hero, these lights can be charged from a USB port and their stored battery power can be used to charge a device such as a cell phone or tablet through its USB port. Voodoo Tactical also sells a tactical flashlight with a built-in charger.