The Ultimate Guide to Flashlight Battery Sizes

Written by Theo Lee

Theo Lee is a Contributor for Urban EDC covering our Flashlight column. Opinions expressed by Urban EDC Contributors are their own. Theo enjoys exploring the great outdoors, playing with his German Shepherd, and browsing for his next EDC purchase in his free time. You can follow Theo here.

Every year manufacturers release a plethora of flashlights that are brighter and more efficient than the last year’s. And in a market saturated with options, the difficulty of finding that ‘perfect’ flashlight likewise becomes all the more difficult. That’s where I come in. In this article, I’ll be covering some of the most common battery types and what you should expect from said format. Because there exists many different sizes of batteries, naturally there are trade-offs between each size.

One of the easiest ways to get a general idea of what size battery you’re looking at is by noting the battery’s name. The size of AA/AAA/C/D batteries are common knowledge, but take for example the not-so-common 10280 battery. Even if we’ve never seen or heard of the battery before, those numbers tell us the battery’s dimensions: 10mm x 28mm. The “0” at the end denotes a cylindrical diameter. Now that I’ve explained battery nomenclature, let’s go over some of the most popular battery formats in EDC flashlights.

10180

This is a battery format that has become increasingly popular in recent years. The 10180 is an extremely small, rechargeable battery. They are primarily used in neck-lights and keychain lights because of their diminutive size. 10180 batteries are of li-ion chemistry so even minuscule flashlights such as the Mecarmy Illuminex can put out a lot of light! The 10180 format is great if you don’t need to use a flashlight often or just want a backup to your main flashlight.

10180 flashlights are as photogenic as they are tiny! Pictured are the Veleno Designs Quantum DD38 and Gyorgey Kemene’s Omicron. Both were limited, custom production runs but there’s a huge market for 10180 flashlights.

The obvious drawback of the battery’s small size is capacity. Most 10180 batteries have no more than between 70-100 mAh of capacity. Be vigilant of inflated capacities, and purchase from reliable sources! One other drawback is that it can be hard to find a charger for the battery. Even if you have a flexible magnetic-type charger or use a metal spacer, you can easily damage the 10180 because the current is too high. Almost every mainstream manufacturer that has their own iteration of the 10180 flashlight has an integrated USB port on the flashlight for charging, but it’s still worth noting.

Charging 10180 batteries stand-alone requires a special charger. But most current-generation 10180 flashlights have built in USB charging.

AAA

First off, if you haven’t already, go do yourself a favor and buy some rechargeable, Eneloop batteries. It’s 2018 and there’s zero excuse for still using alkaline batteries. The advantages of rechargeable Ni-Mh over disposable alkaline are numerous, if the savings alone aren’t enough to convince you.

The biggest advantage of the AAA-format is the form factor. AAA flashlights tend to be slimmer and more svelte than their other-battery counterparts. If you need something that’s exceedingly discreet and has decent juice, the AAA-format might just be for you. The AAA battery is also widely available. In the event that your flashlight runs out of battery while you’re in the field, you’ll easily be able to acquire a replacement battery. Battery carriers are also a great storage solution.

So where does the AAA fall short? Well, most AAA flashlights simply don’t have very much output and max out at around 150 lumens. To date, I believe the Surefire Titan Plus is the brightest AAA flashlight on the market, and it’ll only do 300 lumens for a short time before stepping down. Granted, there are some flashlights that do use the 10440 battery. Think of the 10440 battery as a supercharged version of the AAA that uses Li-ion chemistry for insane brightness. But the capacity of 10440s is still very small, and the battery itself is relatively uncommon.

AA

Once again, please, please go rechargeable! AA batteries are pretty similar to the AAA battery in that they don’t allow for much output, but they do have a lot more capacity. I don’t see a lot of AA flashlights on the mainstream market nowadays, but they have their place. As with AAA batteries, they’re quite readily available and are probably the most common battery-type worldwide. There is also a rechargeable, li-ion version of the AA battery called the 14500, but I don’t want to get too much into the different battery chemistries.

CR123a

This is one of the most popular battery sizes for EDC. The CR123a was first pioneered for its reliability, shelf-life, and power. Originally used in most flashlights as pairs, the market has expanded with many flashlights that use just a single CR123a. Generally speaking, the CR123a has an excellent balance of power and size. Many single CR123a flashlights are easily pocketable and provide ample illumination power. Here's a pro tip: Thyrm Cell Vaults are a tough, waterproof storage option specifically designed for CR123a batteries.

Perhaps one of the greatest drawbacks of the CR123a format, though, is that the battery is still predominantly disposable. Most flashlights that use a single CR123a will also allow you to use a rechargeable, li-ion/IMR 16340 battery. With that said, 16340 batteries still lack sufficient capacity, and lithium CR123a are more reliable.

As a comparison, pictured here from right-to-left are two IMR16340, a standard li-ion 16340, and a standard CR123a battery.

18350

This size flashlight battery is one of the most popular in the custom flashlight world. Pretty much every recent “custom” flashlight uses this battery, and for good reason. The latest generation of 18350 have relatively good capacity and allow flashlights to draw high amps for insane output. With only a slightly larger diameter and longer length than the venerable CR123a, there are a myriad benefits to the 18350. This is the format that I use most for EDC. Some may find it a little too robust relative to the CR123a, but the trade-off of greater output, capacity, and rechargeability is worth it to me. The Oveready BOSS 35 is a well-known, custom flashlight that uses the 18350 battery.

Maybe one of the biggest issues with this battery format is actually finding good 18350 batteries. The 18350 battery market is flooded with inflated capacity ratings, and often times inflated draw ratings: 1200 mAh is about the largest capacity you can currently expect from an 18350. Purchasing from a reliable source is critical.

Here is a battery size comparison. From right-to-left are a standard CR123a, IMR16340, and IMR18350. As you can see, the 18350 battery is slightly larger.

18650

The 18650 is the big brother to the 18350. There’s also a middle ground of sorts - the 18500 battery - but that format is largely dead. 18650s have excellent capacity and can provide a lot of power so they’re very popular with most manufacturers. I’d generally recommend the 18650-format if you want both lots of power and lots of capacity.

The disadvantage of this battery is its size. At almost twice the length of an 18350, and basically the equivalent of a 2-cell CR123a flashlight, the 18650 format is not for everyone. Granted, there are some very compact 18650 flashlights on the market. But personally, I’ve found that the 18650-size simply does not work for my EDC. If I need a dedicated flashlight for a certain job or camping, though, this is the format that I lean toward.

Some manufacturers also have begun offering both an 18350 body and a longer 18650 body with their flashlights. Cross-compatibility between the two body sizes allows users to reap the benefits of both worlds, and adapt as the situation requires.

Oveready is one such manufacturer that has a cross compatible system for their BOSS line of flashlights. On the left is the longer, 18650-tube. You simply swap the head of the BOSS 35 on the right.

There’s no definitive guide to which flashlight you should purchase, but the battery format of your flashlight is undoubtedly one of the most important things you can consider.

As with any purchase decision, you need to ask yourself: What do I need to use X for? Choosing the correct battery format can drastically alter the characteristics and performance of your flashlight.

EDCers who generally don’t have much use for a flashlight, but still want to have something better than the light on their smartphone, will best be served by a 10180 or AAA flashlight. Those trying to fly under the radar will likewise gravitate toward this category of flashlights. Either way, both of these formats will serve you much better than your smartphone’s light.

For those looking for a dedicated EDC flashlight that can be used for a wide variety of tasks, the single CR123a format and 18350 are your best bet.

Finally, EDCers looking for more power and capacity might be best-suited by an 18650 flashlight. Just because the format doesn’t work for me doesn’t mean it won’t work for someone else: I know many EDCers who prefer to carry compact, 18650 flashlights.

I hope this guide helped explain some of the common battery formats with flashlights and what to look for - good luck with your search!