Flashlight Batteries: 18650 Batteries vs AA

When you go camping or hiking you are effectively off-grid and the essentials of daily living become all that more important. Power is a big one. The modern era offers hundreds of solutions to maintain the relative comforts of home even when you’re ten miles deep in the bush. Not all of these solutions are made equal though nor are they all appropriate for every situation.

Flashlights, and the means of powering them, have become a focal point for this. Battery technology has changed rapidly and the options that were once available have broadened immensely. Making the right choices in this expanding field can make the difference between a flashlight that guides you back to camp and a night spent wandering in the dark.

A man standing on a rock in the fog with a flashlight.

A good flashlight or light source like a headlamp can keep you safe, especially in the dark.

The classic, and misleading, 18650 battery vs AA battery debate

Out of the many batteries and power options available a small, and mostly unwarranted, rivalry has arisen. People are asking whether it is better to power their flashlights and other camping gear with 18650 batteries or with AA batteries.

The plain and simple answer to that is that any device should only be powered with the battery suggested by the manufacturer. We will get into that more but the main reason for this has to do with the fact that different batteries give off different amounts of electricity at different rates. When the wrong battery is in your device it can cause the battery to overheat and when that happens the battery can leak, damage your device, or even explode! 

The labels “18650” and “AA” technically just refer to different battery sizes. The key distinction is that the 18650 is specifically a size for a rechargeable lithium-ion battery while AA can be zinc-carbon, alkaline, nickel-cadmium, nickel-metal hydride (NiMH), or even lithium-ion among others. The 18650 lithium-ion batteries are 18mm x 65mm in size, hence the name. AA’s of any kind are approximately 14mm x 50mm in size so an AA lithium-ion battery might also be called a 14500. 

As you can see, when sizes are given in letters like AA, AAA, or D for example that refers to a wide class of battery types all of which have the same general size. When sizes are given as five digits like 18650 or 14500 that refers to rechargeable lithium-ion batteries specifically. This means that any conversation comparing or contrasting 18650 batteries with AA’s is a bit like comparing apples to oranges. 

The questions then become which battery is better for camping and what kind should you put in your flashlights. If cost isn’t an issue, then the short answer to those questions is that, compared to AA’s, the 18650’s win every time. You can’t just run out and immediately replace all your AA’s with 18650’s though. Do not do that! As mentioned previously you have to use the battery type recommended by the manufacturer. This means you will need equipment designed to use the 18650’s. Another important consideration is that not all 18650’s are made equal. Counterfeits are not uncommon and you have to know what to look out for. 

Super Bright 2000 Lumen 18650 Tactical Flashlight and 6PCS 3.7V 9900mAh Rechargeable Battery+Batteries Charger,Zoomable, Water Resistant, 5 Modes Handheld Flashlight
  • SUPER-BRIGHT: 2000 lumen (max) LED Flashlight,Ultra wide beam effortlessly illuminates a whole room or backyard.Adjustable focus with 5 modes: High, Medium, Low, Strobe, and SOS/Emergency protect your...

The ins and outs of a 18650

The 18650 battery cell is an 18mm x 65mm rechargeable lithium-ion cell and it has become the go-to standard in a wide array of tech. Flashlights, smartphones, cameras, you name it. These batteries typically put out around 3.7 volts with a capacity ranging from 1800 mAh up to 3500 mAh.

For all the non-techies out there, mAh stands for milliamp-hour and it is a unit that measures how much electrical power is put out over time. The higher the mAh the longer the life of the battery. The volts, or voltage, on the other hand, is how much electrical ‘push’ or power the battery can generate. More voltage means the battery is putting out more power. 

When you combine a higher voltage with higher mAh in a rechargeable battery you get more power over a longer time period that you can reuse again and again. AA batteries, by comparison, have a wide range of mAh stats depending on the underlying cell type. Most AA’s sit at about 1.2-1.6 volts for the non-rechargeable batteries while the rechargeable ones can be around 3.7 volts. Still, even the 14500 (“AA” sized) rechargeable lithium-ion at 3.7 volts does not have the same capacity as a 18650. 

The size difference explains it all. The 18650 is a bigger battery that can put out more electrical charge over time. You can get very technical with all of this if you want and there is seemingly no end to what you can learn about batteries. If you want to go a step further to really be sure the battery you have suits the device you want it to you can also check something called the continuous discharge rate (CDR). 

This is a measure of how quickly a current can be pulled from the battery and it is displayed in Amps (A). Basically, the current output of the battery has to match to the power draw of the device. If this is mismatched that is when bad things happen. Harmful battery leaks and explosions are the results. 

A globe indicating a map of China.

For all its beauty mainland China has also been the source of many counterfeit batteries.

Battery boundaries: what to look out for 

The 18650 batteries, and the required charger that goes with them, are understandably pricier than your typical non-rechargeable AA battery. One 18650 battery can cost double that of a regular AA. This difference is only a couple dollars but the profit margins on enough sales were adequate to spur a ring of counterfeit batteries pouring out of places like China and Malaysia. At best buying one of these batteries is a nuisance and at worst they can explode and seriously injure you. 

When you consider the continuous discharge rate of some of the best 18650’s available you will see something around 38A at 2000 mAh. That’s impressive enough but also feasible. The counterfeit batteries have been seen with claims that just aren’t realistic. Although battery technology is constantly changing and evolving it is important to understand there are limits. Typically a higher amperage (A) means a lower capacity (mAh) for the battery to run safely. The inverse holds true as well.  

If you’re looking at a 18650 with specifications around 40 A with over 2000 mAh you should be suspicious. Do your research. As a measure of feasibility, the higher 3500 mAh 18650 batteries should draw closer to 8A, not 30A! Sony, Samsung, LG, and Panasonic are some of the bigger and trusted brands in the industry. If you’re looking to buy a 18650 battery set you should go through one of their sites. Just seeing the brand name isn’t a sign of security though. 

Counterfeiters have gotten really good at replicating the batteries of other brands and then selling them through third-party vendors like Amazon. Another way to discern the real from the fake is by weight. Using spec sheets from the sites of reputable manufacturers you can see how much a certain 18650 should weigh. The counterfeiters are cunning but, due to shipping costs and requirements, they sometimes put accurate battery weights in their listings. The wrong batteries won’t match up. 

Protected or unprotected, flat top or button top?

The many benefits of rechargeable lithium-ion batteries also come with a nearly exhausting variety of options. When buying 18650 batteries you will notice that some are labeled protected and others are labeled unprotected. From the standpoint of a functioning and rechargeable battery, you can get either one and be on your way. From the standpoint of value and safety though you should get a protected battery. 

The protected cell has circuitry built-in which protects the battery and the device it is in from overcharging and overheating. A high capacity battery stuck in your camping flashlight during your hike across a blisteringly hot desert is very much at risk. This goes for any battery. Protected 18650’s have a built-in insurance policy though. Protected batteries are more expensive than unprotected ones but the tradeoff is nearly negligible given the benefits.  

You might also find batteries listed as flat top or button top. This refers to the shape of the positive contact point on the battery. A flat top is flat as you’d expect and the button top protrudes like a button. In some devices knowing the difference is important so you’re sure the battery you get will fit. For most flashlights, it isn’t that big of an issue given they often have springloaded battery chambers. 

These differences all add to the importance of following manufacturer specifications. If you have invested in a nice flashlight that is compatible with 18650 batteries but you still need to buy the batteries then the instructions or manufacturer should be able to easily provide the details of what you need.

A person under the stars at night with a flashlight.

When it’s just you, a flashlight, and nature you’ll be glad you got the right equipment.

Choosing a flashlight and battery 

Super Bright 2000 Lumen 18650 Tactical Flashlight and 6PCS 3.7V 9900mAh Rechargeable Battery+Batteries Charger,Zoomable, Water Resistant, 5 Modes Handheld Flashlight
  • SUPER-BRIGHT: 2000 lumen (max) LED Flashlight,Ultra wide beam effortlessly illuminates a whole room or backyard.Adjustable focus with 5 modes: High, Medium, Low, Strobe, and SOS/Emergency protect your...

Gearing up for hiking or camping is an adventure unto itself. There are many options. Choosing the right flashlight, and its required batteries can just add to the complexity sometimes. Much of it comes down to personal needs and preferences. Years of camping and hiking do reveal a few key things to look for though. You want a flashlight that is bright, lightweight, waterproof, durable, and longlasting. One with a red light mode and a strobe is even better.  

Any good LED camping flashlight should tick off these boxes. Some that take AA’s and other non-rechargeable batteries are just fine and sometimes they are even preferred. The big downside of rechargeable batteries is that you have to charge them. If you only have one and it loses charge then you can end up in a tight spot. Also, if you don’t expect to be near a charging point for a while that can cause problems. 

With rechargeable batteries as your primary source of power you just have to plan things out. Finding a charging spot, or bringing something with you like a solar setup, is still better than carrying a supply of batteries in your pack. Two or three rechargeable batteries can cover all your needs for years instead of saddling yourself with a pack of one-off batteries. 

The ideal camping flashlight would be a fully rechargeable, dimmable, LED flashlight capable of something around 1000 lumens at the upper end. Keeping that waterproof (this means IPX8 and above), durable, and lightweight would be best. These types of flashlights usually come with 18650 or 14500 rechargeable batteries. 

If the flashlight you own seems to fit the bill but only has one rechargeable battery then you should go ahead and buy two more of the same battery. The best way to do this is to order directly from the manufacturer and short of that use the manufacturers’ specifications to find the same battery elsewhere. This extends to all light sources you plan to bring with you. So lamps, headlamps, flashlights, they should all have backup batteries which are fully charged and ready to use. 

If you do order backup batteries you should test them before hiking or camping. Charge them up, let them sit, then use them. Do this a couple of times if you can. A 2 a.m. bathroom break in the woods is not the best time to find out your battery is a counterfeit or can’t hold a charge. 

What about CR123A?

In the world of flashlight batteries, there are some key players. You have the “A” class of batteries like AA and AAA which can also include the rechargeable 14500 for good measure. Then you have the popular 18650 as a higher capacity rechargeable lithium-ion. Then you have the CR123A. These three battery families are the most common forms of power for camping flashlights. 

The CR123A is a 17mm x 34.5mm battery averaging a nominal voltage around 3.0 volts and a capacity of 1500 mAh for the non-rechargeable version. Much like the AA’s this battery comes in a chargeable form, known by 17340 or 17345, that sits at 3.7 volts and having a capacity around 800 mAh on the high end. These batteries are roughly half the length of the 18650 so they pack half the capability more or less. Often they come as a pair to up the lifetime for the device in question.   

One 18650 can stand in for two CR123A which in turn can take the place of 3 AAA’s. As far as price, size, power, and reusability go the 18650 seems to be your best bet. One interesting advantage of a flashlight that runs on CR123A’s though is its relative rarity. During hurricanes or other disasters when almost every battery type is sold out you still might have some luck finding an extra CR123A on a shelf somewhere. 

Different batteries for different purposes

Outside of the scope of camping, flashlights are used in many scenarios. Some flashlights are used on a daily basis and this is known as everyday carry (EDC). Other flashlights are set aside as part of an emergency kit. 

Any EDC light should definitely run on rechargeable batteries. This saves time and money over the long term. For lights that are stowed aways, such as in emergency packs, you want lithium batteries for sure. These have a good shelf life and a very low discharge rate so they will be ready to go even after years of inactivity. It is also helpful to have a flashlight that runs on common AA or AAA batteries just in case.   

A person in the middle of the road, holding a flashlight under the stars.

A reliable power source adds another layer of needed assurance for any excursion.

Final Verdict:

At times it can seem like the progressive march of technology is outpacing the ability to keep up with it. At one point in time, flashlight and battery pairings were more straight forward but innovation has changed that. Advancements in chemistry have opened the door for rechargeable batteries with lithium-ion (Li-ion), nickel-metal hydride (NiMH), and nickel-cadmium (NiCd) being the most common. Although the technology is imperfect at times with battery explosions and leaks making headlines it is still the state of the art.

When possible it is certainly best to have the best technology working for you when you are camping or hiking. The old classics like alkaline batteries are falling far behind the benefits of li-ion batteries so it pays for the modern outdoors aficionado to stay up to date. The differences are worth it.  

Bonus Tip: Watch how one expert tests 18650 cells and learn more about this excellent power source!

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Riley Draper

Riley Draper is a writer and entrepreneur from Chattanooga, Tennessee. As a world traveler, he has been to more than fifty countries and hiked some of the most elusive trails in the world. He is the co-founder of WeCounsel Solutions and has published work in both national and global outlets, including the Times Free Press, Patch, and Healthcare Global. When he's not writing, he's probably on a hiking trip or climbing in the mountains.