Headlamp Battery Size Comparison: AA Vs AAA Vs Ni-MH Vs Li-ion

Last Updated on 02/01/2022

Headlamp Battery Size Comparison

Headlamp Battery Size Comparison: 14500 Li-ion Vs AA Vs Ni-MH Vs AAA Vs 10440 Li-ion

Knowing your headlamp battery size and type is vital when selecting your new lamp. Before purchasing your flashlight, select whether you want to be using disposable or rechargeable batteries, as well as the type of battery itself. Certain batteries perform better in different climates, while others hold their intensity for longer.

There’s a good chance that when you look at the specifications of your new backpacking headlamp, the batteries are the last thing you worry about. Different types of batteries perform to different standards, though. Some are brighter, or discharge themselves less over time, while others work better in cold conditions.

If you have an idea of the type of battery you want to use, you should check that your preferred lamp will support them. While the sizes are similar among different styles, they can have varied output ratings, which may overload your lamp. Cavers headlamps for example typically have much larger batteries and outputs wheres a trail running headlamp priorities lightness and compactness.

At the end of their life, many batteries can be recycled. Others may have to be disposed of in certain ways. You should check locally the best ways to dispose of your batteries, once they are no longer of use.

What You Need to Know About Headlamp Batteries

  • Most Headlamps will either take 2 x AA, 3 x AAA, or have some kind of Lithium Ion rechargeable battery.
  • The benefit of headlamps being compatible with disposable batteries is that you can always carry spares and buy them worldwide.
  • The benefits of using rechargeable headlamp batteries is that they have longer lives, are more environmentally friendly, cost effective, and can be charged with a power bank.
  • Check the batteries in your headlamp for the size you need to replace them. If your don’t know what batteries your headlamp needs and AA or AAA batteries don’t fit then you can try look up the manufacturer model online. There may also be some writing inside the battery housing t o tell you what size headlamp battery you need.

Common Headlamp Battery Sizes

This is where things might start to get technical. We’re going to look at different types of batteries, their sizes, output, and how they are used. This is just an overview of sizes for now, but we’ll come to different styles shortly.

AA Batteries

Duracell - CopperTop AA Alkaline Batteries - long lasting, all-purpose Double A battery for household and business - 24 Count

AA Batteries, or ANSI Type 15 batteries, are perhaps the most common household battery style in the US. These are around 1.99 in. (50.5 mm) long and have a diameter of 0.57 in. (14.5 mm). These are your standard, cylindrical batteries with a small positive terminal button on the top.

AA batteries tend to have a power output of around 1.5 volts. The capacity of AA batteries varies dependent on battery style but can range from around 1000 mAh to around 3000 mAh. This means that the battery life of your AA headlamp can vary enormously, too.

Most headlamps that use AA batteries require between 2 – 4 batteries. This depends on the voltage demands of the bulb.

AAA Batteries

Duracell - CopperTop AAA Alkaline Batteries - Long Lasting, All-Purpose Triple A Battery for Household and Business - 24 Count

AAA, or ANSI Type 24, batteries are probably the most common style of batteries in modern LED headlamps. AAA batteries are 1.75 in (44 mm) long and have a diameter of 0.41 in. (10.5 mm). As with AA batteries, these look like your recognizable, household battery, with a protruding positive terminal on top.

AAA batteries also have a power output of 1.5 volts. However, compared with AA batteries, AAAs have a far lower run-time. The standard capacity of a AAA battery is between 500 – 1200 mAh.

Headlamps that use AAA batteries rarely require fewer than 3, with most taking 4 or more.

18650 Lithium-Ion Batteries and Bigger

With headlamp battery size, there is generally a safe assumption that bigger is better, in terms of run time at least. You should, however, be aware of overloading your headlamp. Using a battery with too high a voltage will cause your headlamp to burn out, or at the very least, it will affect its lifespan.

The number on a lithium-Ion battery is directly related to the size. For example, a 18650 battery has a diameter of 18 mm (0.71 in) and a length of 65 mm (2.55 in.). These batteries, a little larger than a standard AA battery, usually give off around 3.7 volts and have a capacity of 1500 – 3500 mAh.

Most headlamps won’t go above a 18650 battery. Larger batteries come with a higher associated weight and it becomes more difficult to design a headtorch that won’t slide down with the weight.

Most of these larger battery packs, and some smaller styles, have rear-mounted battery packs to prevent the weight from pulling down your headlamp. These are not uncommon with smaller batteries, too.

AAA Disposable44.5 mm10.5 mm1.5
AAA 10440 Li-ion Rechargeable44.5 mm10.5 mm1.5 - 3.7
AAA Ni-MH Rechargeable44.5 mm10.5 mm1.2
AA Disposable50.5 mm14.5 mm1.5
AA 14500 Li-ion Rechargeable50.5 mm14.5 mm1.5 - 3.6
AA Ni-MH Rechargeable50.5 mm14.5 mm1.4
18650 Li-Ion Rechargeable65 mm18 mm3.7
CR123A Disposable Batteries34.5 mm17 mm3.7

Different Types of AA Headlamp Batteries

There are three main types of AA headlamp batteries available. These are disposable, li-ion rechargeable, and Ni-MH rechargeable. In this section, we’re going to have a look at what makes each type stand out and why you would choose one, not the other.

AA Disposable Batteries

Duracell - CopperTop AA Alkaline Batteries - long lasting, all-purpose Double A battery for household and business - 24 Count

AA disposable batteries are probably the most common battery that you will see anywhere in the world. If you are traveling and need to replace your headlamp batteries, there’s no cheaper choice than disposable, alkaline batteries.

These are not the choice of the environmentally conscious, but a choice of convenience. Alkaline batteries have a low level of self-discharge, so they last a long time in storage or unused. They do tend to leak, though, so it can be better to store them outside of your torch if you don’t plan to use them.

Alkaline batteries discharge quickly compared with lithium-ion batteries. The discharge graph of an alkaline battery drops quickly then slows, but with a lower output. They also tend not to work as efficiently in extreme temperatures.

14500 Li-ion Rechargeable Batteries (AA)

Deleepow Rechargeable AA Batteries, 1.5V 3200mWh Lithium Rechargeable AA Batteries, Long Lasting Double A Battery, 1500 Cycles, 4-Pack

If you want to use a 14500 Li-ion battery then make sure it has a voltage output of 1.5 volts and is specified as AA compatible. Standard 14500 Li-ion batteries are a slightly different sizes to universal AA batteries so this is important to get right.

Li-ion batteries are rechargeable and do not have a memory. This means that they can be safely charged without being fully depleted and there will be no long-term effects on the capacity. The rechargeable nature of these batteries means you need to have your charger with you and be sure of a stable source of power.

Li-ion batteries perform well in extreme conditions, making them a popular choice for cold climates. Li-ion batteries are prohibited in checked baggage as they have been known to explode with unstable pressure.

Ni-MH Rechargeable Batteries (AA)

Tenergy Premium PRO Rechargeable AA Batteries, High Capacity 2800mAh NiMH AA Battery, 12 Pack Rechargeable Batteries

Nickel-Metal Hydride rechargeable batteries are excellent all-around rechargeable batteries. Ni-MH batteries have a slightly lower voltage but are usually compatible with headlamps.

Ni-MH batteries are more stable than both alkaline and Li-ion batteries. They aren’t prone to leaking or exploding but can be traveled safely.

The shelf life of a Ni-MH battery is shorter, though, and they can be prone to battery memory. This is the effect of your battery life shortening over time from partial charging. Ni-MH batteries are also prone to a higher rate of self-discharge than other styles of battery.

Different Types of AAA Headlamp Batteries

AAA battery powered headtorches are the most common for the cheaper headlamps. The three main types of AAA batteries are similar to the types of AA batteries and therefore have similar qualities.

AAA Disposable Batteries

Duracell - CopperTop AAA Alkaline Batteries - Long Lasting, All-Purpose Triple A Battery for Household and Business - 24 Count

AAA disposable batteries can be bought just about anywhere in the world. If you have a headlamp that won’t take disposable batteries, it is probably worth making sure that your spare will. That way, you can always have access to a lamp, no matter where in the world you are.

The low self-discharge rate makes these batteries a good choice if they are going to remain unused inside your headlamp. However, they are prone to splitting and leaking, though, so long term should be removed.

10440 Li-ion Rechargeable Batteries (AAA)

AAA ICR 10440 Rechargeable Lithium Ion Battery,3.7v 350mah 4pcs

The 10440 Li-ion rechargeable batteries will fit most AAA-rated headlamps. It is still worth checking with the manufacturer’s guidelines, though, before changing your original AAAs out for some 10440 batteries.

Li-ion batteries have a powerful discharge and remain at high power throughout their cycle. They also do not suffer from battery memory and can be recharged at any point through their cycle, without negative lasting effects.

Li-ion batteries are not permitted in hold luggage as they are prone to exploding. If you are traveling with your headlamp, you should check that it is in your hand luggage before boarding.

Ni-MH Rechargeable Batteries (AAA)

Tenergy Premium PRO Rechargeable AAA Batteries, High Capacity 1100mAh NiMH AAA Battery, 24 Pack Rechargeable Batteries

Nickel-metal Hydride batteries usually have a lower voltage than other AAA batteries. This is usually around 1.2 V. Though this is lower, they usually still offer enough voltage for a headlamp.

These batteries have a quality, powerful discharge, but a shorter lifespan than others. They self-discharge at a higher rate and aren’t suited to being stored long-term in your headlamp. They can also suffer from battery memory, limiting the overall capacity if charged from partial depletion.

Ni-MH batteries are more stable than alkaline or Li-ion batteries, though. They aren’t prone to either exploding or leaking.

Different Li-ion Headlamp Battery Sizes 18650 and Higher

Li-ion headlamp batteries are considered to be the most efficient rechargeable batteries on the market. The larger the battery, the longer your battery will usually last. Larger batteries also tend to come with a higher output and can be used with more powerful headlamps.

These larger batteries will take far longer to charge, though. They are also far heavier. Weighty headlamp batteries can make your headlamp bounce, or even slide down over your eyes, especially if it doesn’t have a separate, rear-mounted battery pack.

18650 Li-Ion Batteries

20 PCS 18650 Li-ion Rechargeable Battery 3.7V 6000Mah 18650 Li-Ion Battery Large Capacity Cylindrical Button/Niple Top for LED Flashlight Torch Headlam

These are a particularly popular choice of batter in headlamps and flashlights because of the amount of power they carry. Their particular mAh will vary between models and are usually between 1500 – 3000 mAh.

Although lithium-ion batteries do last far better in the cold than other styles, 18650 batteries performance becomes sub-optimal in freezing temperatures. Because these

CR123A Disposable Batteries

Panasonic BAT002 x 2 CR123A Lithium 3V Photo Lithium Batteries, 0.67" Dia x 1.36" H (17.0 mm x 34.5 mm), Black, Gold, Blue (Pack of 2)

CR123A disposable batteries are among the best batteries available for use in sub-zero temperatures. These are non-rechargeable lithium batteries with an extremely long shelf life. CR123A batteries can last up to ten years in simple devices like solar lights and cordless phones. In a headlamp, they will be used much faster.

CR123A batteries are 1.35 in. (34.2 mm) tall and have a diameter of 0.67 in. (17 mm). Their usual voltage is between 3.2 – 3.3 V and they have a capacity of around 1550 mAh.

CR123A Rechargeable Batteries 16 Pack with Charger, Rechargeable Lithium Batteries [ 750mAh 3.7V ] for Arlo Cameras (VMC3030/VMK3200/VMS3330/3430/3530), Flashlight

Rechargeable CR123A Batteries

What Type of Headlamp Battery Size is Best?

Although the initial outlay is higher, you will save money in the long run with rechargeable batteries. There is an environmental benefit, too. The less you can add to landfills, the better.

Lithium-ion batteries are the best kind of rechargeable battery and the most powerful of these is the 1450 model. One of the key benefits of a lithium-ion battery is that it doesn’t drop on power as quickly, but maintains a high output throughout its discharge.

How Long Does it Take to Charge a Headlamp Battery?

Estimating the charging time for your battery is depended on what amperage you charge at. Most battery chargers trickle their feed, with an amperage of between 120 – 150 milliamps.

Some chargers have fast charging options that go up to 500, or even 1000 milliamps. This may be good in an emergency but can damage the long-term life of your battery.

Your charging time is the mAh of the battery, divided by the input. For example, if the mAh of your battery is 1500 mAh and you charge it at an amperage of 500 milliamps, you will require three hours of charging time.

10440 Li-ion Batteries (AAA)

10440 batteries have a mAh of between 250 – 350. These can usually be charged in two to three hours on a trickle charge. If you need these in a hurry, a fast charge can have them fully powered in under an hour.

14500 Li-ion Batteries (AA)

The capacity of a 14500 li-ion battery is around 700 – 1000 mAh. With a trickle charge of 150 mA, these will take four to seven hours to charge. A fast charge can take 1.5 to 2 hours.

18650 Li-ion Batteries

The large capacity of a 18650 battery means it will take longer. The capacity of these is between 1500-3000 mAh and they can easily take 10 – 20 hours on a low trickle charge. Even on a fast charge, you’re looking at around 3 to 5 hours of charging.

Ni-MH Rechargeable AA Batteries

Ni-MH AA batteries have a capacity of 1700 – 2800 mAh. On a trickle charge, these batteries will take between 10 – 18 hours to charge. Fast charging can have these charged in 3 to 5 hours.

Ni-MH Rechargeable AAA Batteries

With a capacity of 800 – 1200, you can charge a Ni-MH AAA battery in around 5 – 8 hours. With a quick charge, these can be ready to go in 2 – 3 hours.

PETZL, CORE Rechargeable Battery for Petzl Headlamps, Compatible with ACTIK, TIKKA and More

Are 18650 Batteries Bigger than AA?

Yes. 18650 batteries are considerably larger than AA batteries and fit different models of headlamps.

Comparatively, AA batteries are 1.99 in. (50.5 mm) long and have a diameter of 0.57 in. (14.5 mm). 18650 batteries have a diameter of 18 mm (0.71 in) and a length of 65 mm (2.55 in.).

They have vastly different output, too. AA batteries are typically 1.5 V and have around 1000 – 3000 mAh. 18650 batteries are usually 3.7 volts and have a capacity of 1500 – 3500 mAh.

How to Recharge Headlamp Batteries

How you recharge your headlamp will depend largely on the design of the model itself. Many headlamps that have lithium-ion batteries are designed for them to be charged in place. These usually come with a special charging cable and can be plugged directly into an outlet.

If your battery pack is designed for you to remove the batteries for charging, you will need to use a specialist battery charger. These vary in quality, as well as in which batteries they are compatible with.

You should always check manufacturer guidance when it comes to charging batteries and using charging devices. Poorly maintained or inappropriately charged batteries can be dangerous to use and store.


Gear Assistant
Gear Assistant

This article has been written and/or edited by Andrew N. 20+ years of hiking, mountaineering, and camping experience, with access to all the latest outdoor gear.

Gear Assistant