How to Pick the Best 18650 Battery and Charger
Lithium-ion 18650 batteries are a very popular choice for high-power devices that also require long-lasting batteries in terms of capacity, low self-discharge rate, and a large number of charging and discharging cycles.
18650 rechargeable batteries come in countless versions, with many features, some of the most important being capacity, maximum pulse and continuous drain current, charging current, protective electronics, etc.
18650 Battery Dimensions
As its name suggests, 18650 battery dimensions are (diameter x length) 18.6 × 65.2 mm (0.73 x 2.56 inches), or rounded 18 x 65 mm.
Actual dimensions slightly differ from manufacturer to manufacturer, but these small variations in size usually make no problems.
Before buying new 18650 batteries, there are few things to consider.
18650 Battery Features and Specifications
Capacity and maximum discharge current - these two values are closely related since high capacity design limits maximum safe discharge rate and vice versa, high discharge current design limits the capacity of lithium batteries.
For example, high-capacity 18650 batteries have capacities up to and even more than 5000 mAh, but the maximum safe continuous discharge rate of such batteries is often in the 3-10 Amps range.
On the other hand, 18650 batteries being able to provide continuously 20-30 Amps and up to 40-50 Amps for 1-5 seconds safely, such batteries usually have a capacity in the 2500-3000 mAh range.
Note: when promoting their batteries, some manufacturers tend to overestimate the characteristics of their batteries. Thus, it is very important to read reviews and recommendations of other users as well, not just specifications and features provided by manufacturers. Or go for reputable brands and perhaps pay slightly more.
Flat or button positive (top) side - there are two versions of positive (top) side: flat top and button top.
Most of the devices support the use of both types, but just to be sure check the documentation of your device or go for the type that is already working well with your devices - better safe than sorry.
Soldering tabs or not - if you have issues with the 18650 battery pack, replace all the batteries with the new ones that have the capacity and charging/discharging currents in the same range (or better) as old batteries.
Always use the same batteries from the same manufacturer, preferably from the same batch and if you have to solder their tabs, let the professionals solder them for you since it can be a very tricky task to do. Or go for an OEM replacement battery pack, which can cost more, but it is a safer option if you are not absolutely sure what are you doing!
Protected 18650 batteries - since lithium-ion batteries are sensitive to charging and discharging conditions, their temperature, and other parameters, some 18650 models come with built-in protective electronics, which monitor the parameters of the battery and if required, protect the battery by shutting it off until conditions are changed.
Protective electronics require some space and thus slightly decrease the capacity of the batteries - IMHO, more than a worth feature, unless your device already has some sort of battery monitoring function.
Rewrapped batteries - some manufacturers buy cheap 18650 batteries, wrap them as their own and sell on the market, sometimes with highly exaggerated claims regarding their capacity and currents. On the other hand, reputable sellers like Panasonic, Samsung, LG, Sony, etc. thoroughly test their batteries and discard the bad ones. Of course, batteries from such brands cost more, but in the long run, their batteries are actually cheaper.
The following table lists few high quality 18650 batteries with their most common features:
|Model||Capacity||Max. Continuous Current||Comment|
|LG HD2||2000 mAh||30 A||Strong, decent capacity|
|LG HE4||2500 mAh||20 A||Nicely balanced battery|
|LG HB6||1500 mAh||30+ A||Very powerful battery|
|LG HG2||3000 mAh||20 A||Strong and good capacity|
|Panasonic NCR18650B||3400 mAh||6.8 A (12 A, 5 sec)||For low current devices|
|Samsung 25R||2500 mAh||20 A (30 A)||GOLDEN STANDARD :)|
|Samsung 30Q||3000 mAh||15 A||Can go up to 20A, but ...|
|Sony VTC4||2100 mAh||30 A||Strong, decent capacity|
|Sony VTC5||2600 mAh||20 A||Nicely balanced battery|
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Samsung INR18650-25R 18650 2500mAh Battery
Samsung INR18650-25R 18650 2500mAh or for short Samsung 25R is golden standard regarding high power 18650 batteries. It has a high maximum continuous current of 20 Amps and many people have pushed it to its limits draining it with 30-40 or even more Amps (obviously, not recommended).
Its capacity of 2500 mAh at first looks modest, but if you take the higher capacity battery and drain it with 15-30 Amps, the actual capacity will be decreased, just like the number of charging and discharging cycles.
For low current devices, Panasonic NCR18650B features 3400 mAh capacity and it is able to provide almost 7 Amps (6.8 Amps, to be correct) safely.
Over time, manufacturers improve their designs and new batteries come with larger capacities and larger supported drain currents, but these batteries in the list have been tested in real-life applications countless times.
IMR, INR, IFR, or ICR 18650 Batteries
Labels of 18650 batteries often include abbreviations like IMR, INR, IFR, or ICR. These abbreviations describe actual battery chemistry:
- IMR 18650 batteries feature LiMn204 (Lithium Manganese Oxide) chemistry. Their nominal voltage is 3.6 - 3.7 V per cell, with a maximum recommended charging voltage of 4.2 V. IMR batteries commonly have a smaller capacity but are capable of delivering larger currents.
- INR 18650 batteries feature LiNiMnCoO2 (Lithium Manganese Nickel) chemistry. These batteries are very similar to IMR batteries since they can provide plenty of currents, with slightly lower capacity.
- IFR 18650 batteries feature LiFePO4 (Lithium Iron Phosphate) chemistry. Their nominal voltage is 3.2 - 3.3 V per cell, with the maximum recommended charging voltage of 3.5 - 3.6 V.
- ICR 18650 batteries feature LiCoO2 (Lithium Cobalt Oxide) chemistry. Their nominal voltage is 3.6 - 3.7 V per cell, with the maximum recommended charging voltage of 4.2 V. They commonly have higher capacities, but maximum allowed currents are often limited to just a few C.
Note: there are other chemistries on the market too, including hybrid technologies like Lithium Nickel Cobalt Oxide (LiNiCoO2), Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO2), etc.
18650 Battery Chargers
Modern 18650 battery chargers are intelligent battery chargers that can sense the battery type, chemistry, condition, etc.
Often these battery chargers can be used for charging a broad range of batteries, including NiCd, NiMH, and various lithium rechargeable batteries.
The most important features of intelligent battery chargers include:
- number of slots (number of charging batteries),
- charging currents and modes, including battery test, maintenance mode, full discharge, trickle charging, and similar,
- accepted battery sizes and chemistries, etc.
When choosing a battery charger for your needs, pick a battery charger according to your current, but also future needs, too.
18650 Batteries With USB Built-in Charger
To simplify the charging of 18650 batteries, some models feature a built-in USB battery charger - when charging is required, the battery is simply connected to a USB port, and onboard electronics monitor battery parameters and do all the work.
These models are highly recommended for people needing just a few 18650 batteries for their devices.
Although built-in USB battery chargers require some space and thus decrease the battery capacity, they also often monitor battery condition during operation and protect it, if required.
18650 Battery Equivalents
When replacing the 18650 battery, the best option is to use another 18650 battery with the same, preferably better characteristics.
However, some devices allow the use of other batteries, like 3xAAA batteries, 2xCR123A batteries, and similar.
- 16650 battery is slightly narrower than the 18650 battery, but some devices accept this battery even without a plastic 'sleeve' where it can be inserted and placed onto the 18650 positions just as any normal 18650 battery. Due to the smaller dimensions, 16650 batteries often have lower capacities or smaller allowed currents.
- 17670 battery is also slightly narrower than the 18650 battery, but it is also somewhat longer and not all devices can accept it due to its length - check the device's documentation before replacing the 18650 with a 17670 battery.
- 19670 battery is slightly wider and longer than the 18650 battery and again, not all devices can accept it due to its dimensions - again, check the device's documentation before replacing the 18650 with a 19670 battery. Note: 19670 batteries generally feature larger capacity and/or allowed currents. Also, some manufacturers advertise 19670 batteries with protective electronics as 'protected 18650' batteries. For short: nice battery, just check if your device can accept it.
- CR123A batteries are roughly half the length of the 18650 battery (17.0 x 34.5 mm vs 18.6 x 65.2 mm). Some devices are designed to operate regardless of the 3-4 mm difference between 2xCR123A and one 18650 battery.
Also, the CR123A battery is available as a non-rechargeable lithium battery providing 3.0 V and as a rechargeable lithium-ion battery (often designated 17340, 17345, or 16340 battery) providing 3.6 - 3.7 V.
This difference in voltage (3.6 vs 6 vs 7.2 volts) can damage many devices and one must check the documentation of a particular device to be absolutely sure if 2xCR123A batteries are supported.
Note: non-rechargeable lithium CR123A batteries from reputable brands have a shelf-life of often 10 or even more years and even after 10 years, they can provide large currents easily. Thus, CR123A batteries are often recommended for standby devices like EDC flashlights, panic lights, and similar devices that are often not used for years, but when they are used, they must operate reliably.
- 3xAAA batteries can be used instead of one 18650 battery in certain devices via an AAA battery holder.
For devices that are often used, a rechargeable 18650 battery is recommended choice. But for standby applications, 3 high-quality AAA batteries (alkaline batteries, not rechargeable NiCd or NiMH batteries) are a more reliable choice.
Even if you have rechargeable NiCd or NiMH AAA batteries, do yourself a favor and get one good 18650 battery with a built-in USB charger - such a battery will easily outperform 3xAAA batteries and it can withstand more charging/discharging cycles.
18650 Battery Flashlights
18650 batteries are commonly used as high-power and high-density energy sources for LED flashlights, ranging from compact EDC flashlights to strong and powerful tactical flashlights.
18650 flashlights usually feature one to two 18650 batteries, rarely more - only high-output, very bright flashlights feature three, four, or even more 18650 batteries.
Since LED flashlights use a built-in LED electronic management system, some 18650 LED flashlights allow the users to use either 18650 batteries, CR123A batteries, or AA batteries.
As said before, two CR123A batteries may replace a single 18650 battery, which is recommended for EDC flashlights that are rarely used but must operate reliably even after years of storage.
In order to provide the highest possible IPX waterproof and dustproof rating, some 18650 LED flashlights use various USB magnetic charging cables, allowing the batteries to be recharged without any openings on the battery's body.
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18650 Battery vs 26650 Battery
18650 and 26650 batteries share the same length, but the 26650 battery is wider and has some ~2x larger volume.
Thus 26650 batteries are often used in devices requiring even more power and energy - 18650 battery packs plenty of energy, but 26650 packs on average 2x more.
18650 battery can be used instead of 26650 battery using a special battery holder, just be sure that 18650 battery can provide enough current for that particular device.
IMHO, 18650 batteries are great, but if your device supports the use of 26650 batteries, go for 26650 batteries.
For short: the best battery replacement for a 18650 battery is another 18650 battery - plain and simple. When choosing new batteries, consider your old batteries and the device(s) you have, and their requirements.
Note: never, but really never charge lithium batteries with chargers not designed for such batteries. Also, never throw them in fire, leave them in the hot car, or similar. And, after they served you well, dispose of them properly (they can be almost 100% recycled!).