18500 Battery Equivalents and Replacements
18500 batteries are lithium-ion rechargeable cylindrical batteries, slightly smaller than the more popular 18650 batteries, and are commonly used in game controllers, LED flashlights, medical and security applications, solar lights, etc.
18500 batteries differ in shape, especially top battery terminals and internal construction. Also, they tend to differ slightly in height, requiring users to be careful when buying these (and other) cylindrical lithium batteries.
Published: February 10, 2023.
18500 Battery Features and Specifications
18500 lithium rechargeable batteries feature nominal dimensions of (D x H) 18 x 50 mm (49.8 mm), with a nominal voltage of 3.2-3.7V (mostly 3.6-3.7V) and capacity in the 800-2100 mAh range.
Solar 18500 batteries are generally based on the Lithium Iron Phosphate (LiFePO4) chemistry and feature a nominal voltage of 3.2V, capacity in the 800-1200 mAh range, can tolerate wide temperature range, and support a large number of charging/discharging cycles.
Lithium-ion 18500 batteries feature a nominal voltage of 3.6-3.7V, charging voltage of up to 4.2V, and capacity in the 1000-2000 mAh range, with some models claiming a capacity of up to 2300-2400 mAh.
Generally, high-drain lithium-ion batteries have a smaller capacity and vice versa, higher capacity batteries are intended for low(er)-drain applications.
Protected vs. Unprotected 18500 Battery
Like any lithium-ion battery, 18500 batteries are sensitive to charging/discharging conditions, including current, voltage, and temperature.
Battery Management System (BMS) is added to 18500 batteries to protect (hence "Protected 18500 Batteries") the battery from unwanted events that may harm the battery in any way.
Such protected batteries are much safer than unprotected 18500 batteries, although they may have somewhat lower capacity than unprotected versions.
But, in order to keep the capacity and desired level, some manufacturers tend to make protected 18500 batteries a few millimeters longer, up to 52-53 mm, and such "longer" 18500 batteries sometimes cannot fit standard 18500 battery compartments.
For short, when buying a 18500 battery, especially a protected 18500 battery, check the battery's actual length.
Flat Top vs. Button Top
18500 batteries have two types of positive terminals, flat top, and button top, just like many other lithium-ion batteries, for example, 18650 batteries.
When looking for a new 18500 battery, always check what type of positive terminal your old batteries have.
Also, some battery compartments support the use of both flat-top and button-top batteries, simplifying getting new batteries.
How To Charge 18500 Batteries
18500 batteries should be charged using dedicated lithium-ion battery chargers that support CC/CV (Constant Current/Constant Voltage) charging algorithm optimized for lithium-ion batteries.
Fortunately, many battery brands offer such battery chargers that can be used for charging cylindrical lithium-ion batteries - most battery chargers intended for, for example, 18650 batteries can be used to charge 18500 batteries as well.
Note: just in case, read the Owner's Guide of the battery charger and verify if it is safe to charge 18500 batteries with it.
18500 Battery vs. 18490 Battery
18500 and 18490 batteries are very similar, practically the same batteries, differing only in 1 mm (0.03937 inches) in height.
Since many 18500 and 18490 batteries differ in size from their official dimensions, some 18500 batteries may be closer to 18490 official dimensions, and some 18490 batteries may be closer to 18500 official battery dimensions.
Whenever getting a new battery, it is always a good practice to check the battery's actual size, just in case...
18500 Battery vs. 18650 Battery
18500 batteries and 18650 batteries have similar dimensions:
- 18500 battery: 18 x 50 mm,
- 18650 battery: 18 x 65 mm.
Practically, 18500 batteries are "shorter" 18650 batteries, and since they are both based on the same chemistries, they have somewhat lower capacities.
18650 batteries are much more popular, but 18500 batteries are more compact and are often used in devices that require smaller batteries than 18650 batteries.
18500 Battery vs. AA (14500) Batteries
18500 batteries and AA (14500) batteries have similar dimensions:
- 18500 battery: 18 x 50 mm,
- AA (14500) battery: 14.5 x 50.5 mm.
Lithium-ion AA batteries, also known as 14500 batteries, have a length very similar to 18500 batteries, but they are narrower and, as such, have a smaller capacity.
Some brands offer special battery holders that allow 14500 batteries to fit into the 18500 battery compartments, which may simplify powering of their devices.
But, as said before, 14500 batteries have a smaller capacity than 18500 batteries and will not last as long as 18500 batteries will.
Long Story Short: 18500 batteries are not the most popular cylindrical lithium-ion batteries, but they can be nonetheless easily found in local hardware stores and online shops.
When buying new 18500 batteries, be sure to check the batteries' actual dimensions, check if the battery is protected or not, and check the positive battery terminal (flat-top or bottom-top).