Today it seems like almost everything takes a battery in order to work. But when we get into more specialized equipment we find that the classic AA and AAA batteries won’t cut it. And we are left wondering which batteries to use in our equipment.

This is certainly true for tactical gear and other specialized tools when we see battery styles like the CR2 or the CR123. But what’s the difference between these batteries and how should they be used?

The Difference Between CR2 and CR123 Batteries

While both batteries are 3 volt batteries, the CR2 is 27 mm long with a diameter of 15.6 mm while the CR123 is 34.5 mm long with a diameter of 17mm. This makes the CR123 slightly larger than the CR2 and not interchangeable.

The CR123 also has a longer period of power output available to it. But let’s look at some of the detailed differences between these two batteries to understand them a bit better

The Differences and Which is Better

Before we dive into each battery let’s define some terms and some other battery rules.

First off, we are dealing with lithium batteries.This means we should not mix them with zinc batteries. If you have a mix of batteries, keep like with like and don’t put different power cells into the same device.

Second, batteries tend to use mAh or milliampere hours to denote just how long the battery can work or stay charged. This usually applies to when it is being actively used and the charge of each battery can be lengthened by not constantly using them.

Third, these particular lithium batteries tend to lose about 5% of their charge per month. This means even if they are not being used they are losing charge. Keep this in mind to help you plan when you need to swap out old batteries for fresh ones.

CR2

The CR2 battery is a small battery, roughly half the length of a standard AA. It is usually used in photographic equipment or cameras. However its small profile allows it to be placed in smaller equipment easily.

The overall length of the battery is 27 mm and its diameter is 15.6 mm. Due to its low discharge, this battery will outlast other options in terms of charge. Although the CR123 will have a longer charge life.

The CR2 typically has 750 mAh in its 3 volt charge when it is not rechargeable. Rechargeable options exist but some have smaller mAh ratings of 600 mAh all the way up to 800 mAh. Other versions even have as low as 400 and will have a shorter run time.

Most CR2 batteries will power a device for roughly 5.5 to 8 hours on their standard charge. After this they will need to be replaced. In the case of rechargeable batteries this is simplified to recharging.

CR123

The larger of the two options, the CR123 is significantly more powerful than the CR2. Coming in at 35.4 mm long with a diameter of 17 mm, the CR123 is roughly ¾ the size of a standard AA cell’s length but is slightly wider.

Despite the relative size of the CR123 to the CR2, the CR123 has a significantly different power output and charge life than the CR2.

Depending on the brand, the CR123 has twice the capacity of the CR2. In actual measurements the CR123 has a mAh rating of 1500 to 2500 mAh in non-rechargeable batteries. This significant increase of mAh equates to 6 to 60 hours of power.

This jump tends to sway people to use CR123s when they need longer charges and greater reliability from their equipment. For example weapon mounted flashlights or carried flashlights.

While rechargeable CR123s exist their mAh output generally drops to 700 mAh. While this is well within the range of most CR2 batteries, rechargeable CR123s fill a niche created by heavy usage.

If you do not want to be continually paying for CR123s, rechargeable versions allow you to keep your equipment running with emergency batteries on standby.

Name	Volts	mAh	Length	Diameter
CR2	3	750, non-rechargeable600/800 rechargeable	27 mm	15.6 mm
CR123	3	1500-2500, non-rechargeable700, rechargeable	34.5 mm	17 mm

Which Is Better?

The CR123 is clearly the more powerful battery. However, which one is better always comes down to what you are doing.

Obviously if your equipment requires a certain type of battery you will have to use that battery. If it needs a CR2 battery no amount of wishing will change it to accept a CR123 since they are not interchangeable.

CR123 is better for long term usage and reliability. However the CR2 will fit into smaller tools and take up less space. If you are trying to conserve space with your battery storage you have to consider what you need out of your equipment.

The CR2 is going to require more frequent changing and would need more spare batteries on hand. This is not as much of a problem when they are rather small, but batteries can be expensive. Having rechargeables on hand are still limited by the CR2’s charge output.

The CR123s have a longer run time and better energy use than the CR2. This is usually about 60% more power on average. This also transfers to the use of the battery itself.

CR123s will provide more power during use than a CR2 will. This means brighter light if you use it in a flashlight, etc. But this doesn’t matter if the device uses smaller batteries.

Conclusion

Batteries are a plug and play type of expendable. As long as you know the size of battery your device needs you will get the right type you need each time. Where the problem comes in is what type of equipment you need or want to use.

Carefully weighing the power output, the device’s footprint and storage, and the storage or type of battery you will need to use will impact what you decide to use. It doesn’t necessarily come down to a question of how much power it puts out but why you need that power and what the demands of your device are.

CR123s significantly outperform the CR2. But not every device is designed to accept CR123s. These two 3 volt batteries are nearly the same size but their performance and roles are very different.

Don’t try to make a CR2 do the job of a CR123 or vice versa.