CR123A vs 18650

A single 3.6 V rechargeable 18650 against 3 V single-use CR123A cells. Two CR123A approximate one 18650 in length, which is why many torches accept either.

Quick answer

These are different cells, but a lot of torches accept both, and there is a reason. Two CR123A cells stacked end to end come out close to the length of a single 18650, and their diameters are within a millimetre. So a tube cut for one 18650 often takes two CR123A instead. The catch is voltage: two CR123A in series give 6 volts against the 18650's 3.6, so this only works where the manufacturer says it does. Check the manual, not the tape measure.

Verdict:: Many torches take either — two CR123A stack to an 18650's length
Interchangeable:: no

Side-by-side specifications

CR123A compared with 18650
Specification	CR123A	18650
Chemistry	Lithium	Li-ion
Type	Cylindrical	Cylindrical
Nominal voltage	3 V	3.6 V
Diameter	17 mm	18 mm
Height	34.5 mm	65 mm
Typical capacity	1400–1600 mAh	2000–3500 mAh
Rechargeable	No	Yes
Also sold as	CR17345, DL123A, EL123A, 123	INR18650, ICR18650, NCR18650

Size comparison

CR123A

Ø 17 mm · H 34.5 mm

18650

Ø 18 mm · H 65 mm

These cells do not share a footprint, so one will not sit correctly in the other's compartment.

Why the tube fits both

A CR123A is 17 × 34.5 mm. Two end to end run about 69 mm against the 18650's 65 mm, at 17 mm across against 18 mm. Torch designers exploit that deliberately.

The voltage is not the same

Two CR123A in series deliver 6 V; one 18650 delivers 3.6 V. Only a driver designed for that range handles both, which is why the option has to be stated by the manufacturer.

Rechargeable against single-use

The 18650 recharges. The CR123A does not and must never go in a charger. For a torch used often the 18650 is cheaper to run; for one kept in a drawer for emergencies, the CR123A's shelf life wins.

Can I use a 18650 instead of a CR123A?

Not directly. The 18650 measures 18 × 65 mm against 17 × 34.5 mm for the CR123A, so it will not seat properly in the same compartment.

CR123A specs →18650 specs →

Check before you swap. Batteries with similar dimensions are not always interchangeable. Always verify voltage, chemistry and the requirements printed in your device manual before fitting a replacement.

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