16340 vs CR123A
The 16340 is a 3.6 V rechargeable lithium-ion cell in the CR123A's footprint. The CR123A is a 3 V single-use lithium cell.
The 16340 is the rechargeable version of the CR123A, and it is often sold as RCR123A. It fits the same slot, but it runs at 3.6 volts against the CR123A's 3, and a freshly charged one is nearer 4.2. Some torches and cameras are built to accept either and say so. Many are not, and feeding one 4.2 volts can damage it. Check your manual before swapping — and never put a CR123A in a charger.
- Verdict:
- Same slot, different voltage — check the device is rated for both
- Interchangeable:
- no
These fit the same space but are not electrically compatible
The 16340 runs at 3.6 V against the CR123A’s 3 V — a 0.6 V difference between two cells that drop into the same compartment. Nothing about the fit stops you making this mistake, so check the code on the cell, not its shape. The CR123A is also single-use: putting one in a charger built for the 16340 can make it vent, leak or catch fire.
Side-by-side specifications
| Specification | 16340 | CR123A |
|---|---|---|
| Chemistry | Li-ion | Lithium |
| Type | Cylindrical | Cylindrical |
| Nominal voltage | 3.6 V | 3 V |
| Diameter | 16 mm | 17 mm |
| Height | 34 mm | 34.5 mm |
| Typical capacity | 650–800 mAh | 1400–1600 mAh |
| Rechargeable | Yes | No |
| Also sold as | RCR123A, ICR16340, IMR16340 | CR17345, DL123A, EL123A, 123 |
Size comparison
Near enough to interchange by hand — 16 × 34 mm against 17 × 34.5 mm — which is precisely why the voltage difference matters here.
Rechargeable against single-use
The 16340 is lithium-ion and designed to be recharged. The CR123A is a primary lithium cell and must never go in a charger — doing so can make it vent or burst.
Voltage
3.6 V nominal for the 16340 against 3 V for the CR123A, and up to 4.2 V straight off the charger. Devices rated for both usually print it; treat silence as a no.
Runtime
650–800 mAh against 1400–1600 mAh. The single-use CR123A holds roughly twice as much per cell, which is why it stays the choice for smoke alarms and equipment left alone for years.
Can I use a CR123A instead of a 16340?
No — and the fit will not stop you. The CR123A measures 17 × 34.5 mm against 16 × 34 mm, close enough that it will sit in the same compartment. The problem is electrical: 3.6 V against 3 V. Fitting the 16340 where the CR123A belongs feeds a device more than it was built for, which can damage it immediately or shorten its life. Match the code printed on the cell you removed.
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.