What is equivalent to a ICR18650?

INR18650, IMR18650, NCR18650, 1865, 18650 Li-ion — all the same 3.6 V cell under different manufacturer codes.

Can I use a Protected 18650 instead of a ICR18650?

A protection board on the negative end adds 2–5 mm, making the cell 67–70 mm long. Torches and packs built for unprotected cells will not close on one, and battery-bay springs built for protected cells may not reach an unprotected one.

Is the ICR18650 rechargeable?

Yes. Use a charger made for its chemistry and never substitute a primary cell of the same size.

ICR18650 battery

What replaces a ICR18650

INR18650, IMR18650, NCR18650, 1865, 18650 Li-ion

3.6 V lithium-ion (rechargeable), 18 × 65 mm (diameter × height)

The ICR18650 is a rechargeable 3.6 V lithium-ion (rechargeable) cylindrical. The codes below are the same physical cell sold under different manufacturer names, and any of them will fit.

Specification

IEC designation: ICR18650
Nominal voltage: 3.6 V
Chemistry: Lithium-ion (rechargeable)
Size: 18 × 65 mm (diameter × height)
Typical capacity: 3000 mAh
Rechargeable: Yes

Codes that mean the same battery

Different manufacturers, one physical battery. Voltage, chemistry and dimensions all match.
Code	Fits?
INR18650	Yes — same cell
IMR18650	Yes — same cell
NCR18650	Yes — same cell
1865	Yes — same cell
18650 Li-ion	Yes — same cell

Codes that look close but are not

Code	Why it is not a substitute
Protected 18650	A protection board on the negative end adds 2–5 mm, making the cell 67–70 mm long. Torches and packs built for unprotected cells will not close on one, and battery-bay springs built for protected cells may not reach an unprotected one.
Button-top vs flat-top	A flat-top cell will not make contact in a series holder designed for button tops. Same cell electrically, and a very common reason a new battery appears dead.
Two CR123A	Two 3 V primaries stack to roughly the same length and 6 V. Some torches accept either and say so on the body; assuming without checking has destroyed a lot of drivers.

Where it turns up

Laptop battery packs and power banks
High-output torches and headlamps
Cordless power tools
Tesla Model S and early EV packs

Capacity runs 2000–3600 mAh for genuine cells; anything claiming 6000 mAh or more on a wrapper is a relabelled cell and usually holds under 1000. Nominal 3.6–3.7 V depending on cathode, 4.2 V fully charged, and 2.5–3.0 V is the floor below which the cell is damaged.

Common questions

What is equivalent to a ICR18650?: INR18650, IMR18650, NCR18650, 1865, 18650 Li-ion — all the same 3.6 V cell under different manufacturer codes.
Can I use a Protected 18650 instead of a ICR18650?: A protection board on the negative end adds 2–5 mm, making the cell 67–70 mm long. Torches and packs built for unprotected cells will not close on one, and battery-bay springs built for protected cells may not reach an unprotected one.
Is the ICR18650 rechargeable?: Yes. Use a charger made for its chemistry and never substitute a primary cell of the same size.

LR6 battery 1.5 V alkaline
LR03 battery 1.5 V alkaline
LR20 battery 1.5 V alkaline
HR6 battery 1.2 V nickel-metal hydride
LR14 battery 1.5 V alkaline
CR17345 battery 3 V lithium (primary)
HR03 battery 1.2 V nickel-metal hydride
8LR932 battery 12 V alkaline
FR6 battery 1.5 V lithium (primary)
INR21700 battery 3.6 V lithium-ion (rechargeable)
4LR44 battery 6 V alkaline
CR15H270 battery 3 V lithium (primary)

Sources

Typical range compiled from manufacturer specifications — At One Place

How these figures are compiled and checked