What is equivalent to a INR21700?

2170, INR21700, NCR21700, 21700 Li-ion — all the same 3.6 V cell under different manufacturer codes.

Can I use a 18650 instead of a INR21700?

Three millimetres wider and five longer, holding around half again the charge. A 21700 will not enter an 18650 tube; an 18650 in a 21700 tube rattles and may arc.

Is the INR21700 rechargeable?

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

INR21700 battery

What replaces a INR21700

2170, INR21700, NCR21700, 21700 Li-ion

3.6 V lithium-ion (rechargeable), 21 × 70 mm (diameter × height)

The INR21700 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: INR21700
Nominal voltage: 3.6 V
Chemistry: Lithium-ion (rechargeable)
Size: 21 × 70 mm (diameter × height)
Typical capacity: 4800 mAh
Rechargeable: Yes

Codes that mean the same battery

Different manufacturers, one physical battery. Voltage, chemistry and dimensions all match.
Code	Fits?
2170	Yes — same cell
INR21700	Yes — same cell
NCR21700	Yes — same cell
21700 Li-ion	Yes — same cell

Codes that look close but are not

Code	Why it is not a substitute
18650	Three millimetres wider and five longer, holding around half again the charge. A 21700 will not enter an 18650 tube; an 18650 in a 21700 tube rattles and may arc.

Where it turns up

Tesla Model 3 and Model Y packs
Modern high-output torches
E-bike and scooter batteries
Newer cordless tool packs

Genuine capacity runs 4000–5000 mAh. The name is the size: 21 mm across, 70.0 mm long.

Common questions

What is equivalent to a INR21700?: 2170, INR21700, NCR21700, 21700 Li-ion — all the same 3.6 V cell under different manufacturer codes.
Can I use a 18650 instead of a INR21700?: Three millimetres wider and five longer, holding around half again the charge. A 21700 will not enter an 18650 tube; an 18650 in a 21700 tube rattles and may arc.
Is the INR21700 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
ICR18650 battery 3.6 V lithium-ion (rechargeable)
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)
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