18650 lithium-ion cell pinout

18650 identifies a cylindrical form factor. The Molicel INR-18650-P28A is one example, with a 3.6 V nominal voltage and 2.8 Ah typical capacity.

Bare cylindrical cell

2 contacts Current package

Protected pack connector 2 contacts

Molicel and Honcell · Molicel INR-18650-P28A · 18.6 mm maximum diameter × 65.2 mm maximum height.

Bare cylindrical cell pinout

Bare cylindrical cell

Side view with the insulated positive cap to the left. The map uses 1 and 2 as terminal identifiers.

Selected pin details

2 · −

Negative terminal · Ground

The flat bottom is negative. Keep the steel can and positive cap insulated from one another.

Molicel P28A datasheet, p. 1

Electrical limits · Link to this pin

All 2 pins

Pin	Signal	Direction	Function
1	+ Positive terminal	Positive terminal	The positive cap sits at the end with the insulating ring. The ring separates it from the surrounding can.
2	− Negative terminal	Negative terminal	The flat bottom is negative. Keep the steel can and positive cap insulated from one another.

Signal assignments

Cell polarity

The positive cap and negative bottom are opposite ends of the cylinder. A metal object touching both polarities can short the cell. Use a factory-assembled protected pack for the wiring examples.

Electrical limits

Parameter	Limit	Conditions and source
Nominal voltage3.6 V	3.6 V	Cell model INR-18650-P28A. Molicel P28A datasheet, p. 1
Capacity2.8 Ah typical · 2.7 Ah minimum	2.8 Ah typical · 2.7 Ah minimum	Cell figures. Refer to the manufacturer’s curves for current and temperature effects. Molicel P28A datasheet, p. 1
Characterized voltage endpoints4.2 V charge · 2.5 V discharge	4.2 V charge · 2.5 V discharge	Cell manufacturer’s values. Pack thresholds and equipment operating limits depend on the protected assembly. Molicel P28A datasheet, p. 1
Maximum cell dimensionsØ 18.6 mm × 65.2 mm	Ø 18.6 mm × 65.2 mm	The protected pack uses a different mechanical envelope. Molicel P28A datasheet, p. 1

Models and documents

This reference covers the bare Molicel INR-18650-P28A and the separately documented Honcell HCC18650FC protected assembly. Check the exact manufacturer code for chemistry, voltage, capacity, load rating, protection and fit.

INR-18650-P28A: Industrial bare cell described in the Molicel product datasheet.

Molicel INR-18650-P28A datasheet· Cell dimensions, ratings and polarity drawing.
Honcell HCC18650FC protected pack datasheet· ED-RE-02 · Electrical ratings, connector drawing and pack protection, pp. 4–7.
CPSC safety notice on loose 18650 cells· January 8, 2021 · Handling and short-circuit hazards.
Source register· Manufacturer URLs, applicability and file checksums.