18650 3.7V 2500mAh Li-Ion Rechargeable Cell

3.7V 2500mAh 18650 lithium-ion cell for battery packs, power banks and DIY projects.

₹90 + 18% GST

SKU: BOTBIT-PWR-10 · Best for: DIY and replacement power banks

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Overview

About 18650 3.7V 2500mAh Li-Ion Rechargeable Cell.

The 18650 is the workhorse rechargeable lithium-ion cell of the DIY world. This 3.7V nominal, 2500mAh cell delivers the energy density and cycle life that make 18650s the standard choice for power banks, battery packs, torches and portable electronics projects across India.

At 3.7V nominal (4.2V fully charged, ~2.5-3.0V empty) and 2500mAh capacity, a single cell stores roughly 9.25Wh. It uses the universal 18650 form factor - about 65mm long and 18mm in diameter - so it drops straight into standard holders, spot-welded packs and off-the-shelf 18650 chargers.

It is popular because it is affordable, rechargeable for hundreds of cycles, and easy to source. Combine several in series/parallel to build packs of almost any voltage and capacity.

Key features

Why it stands out.

3.7V nominal Li-ion chemistry with 4.2V full-charge voltage

2500mAh rated capacity (~9.25Wh energy)

Standard 18650 cylindrical form factor - fits common holders and chargers

Rechargeable for hundreds of charge/discharge cycles

Suitable for series/parallel packs to build higher voltage/capacity

Flat-top or button-top styles available for pack building

Specifications

Selection facts.

Chemistry	Lithium-ion (Li-ion)
Nominal voltage	3.7V
Full-charge voltage	4.2V
Cut-off (discharge) voltage	~2.5 - 3.0V
Rated capacity	2500mAh
Energy	~9.25Wh
Diameter	~18mm
Length	~65mm
Standard charge current	0.5C (~1.25A)
Recommended charger	TP4056 / dedicated 18650 charger

Applications

Where it is used.

DIY and replacement power banks
Custom battery packs for robots, e-bikes and RC (in series/parallel)
High-brightness LED torches and headlamps
Battery backup for ESP32/Arduino and IoT sensor nodes
Portable Bluetooth speakers and audio projects
Solar lighting and off-grid storage builds

Buying guide

How to choose.

Choose 18650 cells when you need rechargeable energy in a compact, standard package that fits holders and off-the-shelf chargers. A single 2500mAh cell suits low-drain projects; wire several in parallel for more runtime or in series for higher voltage.

Always charge with a proper Li-ion charger that cuts off at 4.2V - never a plain DC supply. The TP4056 module (BOTBIT-PWR-09) is the cheapest safe option for one cell. For packs, use a BMS matched to your S count.

Pair with an 18650 holder (BOTBIT-PWR-11) for solderless mounting, or spot-weld nickel strip for permanent packs. If your circuit needs 5V, add a boost converter after the cell.

FAQ

Common questions.

How do I charge this cell safely?

Use a dedicated Li-ion charger or a TP4056 module that charges at constant current then holds 4.2V. Never charge a lithium cell from a bare bench supply without a proper CC/CV cut-off.

Can I use this to power a 5V Arduino or ESP32 directly?

Not directly - it ranges 3.0-4.2V. Feed an ESP32/ESP8266 3.3V regulator from it, or add a boost converter to get a stable 5V for Arduino and USB devices.

How many cells do I need for a 12V pack?

Three cells in series (3S) give ~11.1V nominal and 12.6V fully charged. Add cells in parallel to increase capacity, and always use a matching BMS.

Is it flat-top or button-top?

Cells ship in the standard style listed for the SKU. Flat-tops suit spot-welded packs; button-tops seat better in some torches and holders. Check your holder before ordering for pack building.

Are these genuine 2500mAh cells?

The rated capacity is 2500mAh. Real-world usable capacity depends on discharge rate and temperature; expect slightly less at high current draw. Store partially charged and away from heat.