Battery
Using 18650 Holder Battery with Arduino Uno
What is the 18650 Holder?
A basic single-cell 18650 battery holder, the standard building block for portable and battery-powered maker projects. It's simply a molded plastic clip with spring-loaded metal contacts sized for the common 18650 cylindrical Li-ion cell, giving a solderable or wire-lead connection point without needing to solder directly onto the battery itself — which is important, since soldering onto an 18650's bare terminals can damage the cell and is generally discouraged.
Specifications
| Cell compatibility | Single 18650 Li-ion cell (18mm diameter x 65mm length) |
| Contact type | Spring-loaded positive and negative metal contacts, no direct soldering to the cell required |
| Output | Raw, unregulated battery voltage — typically 3.0V-4.2V depending on charge state |
| Connection | Bare wire leads (usually red/black) or PCB-mount pins, depending on holder style |
| Mounting | Surface-mount screw holes or PCB-through-hole pins, model-dependent |
| Protection | None built in — holder is purely mechanical; use a protected 18650 cell or add a separate protection/charge circuit (e.g. TP4056) for safe charging and discharge cutoff |
18650 Holder Pinout
| Pin | Name | Description |
|---|---|---|
| 1 | + (Positive lead) | Connects to the cell's positive terminal via the spring contact |
| 2 | - (Negative lead) | Connects to the cell's negative terminal via the spring contact |
The holder itself provides no charge control or over-discharge protection — pair it with a charge/protection module like the TP4056 (with built-in DW01 protection) if the project charges the cell in place, and always observe correct polarity since 18650 cells can vent or be damaged if reverse-connected.
Setting Up 18650 Holder with Arduino Uno
Wiring
| Component pin | Arduino Uno pin | Note |
|---|---|---|
| + (Positive lead) | R1 (100k) to A0, R1 also to + | Divider midpoint feeds A0 — keeps max voltage under 5V |
| + (Positive lead) | R2 (100k) from A0 to GND | Second half of the divider — halves the battery voltage before it reaches A0 |
| - (Negative lead) | GND | Common ground |
Example code
A single 18650 cell is 3.0-4.2V, well under the Uno's 5V ADC reference, so a simple 1:1 (equal-value resistor) divider is enough headroom. Do not feed the raw cell voltage into VIN to power the Uno directly — 3.7V nominal is below the onboard regulator's minimum input.
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