Overview
The LilyPad CR2032 Coin Cell Battery Holder is a small purple PCB designed for wearable and e-textile projects. It accepts a standard 3V CR2032 coin cell, has a built-in slide on/off switch, and exposes large solder/sew pads for + and − that you can either solder wires to or stitch through with conductive thread.
The "LilyPad" form factor was created by Sparkfun for projects that integrate electronics into clothing — light-up jackets, smart sweatshirts, costume props, badge electronics, and any wearable that needs a tiny, flat, low-profile power source. The 3V output runs LilyPad-class boards (LilyPad Arduino, LilyTwinkle, LilyMini), most LEDs, and any low-power 3V sensor.
Each holder takes a single CR2032 — that's 220-240 mAh of energy at 3V, enough to power a slow-blinking LED for many days or a low-duty-cycle BLE sensor for months. This is a 3-pack so you can build three projects at once or have spares for the inevitable battery swap.
At a Glance
Specifications
| Parameter | Value |
| Compatible Battery | CR2032 coin cell (3V lithium) |
| Nominal Voltage | 3.0V (fully charged: 3.3V, depleted: 2.0V) |
| Capacity | 220 - 240 mAh (battery dependent) |
| Maximum Continuous Current | ~10 mA (longer life at lower draw) |
| Pulse Current | Up to 50 mA briefly |
| Switch Type | SPST slide switch (ON / OFF) |
| Solder/Sew Pads | 4 large pads (+ and − marked) |
| Form Factor | Round LilyPad (purple PCB) |
| Diameter | ~22 mm |
| Thickness | ~5 mm with battery installed |
| Pack Quantity | 3 holders per pack |
Pinout Diagram
Wiring Guide
Solder Wiring (Standard Projects)
For breadboard and standard PCB projects, solder wires through the + and − pads. Make sure the slide switch is OFF before soldering, and let the iron tip cool against the pad rather than touching the battery.
| Holder Pad | Connect To |
|---|---|
| + | VCC of your circuit (3V rail) |
| − | GND of your circuit |
Sewable Circuit (E-Textile Projects)
For wearables, the holder is designed to be sewn directly into fabric using conductive thread. Each pad has multiple stitch holes for a strong, low-resistance connection.
| Step | Action |
|---|---|
| 1 | Position the holder where you want it on the garment. |
| 2 | Tack the holder in place with regular thread first (just to hold it). |
| 3 | Use conductive thread to stitch through the + pad to your LED's + leg. |
| 4 | Use a separate piece of conductive thread for the − pad → LED's − leg. |
| 5 | Knot and seal each end with clear nail polish to prevent fraying. |
Direct LED (No Microcontroller)
The simplest project: power an LED directly from the holder. The CR2032's internal resistance limits current naturally, but for predictable behavior add a 100Ω current-limit resistor in series.
| Component | Connection |
|---|---|
| + pad | LED anode (long leg) through 100Ω resistor |
| LED cathode (short leg) | − pad |
| Slide switch | Position to ON to light the LED |
Code Examples
The CR2032 holder is a passive power source — no microcontroller code is needed. The slide switch handles on/off, and the wired connections do the rest. Below is a typical Arduino LilyPad sketch that runs from this holder.
LilyPad Arduino — Slow Blink (Long Battery Life)
// LilyPad Arduino - Slow blink for long battery life from CR2032
// Wire the holder + to LilyPad + (VCC), holder - to LilyPad -.
// Wire an LED with 100 ohm resistor between any GPIO and -.
const int ledPin = 5;
void setup() {
pinMode(ledPin, OUTPUT);
}
void loop() {
digitalWrite(ledPin, HIGH);
delay(50); // brief flash
digitalWrite(ledPin, LOW);
delay(2000); // long off — saves battery
}
Estimating Battery Life
CR2032 capacity: ~225 mAh
Always-on LED at 10 mA: 225 / 10 = 22.5 hours
Always-on LED at 1 mA: 225 / 1 = 225 hours (~9 days)
50 ms flash every 2 s, 10 mA average draw = 0.25 mA:
225 / 0.25 = 900 hours (~37 days)
Deep-sleep MCU + occasional BLE ad, 50 µA average:
225 / 0.05 = 4500 hours (~6 months)