Coin cell batteries — also called button batteries — are the small, disc-shaped batteries that power everything from car key fobs to wristwatches to the clock on your computer motherboard. They’re ubiquitous, inexpensive, and often ignored until the device they power suddenly stops working. This guide explains the different types, how to read the confusing numbering system, and how to replace them safely.
What Are Coin Cell Batteries?
Coin cell batteries are small, cylindrical batteries with a diameter much greater than their thickness — hence the “coin” shape. They come in a range of chemistries and sizes, each suited to different applications and power requirements.
The Numbering System Explained
Coin cell battery numbers follow a consistent pattern that encodes the chemistry and size:
- First letter(s): Chemistry code
- CR = Lithium (most common, 3V)
- LR = Alkaline (1.5V)
- SR = Silver oxide (1.55V, very stable voltage)
- BR = Lithium carbon monofluoride (wide temperature range)
- ZA / PR = Zinc-air (for hearing aids, activated by removing a tab)
- Numbers: Size code. For most types, the first two digits are the diameter in mm, the last two are the height in tenths of mm.
- CR2032: 20mm diameter, 3.2mm thick
- CR2025: 20mm diameter, 2.5mm thick
- CR2016: 20mm diameter, 1.6mm thick
- CR1632: 16mm diameter, 3.2mm thick
Most Common Coin Cell Types and Their Uses
| Battery | Chemistry | Voltage | Common Uses |
|---|---|---|---|
| CR2032 | Lithium | 3V | Car key fobs, computer CMOS, fitness trackers, medical devices, small remotes |
| CR2025 | Lithium | 3V | Key fobs, calculators, some watches |
| CR2016 | Lithium | 3V | Thin key fobs, some calculators, laser pointers |
| CR1632 | Lithium | 3V | Smaller key fobs, some remotes |
| CR1220 | Lithium | 3V | Small electronics, glucose meters |
| LR44 / AG13 | Alkaline | 1.5V | Toys, small remotes, calculators, laser pointers |
| SR626SW / AG4 | Silver oxide | 1.55V | Watches (accurate voltage important for quartz movement) |
| SR44 / 357 | Silver oxide | 1.55V | Camera light meters, precision instruments, watches |
| ZA13 / PR48 | Zinc-air | 1.4V | Hearing aids (size 13 — orange tab) |
| ZA312 / PR41 | Zinc-air | 1.4V | Hearing aids (size 312 — brown tab) |
How to Replace a Coin Cell Battery
- Identify the battery type. Check the device manual, the existing battery itself, or look up the device model online. The battery number is printed on the face of the cell.
- Open the battery compartment. Most coin cell compartments have a small slot for a coin or flat screwdriver. Turn the cover to the unlock symbol and slide or pop it out. Car key fobs typically have a seam you pry open with a flat screwdriver at the marked point.
- Note the orientation. Before removing the old battery, note which side faces up (usually the positive/+ side faces up or is marked). Take a photo if you’re unsure.
- Remove the old battery. A plastic pry tool or a toothpick works well for popping the old cell out without touching the contacts with metal tools.
- Install the new battery. Match the orientation. The positive (+) side is usually marked. Press in until it seats — you’ll often feel a slight click.
- Test the device. If it doesn’t work immediately, try pressing a button or reinitializing — some devices (car key fobs, glucose meters) need a brief reset after battery replacement.
Best Brands for Coin Cell Batteries
- Panasonic: Consistently top-rated for CR2032 and other lithium coin cells. Excellent shelf life (10 years) and capacity.
- Energizer: Good quality, widely available, standard choice for most applications.
- Renata (now Swatch Group): Premium watch batteries. The standard choice for Swiss watch movements.
- Maxell: Good quality for general use.
- Avoid: No-brand batteries from unknown sources — coin cells are frequently counterfeited, and a cheap CR2032 from an unlabeled bulk pack may have a fraction of the rated capacity.
Shelf Life and Storage
Lithium coin cells (CR series) have a shelf life of 10 years when stored in their original packaging at room temperature. Alkaline (LR series) last 5–7 years. Silver oxide (SR series) last 3–5 years. Store at room temperature away from humidity. Do not store loose in a drawer where they can contact other metal objects and short-circuit — keep them in their packaging until use.
Frequently Asked Questions
Can I use a CR2025 instead of CR2032?
They are the same diameter (20mm) but different thickness (2.5mm vs 3.2mm). A CR2025 will physically fit in a CR2032 slot in most devices and will work, but has about 20% less capacity so it will run out faster. CR2016 (1.6mm) will also fit physically but has even less capacity. Use the specified battery when possible.
Why do watch batteries use silver oxide instead of lithium?
Silver oxide batteries have an extremely flat discharge curve — they hold almost exactly 1.55V throughout their life, only dropping sharply at the very end. Quartz watch movements are sensitive to voltage variation, and the stable silver oxide voltage ensures accurate timekeeping throughout the battery’s life. Lithium or alkaline batteries have a more gradual voltage decline that can affect timing accuracy.
How do I know when a coin cell needs replacing?
The device will typically give you clear signals: a key fob with reduced range, a watch losing time, a computer CMOS error message at boot (‘CMOS battery failure’ or ‘Date/Time not set’), or a device that simply stops responding. Some devices have battery level indicators. Most lithium coin cells give very little warning before failure — they maintain good voltage until near the end, then drop off quickly.
Are there rechargeable coin cell batteries?
Yes — rechargeable coin cells exist (LIR2032, LIR2025, etc.) but they output 3.6V instead of 3V and should only be used in devices specifically designed for rechargeable coin cells. Using a 3.6V rechargeable in a device designed for a 3V lithium primary cell can damage the device.
