Lithium Coin Battery Guide: Codes, Types, Safety and How to Choose
A lithium coin battery is a flat, round, non-rechargeable cell that gives a steady 3 volts and keeps its charge for years on the shelf. It powers key fobs, watches, car remotes, computer motherboards, thermometers and many small gadgets. The ones in key fobs are almost always CR-type cells such as the CR2032 and CR2025. This guide explains how coin batteries work, how to read the codes, how to choose the right one, and how to handle them safely.
Quick answer
For a key fob, buy a lithium “CR” coin cell with the exact code your fob uses (usually CR2032 or CR2025). Do not use rechargeable LIR cells or 1.5-volt button cells. Store spares in their original packs and keep every coin battery out of reach of children.
What is a lithium coin battery?
It is a small, round, primary (non-rechargeable) cell, usually made with a lithium metal negative electrode and a manganese dioxide positive electrode. Its steel case is the battery, and the two flat faces are the terminals. The printed face is positive (+) and the plain face is negative (−). Because lithium chemistry gives 3 V instead of the 1.5 V of an alkaline cell, a coin battery packs a lot of power into a thin disc.
How to read a coin battery code
- CR: lithium manganese dioxide chemistry, round shape.
- First two digits: the diameter in millimetres. In CR2032, “20” means 20 mm.
- Last two digits: the thickness in tenths of a millimetre. “32” means 3.2 mm.
So a CR2032 is 20 mm wide and 3.2 mm thick, and a CR2025 is 20 mm wide and 2.5 mm thick. See the full key fob battery size chart for other sizes.
Common coin battery families
| Prefix | Type | Voltage | Notes |
|---|---|---|---|
| CR | Lithium manganese dioxide, non-rechargeable | 3 V | The standard for key fobs |
| BR | Lithium carbon monofluoride, non-rechargeable | 3 V | Suited to low-drain, wide-temperature uses |
| LIR | Lithium-ion, rechargeable | about 3.6 V | Same shape as CR but not a drop-in replacement |
| LR / AG | Alkaline button cell | 1.5 V | Different voltage; not for key fobs that need a 3 V cell |
| SR | Silver oxide button cell | 1.55 V | Common in watches |
The CR2032 and LIR2032 look almost identical, but the LIR runs at a higher voltage and is built for rechargeable devices. Do not put it in a key fob unless the fob maker says so.
CR2032 and CR2025 specifications
| Spec | CR2032 | CR2025 |
|---|---|---|
| Voltage | 3.0 V | 3.0 V |
| Diameter | 20 mm | 20 mm |
| Height | about 3.2 mm | about 2.5 mm |
| Capacity | about 235 mAh | about 170 mAh |
The figures come from the Energizer datasheets for the CR2032 and CR2025. For the choice between them, see CR2032 vs CR2025.
Why key fobs use lithium coin cells
- Steady voltage. The fob’s radio and chip work best at a stable 3 V.
- Long shelf life. A spare in a drawer still works after years.
- Thin and light. A coin cell fits in a slim key.
- Good in temperature swings. Lithium chemistry copes better with cold than many alternatives.
- Low self-discharge. The cell loses very little when idle.
How long does a lithium coin battery last?
On the shelf, lithium coin cells keep their charge for years. In a key fob, a cell commonly lasts one to a few years, depending on how often you press the buttons, whether it is a smart key, and the temperature. See how long key fob batteries last for details.
How to choose a good coin battery
- Match the code on your old battery.
- Choose a recognised brand. We compare several in best CR2032 batteries for key fobs.
- Check the expiry date on the pack.
- Buy from a trusted seller to avoid fake or very old stock.
- Look for child-resistant packaging.
You can browse lithium coin batteries on Amazon. As an Amazon Associate, ReplaceKeyFob earns from qualifying purchases; see our disclaimer.
How to install a coin battery in a key fob
- Open the fob. See how to open a key fob.
- Photograph the old battery and note the direction. See the polarity guide.
- Lift the old cell out with a plastic tool.
- Insert the new cell by its edges, the same way up.
- Close the case and test the buttons.
If you want to do it yourself with confidence, read can I replace a key fob battery myself?
Safety: the most important part
Coin batteries are small enough for a child to swallow, and that is dangerous. When a lithium coin cell lodges in the throat or gullet, the moisture in saliva can trigger an electrical reaction that causes serious tissue damage within hours. To keep children and pets safe:
- Keep spare and used coin batteries out of sight and out of reach.
- Make sure the battery compartment of any device is secure.
- Close key fobs properly, so children cannot open them.
- Do not leave the old battery on a table after you replace it.
- Tape both faces with clear tape before disposal.
In the United States, federal rules that followed Reese’s Law require child-resistant packaging and warnings on coin and button batteries and on products that use them.
If you think a child swallowed a battery
Go to the emergency room immediately. Do not wait for symptoms, and do not induce vomiting. Call the National Battery Ingestion Hotline at 1-800-498-8666, or Poison Help at 1-800-222-1222. More guidance: Poison Control.
Other safety rules
- Never try to recharge a CR cell. They are not designed for it and can leak or overheat.
- Do not heat or burn batteries.
- Do not short-circuit them. Keep loose cells away from coins and keys.
- Do not mix old and new cells, or different brands, in devices that use more than one.
- Do not use a leaking or swollen cell. Wear gloves, wipe the contacts and replace it.
Storage
Keep coin cells in their original packaging, at room temperature, away from direct sun and heat, and away from metal objects. Do not store them in the car. Use the oldest first.
Disposal and recycling
Used coin cells still hold some charge, so they should not go loose into household waste. Cover both faces with clear tape and take them to a battery recycling point. Many electronics shops and local recycling centres collect them. Check your local rules, since they differ by area.
Coin cell, button cell or watch battery?
These names overlap. “Button cell” is a general term for small round batteries, which can be lithium, alkaline or silver oxide. “Coin cell” usually refers to the larger flat lithium cells such as the CR2032, which look like a coin. “Watch battery” is a loose name for the smallest ones, which are often silver oxide. When you shop, ignore the nickname and go by the code on the battery, because the chemistry and voltage depend on it.
Devices that use a CR2032 or CR2025
- Car key fobs and keyless-entry remotes.
- Computer motherboards, which use one to keep time when the machine is off.
- Bathroom scales, thermometers, and small medical monitors.
- Fitness trackers and some watches.
- Garage-door openers, small remote controls and key finders.
- Toys, cards and novelty items with lights or sounds.
The same battery may be used in many of these, so a spare is useful around the house. Remember that any device with a coin cell is a risk for small children, not just the key fob.
Common mistakes
- Assuming that any 20 mm coin cell will do. Thickness and chemistry matter.
- Buying a rechargeable LIR cell by mistake.
- Throwing used cells into a bin loose, or leaving them on a counter.
- Carrying loose spares in a pocket or purse with coins and keys.
- Choosing the cheapest unbranded cell for a device you rely on.
Environmental note
Lithium coin cells are small, but they still contain metals worth recovering, and they should not end up in landfill if you can avoid it. Recycling programmes and retailer drop-off points accept them in many places. Buying a branded cell that lasts longer, and replacing the battery only when you need to, reduces waste.
Troubleshooting a coin battery that “does not work”
- Check the direction.
- Check the code and size.
- Wipe the contacts with a dry cloth.
- Try a second battery from a different pack.
- Test the voltage: a fresh CR cell reads about 3 V or a bit higher.
If a fresh battery still does not help, see what to do when a battery replacement did not fix the problem and whether the fob needs reprogramming.
Frequently asked questions
What is a lithium coin battery?
A small round non-rechargeable lithium cell, usually 3 volts, used in key fobs, watches and many small devices.
What does CR2032 mean?
CR means lithium, round. 20 is the diameter in millimetres, and 32 is the thickness in tenths of a millimetre: 3.2 mm.
Can I recharge a CR2032?
No. Only LIR cells are rechargeable, and they run at a different voltage.
Are lithium coin batteries dangerous?
They are safe when used properly, but a swallowed one is an emergency. Keep them away from children.
How should I dispose of a coin battery?
Tape both faces and take it to a battery recycling point.
Which coin battery do I need for my key fob?
Match the code on the old battery or in the manual. Most fobs use a CR2032 or CR2025.
Can I use an alkaline button cell instead?
No. Alkaline button cells are 1.5 V, and a fob designed for 3 V will not work properly.
Bottom line
A lithium coin battery is a simple, reliable power source, as long as you use the right code and handle it safely. For key fobs, choose a fresh CR cell from a known brand, keep a spare, and always keep coin batteries out of children’s reach.