Button Battery Table
| Letter code | Chemistry | Nominal voltage | Everyday meaning |
|---|---|---|---|
| — | Zinc-carbon | 1.5 V | the original cheap cell, mostly historical |
| L | Alkaline | 1.5 V | LR44, A76, LR936 - the everyday remote and toy cell |
| S | Silver oxide | 1.55 V | SR44, SR936 - watches and instruments that need a flat discharge curve |
| P | Zinc-air | 1.4 V | hearing-aid cells (air activated, tab until use) |
| C | Lithium / manganese dioxide | 3 V | CR2032, CR2025, CR2016 - car keys, scales, motherboards |
| B | Lithium / carbon monofluoride | 3 V | long-shelf-life cameras and meters |
| E | Lithium / thionyl chloride | 3.6 V | industrial memory backup and meters |
| F | Lithium / iron disulfide | 1.5 V | 1.5 V lithium drop-ins for high-drain use |
| G | Copper oxide | 1.5 V | rare legacy cells |
| M / N | Mercury oxide (withdrawn) | 1.35 V | banned - toxic mercury; old instruments calibrated for it |
A coin cell's code is a spec sheet compressed to five characters, and the first letter does all the chemistry: L is alkaline, S is silver oxide, P is zinc-air, C is lithium manganese dioxide. The numbers are pure geometry - in CR2032, the CR is lithium round, 20 is the diameter in millimeters, and 32 is the height in tenths of a millimeter. Once the scheme clicks, a drawer full of unlabeled codes reads itself, and the chart is the key.
The voltage column is where the real decisions live: the 1.5-volt family (alkaline, silver, zinc-air) and the 3-volt lithium family are not interchangeable even where the coin fits, because devices are engineered around the discharge curve, not just the number. That is also the LR44-versus-SR44 trap - the same physical size, but alkaline sags under load while silver oxide holds a flat curve, so the precision instrument calibrated for SR drifts on the cheap LR. The chart also keeps one row the industry would rather forget: mercury cells, withdrawn for toxicity, still specified in old instruments.
How to use
- Decode before you buy: read the letter for chemistry (L alkaline, S silver, C lithium), the first pair of digits for diameter in millimeters, and the last pair for height in tenths - so CR2025 is a 3-volt lithium coin 20 mm across and 2.5 mm thick, a hair slimmer than CR2032 and a common bad fit in fobs that need the spring pressure.
- Match chemistry to the job: remotes and toys take L alkaline without complaint, watches and light meters want S silver oxide for the flat voltage curve, hearing aids are P zinc-air (peel the tab and air switches it on), and everything from car keys to motherboards runs on C lithium 3-volt coins for the decade-long shelf life.
- Treat the drawer like medicine: coin cells are among the most dangerous small objects in a house with children - a swallowed lithium coin burns through tissue within hours, and severe injuries and deaths have driven the industry toward child-resistant packaging. Tape spare coins, keep blister packs closed, and store them up high, the way you would store pills.
Frequently asked questions
Is LR44 the same as SR44?
Physically identical - same 11.6 mm diameter, same 5.4 mm height - but chemically different: LR44 is alkaline (L), SR44 is silver oxide (S). Silver oxide holds a nearly flat 1.55-volt curve until it dies, while alkaline voltage slides down steadily under load. A remote will never notice the difference; a watch, thermometer or light meter calibrated for the flat curve will run slow or misread on alkaline. The safe rule: substitute LR for SR only in cost-driven, precision-indifferent devices, never the other way around, and keep genuine SR cells in anything that measures.
What does CR2032 mean on a battery?
C is the chemistry (lithium manganese dioxide, 3 volts), R means round, 20 is the diameter in millimeters, and 32 is the height in tenths of a millimeter - so 3.2 mm. The same scheme reads every coin: CR2025 is a 2.5 mm-tall sibling, CR2016 a 1.6 mm one, and the cross-compatibility ends where the thickness differs, because spring-loaded contacts and fob cavities are cut for an exact height. A CR2032's combination of 3 volts, a decade of shelf life and a safe solid-state chemistry is why it became the default for car keys, scales, fitness gadgets and motherboard RTC clocks.
Can I use a 3V battery instead of 1.5V?
No - doubling the voltage is not an upgrade, it is a different contract. Devices regulate or resist for the voltage on the label; a 3-volt lithium coin in a 1.5-volt slot can push current through circuits designed for half of it, damaging the device or the cell (some lithium chemistries are unsafe when forced to discharge too hard). The 1.5-volt lithium coins that do exist (F chemistry, iron disulfide) are built for this - 1.5 V nominal in lithium chemistry. The only safe substitution within a size is between same-voltage chemistries, like LR44 alkaline and SR44 silver, with the discharge-curve caveat above.
Why were mercury button cells banned?
Mercury oxide cells (codes M and N) delivered a rock-steady 1.35 volts, which made them the precision standard for decades - and their toxic heavy metal made them an environmental liability from production through disposal. International restrictions phased them out, and manufacturers responded by re-engineering the instruments, not the chemistry: old exposure meters and thermometers calibrated for 1.35 V either accept zinc-air replacements with a similar curve or need recalibration. If an old device's manual asks for an MR-9 or PX625, that is the withdrawn chemistry - the modern answer is a zinc-air adapter cell, not a hunt for banned stock.