A 1620 battery is a 3V lithium coin cell measuring 16mm across by 2.0mm thick, and it fits many slim analog watches that draw very little current. The exact fit depends on the movement and the compartment depth, so matching the printed code before swapping saves a cracked case back and a wasted afternoon. Most owners who confirm the marking on the old cell end up with a reliable fix.
Below you’ll find sizing notes, equivalent labels, and the safe way to swap one in. The goal is to help you confirm fit, source a fresh cell, and avoid the common mistakes that turn a five-minute job into a trip to the repair bench.
The 1620 Battery and Where It Fits in Watch Power
Coin cells get their model numbers from their physical size in millimeters, so a 1620 measures 16mm wide by 2.0mm tall. That thin profile makes it one of the slimmest lithium cells still shipping for watch compartments, and it slots into movements designed for low continuous drain. Watch designers chose it because analog quartz movements sip microamps rather than gulp them.
Most analog watches that accept a 1620 pull somewhere in the range of 1 to 3 microamps during normal operation. That tiny demand is why a single cell can keep a watch running for years. The trade-off is straightforward: thinner cells hold less active material, so capacity drops compared to thicker cousins like the 2032.
Why the 2.0mm Profile Matters
The compartment inside a watch case has a fixed depth, and a battery taller than spec will press against the case back. A 1620 leaves just enough clearance for a proper gasket seal and a contact spring under light pressure. Going thicker by even a millimeter is the difference between a flush closure and a bowed back that lets moisture in.
CR1620, BR1620, and the Other Names You May See on the Shelf
Cross-reference labels on store shelves often confuse first-time buyers, but the differences usually come down to chemistry and manufacturer branding. A CR1620 is the standard lithium-manganese dioxide cell that fits nearly every watch using this form factor. Energizer, Duracell, Renata, Sony, and Maxell all sell versions of it under their own labels.
| Label | Chemistry | Watch Use |
|---|---|---|
| CR1620 | Lithium manganese dioxide | Standard analog and digital watches |
| BR1620 | Lithium polycarbon monofluoride | Wider temperature range, lower peak capacity |
| DL1620 | Lithium manganese dioxide | Duracell house label, same as CR1620 |
| ECR1620 | Lithium manganese dioxide | Energizer house label, same as CR1620 |
| 1620-1W | Lithium manganese dioxide | Generic retailer code, same physical cell |
A BR1620 swaps in without issue when a CR1620 is called for, but its operating temperature range stretches wider and its capacity runs a touch lower. For a wristwatch worn indoors, the two are functionally interchangeable. Outdoor instruments exposed to deep cold or engine heat sometimes specify BR chemistry for that reason.
That chemistry distinction matters more when the cell moves from wrist to dashboard or outdoor sensor.
Tip: any label carrying the four digits “1620” after a two-letter prefix refers to the same 16mm by 2.0mm cell, so match the diameter and thickness, not the prefix.
Why the 1620 and 1632 Are Not Interchangeable
Both cells share the same 16mm diameter and the same 3V output, but the 1632 measures 3.2mm tall instead of 2.0mm. That extra 1.2mm of height is the entire reason a 1632 will not seat properly inside a compartment built for a 1620. The chemistry and the diameter being identical makes the mistake easy to commit, which is why it shows up so often on repair benches.
What Happens When a Thicker Cell Gets Forced In
A 1632 dropped into a 1620 compartment often bows the case back outward and prevents the gasket from sealing evenly. Over time, that pressure can crack the battery clip, deform the contact spring, or jam the movement’s second hand. Moisture then has a straight path past a compromised seal, and corrosion follows.
The reverse swap, a 1620 in a 1632 compartment, leaves a 1.2mm gap that lets the cell rattle and lose contact during movement. Neither outcome is worth the savings on a slightly cheaper or slightly thicker cell.
Confirming a 1620 Is the Correct Cell for Your Watch
The single best way to confirm fit is to read the marking printed on the existing battery before ordering a replacement. Manufacturers etch the model number into the top face, so a quick glance under good light resolves the question in seconds. When the old cell is missing or unreadable, two fallback checks help fill in the gap.
Measure the Compartment Depth
Calipers set to millimeters tell the whole story once the case back is off. A measurement between 1.9mm and 2.1mm points to a 1620 fit, while anything closer to 3mm means a thicker cell belongs there. Eyeballing without tools works in a pinch, but a 1.2mm difference is hard to judge by feel alone.
Cross-Check Against the Watch Maker’s Service Sheet
Seiko, Citizen, and other major brands publish technical sheets that list the exact battery for each caliber. A retailer compatibility chart on a parts site adds a second opinion and often includes movement numbers rather than full model names. Two matches between independent sources rule out the kind of guess that ends with a cracked clip.
Capacity, Shelf Life, and Real-World Longevity
Most CR1620 cells ship with a rated capacity between 60 and 80 mAh, depending on the brand and the production lot. That number reflects what the cell can deliver under specific load conditions, so real-world life in a watch depends on how hard the movement pulls. A simple analog movement at room temperature stretches a 1620 to its full potential.
| Metric | Typical Range |
|---|---|
| Rated capacity | 60 to 80 mAh |
| Shelf life (uninstalled) | 8 to 10 years |
| Service life in watch | 2 to 4 years |
| Operating temperature | -30C to 60C |
Uninstalled shelf life runs about 8 to 10 years when stored at room temperature in original packaging. The IEC 60086 standard covers coin cell testing, so any cell marked with the rated capacity on the back has been through a defined discharge protocol. Inside a working watch, expect roughly 2 to 4 years of service before voltage drops low enough to slow the second hand or skip a beat.
Once you’ve confirmed the right cell, the next question is how long it will actually last on the wrist.
Sourcing a Replacement and Swapping It Safely
Specialty watch dealers, electronics parts suppliers, and major pharmacies all carry 1620 cells in single or multi-packs. A Renata cell from a watch supply house tends to cost more than a bulk pack from a parts retailer, but both ship the same physical battery. Match the expiration date on the blister pack to at least four years out to avoid installing an already-weakened cell.
Tools That Protect the Cell and the Watch
- Non-metallic case opener prevents scratches on the case back and keeps the gasket from getting nicked.
- Plastic tweezers keep skin oils off the new cell’s faces during handling.
- Soft cloth tray catches any tiny screw if the back is a screw-down style.
- Multimeter confirms the new cell delivers its rated voltage before you seal the case.
Lining up these tools before starting keeps the swap under five minutes for most movements.
Polarity and Seating
The positive terminal faces up on nearly every coin cell watch, and a small “+” engraved into the compartment floor confirms the orientation. Press the cell flat with a plastic tool until the contact spring seats, then replace the gasket and close the case back. A quick resistance check with a multimeter across the terminals confirms the cell is delivering its rated voltage before the case is sealed.
That voltage check catches most swaps, but a few errors still slip through and need undoing.
Warning: never stack a spacer or shim under a cell to fill a gap left by a wrong size, and never bend the contact spring outward to compensate for a loose fit.
Common Fitment Errors and How to Recover From Them
Substituting a 1632, 1616, or 2016 will either leave a gap or prevent the case back from closing flush. Each of those cells carries the same 3V rating, which is exactly what makes the swap tempting when a 1620 is out of stock. The diameter match is not the same as a height match, so the result is almost always a problem rather than a fix.
Voltage Reads Fine but the Watch Stops
A battery that shows correct voltage on a tester but fails under load often indicates an old stock cell, not a faulty movement. Loaded voltage testing under a 1k ohm resistor reveals the true state of a depleted cell that an open-circuit reading can hide. Swapping in a fresh, in-date battery from a different lot is the fastest way to confirm the diagnosis.
Still No Start After a Fresh 1620
If the watch will not start after a brand new 1620 is installed, inspect the contact spring and gasket before assuming battery failure. A bent spring loses pressure on the cell, and a pinched gasket can push the case back just enough to break contact. Cleaning the contact with a cotton swab and a tiny amount of isopropyl alcohol usually restores the connection.
A movement that draws current on a multimeter but refuses to keep time points toward coil damage or a dried lubricant, both of which need a bench service. At that stage, taking the watch to a watchmaker saves the movement and avoids the cost of a replacement that would face the same fate.
The Bottom Line
A 1620 battery is a slim 3V lithium coin cell that powers many analog watches, and confirming the exact fit before swapping protects both the case and the movement. Match the printed code on the old cell, watch the thickness, and avoid the tempting 1632 substitution that ends in a cracked clip. A fresh cell from a reputable brand, installed with non-metallic tools, keeps the watch running for another two to four years.
FAQ
Is a 1620 battery the same as a CR1620?
Both labels describe a single coin cell built around lithium-manganese dioxide chemistry in an identical 16mm by 2.0mm metal case.0mm cell. Cross-reference labels like DL1620 and ECR1620 are manufacturer equivalents of the same physical battery.
Can I use a CR2016 instead of a 1620 in my watch?
A CR2016 is 20mm wide and will not fit a compartment built for a 16mm cell. Even if it seated, the thinner profile leaves a gap that breaks contact during wrist movement, so the substitution fails on size alone.
How long does a 1620 watch battery last?
Inside a working watch, expect roughly 2 to 4 years of service before the voltage drops low enough to slow the second hand. Uninstalled shelf life runs about 8 to 10 years when stored at room temperature in original packaging.
What size is a 1620 battery?
Diameter clocks in at 16mm with a slim 2.0mm thickness, matching the common CR1620 footprint.0mm in height. Coin cell model numbers reflect these dimensions directly, so any four-digit label ending in 20 refers to the same thin profile.
Are 1620 and 1632 batteries interchangeable in watches?
No, the 1620 and 1632 share the same 16mm diameter but differ in thickness, with the 1632 measuring 3.2mm tall. A 1632 forced into a 1620 compartment bows the case back and can crack the battery clip.
Where can I buy a replacement 1620 watch battery?
Specialty watch dealers, electronics parts suppliers, and major pharmacies all carry 1620 cells in single or multi-packs. Renata, Energizer, Duracell, and Maxell versions are widely available and ship the same physical cell under different labels.
