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If you have a watch SR626SW battery that isn't working, you may be wondering how to test it. In this post, we'll learn, how to use a multimeter to test the watch battery.We'll also give you some tips on how to extend the life of your watch battery.Keep reading!

How to Test a 377 / SR626SW Watch Battery with a Multimeter

Contents

Know Your Watch Battery: 377 / SR626SW Basics
Tools You'll Need
Step 1: Open-Circuit Voltage (OCV) Test
Step 2: Loaded Test (With a Resistor)
How to Interpret Results (Threshold Table)
Common Mistakes & Real-World Pitfalls
Recommended Brands & Freshness Checks
Common Misconceptions from Online Guides
FAQs

Know Your Watch Battery: 377 / SR626SW Basics

SR626SW battery is a small circular silver oxide button battery. It is usually used for color, small electronic bias, especially for watches. The "SR" in the name represents rechargeable tableware oxide, "626" indicates its size (circumference 6.8 millimeters, height 2.6 millimeters), and "SW" indicates its low displacement, suitable for watch operation.

Features and Characteristics of SR626SW Battery

Small and compact design
High energy density
Stable voltage output
Long shelf life
Mercury-free composition
Non-rechargeable

Technical Specifications of SR626SW Battery

Specification	Details
Type	Silver Oxide (Ag2O)
Diameter	6.8 mm (0.27 inches)
Height	2.6 mm (0.10 inches)
Voltage	1.55 volts
Capacity	Approximately 9-20 mAh
Chemistry	Silver oxide
Operating Temperature	-20°C to +60°C
Weight	About 1.5 grams
Shelf Life	3-5 years

Tip:The SR626SW isnotinterchangeable with LR626 (alkaline) or CR-type lithium cells. Although the size may appear identical, their chemistries, voltages, and discharge curves differ significantly.

Tools You'll Need

Digital multimeter (auto-ranging DC volts)
Mini alligator clips or precision probes
Load resistor:1 kΩ for quick screening; 3.3 – 10 kΩ for gentler testing
Clean, lint-free cloth to remove oxidation on contacts

Why a load resistor?

Because a 1k Ω resistor consumes approximately 1.5mA at 1.55V, which is much higher than the μ a level current of a watch. This will exaggerate the voltage drop, expose internal resistance, or cause premature aging.

How to use a multimeter to test watch batteries

Step 1: Open-Circuit Voltage (OCV) Test

Set the multimeter to DC volts (2 V range or auto).
Touch the red probe (+) to the battery's flat top and black probe (–) to the bottom case.
Record the reading. A fresh cell should show ≈ 1.55 – 1.60 V with no load.

[Diagram placeholder] Probe placement for measuring 377/SR626SW OCV - top is positive terminal.

Open-Circuit Voltage (OCV) Test

Step 2: Loaded Test (With a Resistor)

This method reveals internal resistance and voltage stability under realistic pulse loads.

Connect a 1 kΩ resistor across the cell and measure voltage simultaneously.
A healthy 377 battery should stay near 1.50 V or higher under load.
If voltage drops below ≈ 1.35 V, the cell is weak and should be replaced.

Caution:Never short-circuit a coin cell. Always use a resistor to limit current and avoid overheating.

How to Interpret Results (Threshold Table)

Condition	OCV	1 kΩ Loaded	Status
Fresh cell	1.55 – 1.60 V	≥ 1.50 V	Good - ready to use
Moderate aging	1.50 – 1.55 V	1.40 – 1.48 V	Usable but replace soon
High internal resistance	≥ 1.50 V	≤ 1.35 V	Replace - will fail under pulse load
End-of-life	< 1.50 V	< 1.30 V	Depleted

Common Mistakes & Real-World Pitfalls

Confusing chemistries:SR626SW (1.55 V silver oxide) is not the same as LR626/AG4 (alkaline) or CR (lithium 3 V).
Ignoring drain class:SW for low-drain watches; W for high-drain chronographs.
Only checking OCV:A battery can show 1.55 V open-circuit but collapse under load.
Dirty contacts or oxidation:Can mimic a weak battery reading - clean before testing.
Old stock:Always verify production date and buy from trusted sources.

Recommended Brands & Freshness Checks

Reputable manufacturers such asRenata,Murata (Sony),Maxell,Energizer, andPanasonicmaintain tight tolerances for SR626SW (377) cells. Their datasheets confirm 1.55 V nominal voltage, stable flat discharge curves, and approximately 24–28 mAh capacity per IEC 60086-3 standard.

Common Misconceptions from Online Guides

Several online tutorials describe a simplified process for testing watch batteries with a multimeter - for example, setting the meter to DC voltage, touching the probes to the terminals, and expecting a reading between 1.5 V and 3 V. While this method works for general batteries such as AA, AAA, or CR2032 lithium cells, it's not technically accurate for silver-oxide watch cells like SR626SW / 377.

The SR626SW operates at a nominal voltage of 1.55 V and follows a very flat discharge curve. Even when it's nearly exhausted, it often still shows around 1.50 V on an open-circuit reading. This means a "simple" test that looks only at the voltage can easily misjudge a weak battery as healthy.

To correctly evaluate a watch battery, professionals use a loaded voltage test - applying a resistor (e.g., 1 kΩ) across the terminals while measuring voltage. A good SR626SW will stay above about 1.50 V under load, while a cell that drops to 1.35 V or below is aging or nearly depleted.

Method	Description	Problem	Better Practice
"1.5–3V OK" quick check	Generic guide for all coin cells	Misleading: SR626SW is 1.55V, not 3V	Use SR626SW-specific thresholds (1.55V ±0.05V)
OCV only (no load)	Measure voltage with no resistor	Hides high internal resistance	Measure again under 1 kΩ load
No chemistry distinction	Treats all button cells the same	Confuses silver-oxide vs lithium vs alkaline	Confirm chemistry: SR = silver oxide, LR = alkaline, CR = lithium

Summary: General tutorials (such as those for CR2032 or AA cells) are fine for rough testing, but watch batteries like 377 / SR626SW require both open-circuit and loaded checks to reveal true condition. If the voltage drops below 1.35 V under load, the cell should be replaced even if it still reads 1.5 V open-circuit.