The Seiko Caliber VS43A is a solar-powered quartz movement with three hands and a day/date display. Epson’s revision 07 specification, dated 4 August 2023, lists about 12 months of operation after a full charge, accuracy of ±20 seconds per month on wrist, and a rechargeable secondary cell—not a conventional disposable watch battery. Those are component specifications, not a guarantee of performance in every finished watch.
What the VS43A is
The VS43A is an analog solar quartz caliber: an amorphous-silicon solar cell converts light into electrical energy, which is stored in an installed rechargeable secondary cell. A 32,768 Hz tuning-fork quartz oscillator regulates timekeeping. The display is specified for hour, minute and second hands, plus day and date.
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Epson’s Cal. VS43A specification, revision 07, gives an outside diameter of 28.60 mm and a total height of 3.50 mm, including the secondary battery. These are movement dimensions; they do not establish that the caliber will fit a particular case or replace another movement without further checks.
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| Specification | Manufacturer-stated value |
|---|---|
| Movement type | Solar quartz |
| Display | Three hands; day and date |
| Accuracy | ±20 seconds per month on wrist |
| Operating temperature | −5°C to +50°C |
| Running time after full charge | Approximately 12 months |
| Outside diameter | 28.60 mm |
| Total height | 3.50 mm, including secondary battery |
| Quartz oscillator frequency | 32,768 Hz |
| Solar cell | Amorphous silicon |
The figures are from Epson’s revision 07 specification dated 4 August 2023. Earlier 2020/2021 document mirrors give a six-month running-time estimate; the later official revision gives approximately 12 months. Treat the estimate as specific to that specification, not as a prediction for every watch, dial, charging history or use pattern.
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- Includes individual box, instruction manual (English language not guaranteed)
- Solar
- Approximately 10 months when fully charged
- Average monthly difference ±15 seconds
- Calendar (date) function
How charging and low-charge warnings work
Charging time varies substantially with illumination. Epson lists the following approximate times to full charge under specified light conditions:
| Light condition in Epson specification | Approximate time to full charge |
|---|---|
| Sunlight at 100,000 lux | 5 hours |
| Fluorescent light at 3,000 lux | 47 hours |
These are manufacturer figures for the stated illumination, not universal charging promises. A watch’s dial and construction, the actual light reaching its solar cell, and how it is positioned can affect charging.
The specification describes a quick-start function: after exposure to light above 1,000 lux, operation begins within seconds. When voltage reaches the specified 1.10 V threshold, the seconds hand advances in two-second intervals as a depletion warning. The stated operation-stopping voltage is 1.0 V. If the hand is moving in two-second jumps, give the watch sustained exposure to suitable light rather than assuming it needs a disposable battery.
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The movement uses a rechargeable secondary cell. Epson lists the cell at 9.5 mm × 2.1 mm, nominal 1.5 V and 5.5 mAh, and identifies it as installed rechargeable energy storage. It should not be treated as an ordinary disposable silver-oxide cell.
A parts retailer associates cells in the MT920 family with the VS43A, but that listing alone does not confirm compatibility for every revision or watch configuration. Before ordering, verify the marking on the existing movement, its revision where available, the watch’s configuration, and the cell’s physical and electrical connection. Epson’s specification is the primary reference for the movement and listed components; the retailer listing is at Batterien-und-Akkus.com.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Replacing a VS43A movement or sourcing parts
A replacement movement is a repair component, not a guaranteed drop-in match based solely on the VS43A name. A retailer’s listing identifies a VS43 movement and says it is marked VS43A; that confirms the marking for that listing, not interchangeability across all watches. Check the complete movement marking and revision, case and dial fit, hand and calendar arrangement, and solar-cell connections before purchase.
Epson’s specification lists separate components including solar cell units 4020555 and 4020556, hand-setting stem 0351177, solar-cell lead terminals 4246524, hour-wheel spacer 0493500, and dial washer 0491735. Their presence in the specification does not establish that each part is suitable for every VS43A-equipped watch. The retailer movement listing is available at Somal Canada.
Watches using the VS43A
Nixon identifies an Epson VS43A movement on its Sentry Solar Stainless Steel product page. This is one documented application, not a complete list of watches using the caliber. When comparing watches or considering a repair, check the case dimensions, day/date layout, how much light reaches the solar cell, and the availability and compatibility of the exact replacement movement or cell. A shared caliber name by itself does not establish that parts interchange.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
