How to Check the Battery Capacity of Quartz Watches[/size]
Unlike conventional dry batteries, silver oxide batteries maintain a very stable discharge curve, not decreasing in voltage as they are used, which benefits the accuracy of quartz watches. However, this characteristic complicates the process of estimating the remaining battery capacity as the voltage stays around 1.55V until nearly the end of the battery’s life.
Quartz watches often come with a low battery warning feature, indicated by the second hand pausing for 4 seconds and then jumping forward 4 seconds rapidly. This signals that the watch can run for about 10 more days, suggesting an urgent battery replacement. This feature is known as “E.O.L” but is absent in quartz watches without a central second hand.
Battery capacity varies even among new batteries and is measured in milliampere-hours (maH). To date, no device can quickly, non-destructively, and accurately measure the capacity of silver oxide batteries. The traditional method involves batch discharging under a load until a certain voltage drop, which, unfortunately, renders the batteries useless afterward.
Rapid testing methods for quartz watch batteries involve high-load discharging, observing voltage drops under varying currents, as internal resistance increases with use. Swiss-made quartz watch testing devices sometimes include this testing feature, offering different load resistances for varying types of quartz watches.
For instance, Swiss-made watch calibrators may have load resistances of 2000 ohms, 50 ohms, and 5 ohms, accommodating watches with different power requirements—high current output types for LCD watches with lights and alarms, and low current output types for analog quartz watches.
By pressing a button to engage the load resistor, one can observe the immediate voltage drop, which should not fall below 1.35V. The battery’s size and the ambient temperature also affect the test results, with larger batteries and higher temperatures showing less voltage drop.
Although heavy load testing can estimate the battery’s capacity, it does not provide precise numerical measurements and should not be performed for extended periods to avoid significant energy depletion.
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