Most quartz watches use a silver oxide battery, which is small in size, large in capacity and stable in output voltage, making it ideal for use on quartz watches. There are also many specifications and types of batteries for quartz watches. In addition to silver oxide batteries, there are lithium batteries and alkaline batteries. Generally speaking, the capacity of the battery is related to its volume. The larger the volume, the larger the capacity. The battery capacity also determines the service life of the battery.
Instrumentation for measuring the battery performance of a watch
Unlike ordinary dry batteries, the discharge curve of a silver oxide battery is very flat. It does not have a voltage that gradually decreases with the use of a dry battery (see photo). This is of course beneficial for maintaining the watch's travel accuracy. But it also brings a problem, that is, you can't judge the battery capacity by measuring the voltage. The nominal voltage of the silver oxide battery is basically 1.55V, and this voltage will be maintained until the end of the battery life. Once the battery voltage begins to drop, its service life will soon arrive, so in order to avoid affecting the normal wearing of the watch, many quartz watches are equipped with a battery voltage warning function, which is stopped by the second hand for 4 seconds, and then jumped 4 times. Once this happens, the watch can still move about 10 days, reminding you to replace the battery immediately. This function is also called "E.O.L", but there is no such thing as a quartz watch without a center second hand.
In fact, like all batteries, the new battery capacity is not exactly the same, the unit of battery capacity is expressed in milliampere hours (maH). So far, I have not heard of an instrument that can quickly, non-destructively and accurately detect the capacity of a silver oxide battery. As early as 20 years ago, I heard that foreign countries have used heavy money to reward such equipment. Invention, but still no one can still make it.
When the battery manufacturer performs the battery quality inspection, it still uses the experiment of discharging the battery in batches. It is to connect a load to the battery under test to form a closed loop of a certain current. When the voltage of the battery is reduced to a certain value, The discharge current multiplied by the discharge time is the actual capacity of the battery. When the experiment is over, the battery is also scrapped.
Now the method of quickly detecting the watch battery is heavy load discharge, see the battery under different discharge currents, the voltage drop, because with the use, the internal resistance of the battery (also known as the internal resistance of the battery) will increase; As the discharge current increases, its closed circuit voltage also drops abruptly.