Quartz watch battery types and service life

There are roughly three types of quartz watch batteries:
　　1, alkaline batteries   LR
　　2, silver oxide batteries   SR
　　3, lithium batteries   CR or LI
　　　　
　　The voltage of ordinary dry cells decreases gradually with use, whereas the voltage of a silver oxide battery only drops abruptly when its lifespan is near its end. This characteristic is extremely beneficial for ensuring the timekeeping accuracy of quartz watches. However, the resulting issue is that one cannot simply measure the battery voltage to determine whether the charge is sufficient, and it is said that there is still no quick or non-destructive instrument available to make this measurement.

　　Silver oxide batteries are distinguished between high-current output and low-current output types, and the correct type must be determined according to the watch type. If a watch features an alarm function or a small illumination light, a high-current battery should be used (such as digital display quartz watches). Most quartz watches use low-current ones, and replacements must strictly follow the specified model. Randomly using a battery simply because the external dimensions match will cause the watch to malfunction; the power consumption of lighting the dial and sounding the alarm is thousands of times greater than the power consumption during normal timekeeping. Therefore, to extend battery life, minimise the use of the light and alarm functions. Letters following the battery model: SW denotes low-current output, used for analogue quartz watches; W denotes high-current output, used for digital quartz watches with alarms or lights.

　　Good-quality batteries feature a bright, polished surface with clear trademark and letter imprints, and a production date printed on the side. Counterfeit batteries are generally cruder, with blurred markings and an extremely short lifespan. Well-known watch battery brands include Switzerland's RENATA (each battery is independently packaged) and Japan's SEIKO, both of which offer good quality, whilst a better domestic brand is Changzhou's Dali. Good quartz watches must use quality batteries, as inferior batteries often cause damage to the watch.

　　The service life of a battery is related to two factors: 1, the battery capacity itself; the larger the battery capacity and the lower the power consumption, the longer the service life. 2, the power consumption of the watch circuitry. Currently, the power consumption of quartz watches is around 1 microamps, and battery capacities are generally between 4 and 40 mAh, with lithium batteries having a slightly larger capacity. Generally speaking, smaller watches house smaller batteries with correspondingly smaller capacities and shorter lifespans; two-hand watches are more battery-efficient than those with three or more hands. Regardless, under normal use, a battery should guarantee a lifespan of at least one year. If a watch requires frequent battery replacements, one must consider whether there is a fault in the circuit.

　　Battery leakage, alkali creep and gas expansion are common quality issues. The alkaline electrolyte inside the battery (sodium hydroxide or potassium hydroxide) can severely corrode the movement, causing parts to rust and fail (I once had a RADO watch where battery leakage corroded the dial, and I later spent over 500 to replace that dial), resulting in open circuits. Watches that have stopped due to a dead battery, or those stored unused for a long period, should have their batteries removed wherever possible to prevent leakage and gas expansion. According to statistics, over half of quartz watch faults are caused by the battery. Therefore, when your watch needs a battery replacement, you must choose a high-quality battery and have it replaced at a reliable watch repair shop.

　　Silver oxide batteries exhibit self-discharge even when not in use, and humid or high-temperature environments will increase this self-discharge. They should be stored in cool, dry conditions. Watches left unused for long periods should have their crowns pulled out (two-hand watches do not need this). At temperatures below 0 °C, the current output of the battery becomes very weak, affecting functions such as illumination, alarms and digital display windows on quartz watches.

　　Silver oxide batteries must not be charged or exposed to fire, and care should be taken not to cause short circuits during storage and installation. Used batteries from watch repair shops should be collected and disposed of centrally to prevent environmental pollution.