Automatic watches are charged by movement. These watches do not contain batteries. By moving the watch as it is worn on the wrist, power is stored within a spring in the watch. When fully charged, the power reserve typically lasts between 24-48 hours depending on the movement. If an automatic watch is fully charged and then not moved, it will run out of charge within this time.
When an automatic watch stops completely after running out of charge, it should be 'initiated' by winding it manually. This means turning the crown clockwise approximately 20-30 times. If an automatic watch is not initiated after stopping, it may run out of charge, slow down, or keep stopping and starting.
Always re-initiate your automatic watch after it stops completely.
The amount of an automatic watch is charged can be increased by wearing a tight fitting strap - so the internal parts of the watch move and charge the movement, rather than having just the watch itself moving.
It should also be noted that automatic watches are generally not as accurate as quartz watches. It is not abnormal to notice time variances of -45 to +45 seconds per day. More expensive Swiss models, e.g. ETA or Valjoux movements, will have a greater degree of daily accuracy.
It may seem strange for your watch to speed up when the power runs down, but it's perfectly normal.
Energy released from the mainspring causes the balance wheel to turn back and forth. That oscillating motion is how a watch measures time. As a rule, the steadier the rate of oscillation, the more accurate the timekeeping will be. However, the rate can fluctuate depending on how much power is stored in the mainspring.
Typically, a watch's rate is steadiest when the power reserve is above 90 percent. When the energy level drops below that point, it very slowly beings to lose the torque needed to fully drive the balance wheel. This causes a drop in amplitude, which is the number of degrees that the balance wheel rotates each time it turns. When this happens, the rotations become shorter and take less time to complete. As a result, the rate increases, and your watch speeds up.
To get the best performance from your mechanical watch, IT'S ALL ABOUT THE POWER!
What are the major factors influencing accuracy?
Mechanical watches have a mechanism that is moved by power generated as the mainspring unwinds, and small metal parts that work together to control accuracy. The fragile metal parts of a mechanical watch are easily influenced by environmental factors such as temperature, gravity, and shock. Also, conditions of use such as regular usage time, movements of your arm and winding state of the mainspring can influence the gain / loss of the watch.
Do not place the watch where the temperature is extremely low / high (less than 5ºC or more than 35ºC). Mechanical watch parts are metal and slightly expand and contract with changes in temperature, and this influences accuracy. Normally, under high temperatures, a watch tends to lose time, and under low temperatures, it tends to gain time.
Keep the watch away from magnetic fields. Watches can be adversely affected by magnetism and may gain or lose time. It is important not to leave a watch close to magnetic objects for a long time. In particular, cell phones, television and PC speakers, magnetic necklaces, handbag clasps, hair-driers, electric razors, magnetic parts of refrigerators are all magnetic. An affected watch remains magnetically charged even after being removed from the magnetic source.
Strong shock may affect accuracy. It is recommended that you remove your watch before playing any sport that involves strong impacts. Any direct impact to your wrists can affect the very small parts inside the watch. Dropping the watch may also cause damage.
The accuracy of the watch is affected by its position when it is not worn on the wrist. The rates of loss / gain of mechanical watches vary slightly depending on positions they are put in, such as being placed horizontally with its face or back turned up, or being laid on its 12:00 / 3:00 / 6:00 / 9:00 side respectively. This is because gravity affects the operation of the inside movement of the watch. Experiment with storing the watch in various positions for 7 to 8 hours when not in use and check the loss / gain of each position. By storing the watch in a resting position that minimizes loss / gain you may counteract the loss/ gain which occurs while the watch is being worn.