Watch Winder's Battery Life

Many users are also concerned about battery life of their watch winder. Unless you want to keep your precious timepiece in a safe without any power outlets, one should then be concern. Otherwise, like me, the AC mains would be eventually used for my homemade watch winder project.

Just out of interest, let’s see what the battery life of a watch winder would be like.

Example:-
1) A motor draws about 60mA when loaded with a watch in its winding cup.
2) At rest, the circuit draws about 4mA.
3) If I use 4xAA dry cells, it has capacity of about 2500mAH for 20mA loads.

In the 950TPD mode,
2500mAh/4mA = 625 x 39 = 24375/24 = 10156/30 = 33.8 months

Explanation: -
The motor does not continuously turn, meaning drawing continuous 60mA, so I’ve taken the minimum current for calculations. Note that the motor remains at rest about 90% of the time.

Here’s what I did…
Divide battery capacity with motor current, and then multiply by the ratio of the sequence (Total cycle time divide by ON time). I’ve used my own sequence for this calculation.

Next, I divide by 24 hours to determine the number of days.

Lastly, I divide by 30 days to know how many months the battery pack can power up this unit.

Theoretically, it should have enough juice for approximately more than 30 months, or about 2.5 years. (90% of 33.8 months).

From this exercise, you will noticed that battery life depends on 3 important factors:-
a) current drawn by the motor,
b) battery capacity, and
c) winding sequence ratio of ON and OFF times.

So, hypothetically if I have a higher battery capacity and a motor that draws lower current, I can perhaps extend the battery life. The winding sequence would then be dependant on the motor rpm.

Labels: DIY watch winder, winding sequence