It can certainly be used, but the power output of such a small battery is estimated to be very low and the electricity generated is difficult to use elsewhere.
At present, for polycrystalline silicon solar cells, the maximum output power of mass-produced 156 × 156mm cells is just over 4W, with a voltage of 0.6 V and a current of 8 A. This requires many cells. series to achieve a relatively high voltage.
The solar cells used in the calculator are probably thin film cells. Compared with polycrystalline silicon solar cells, the output power is lower in the same area.
2-5 hours
Under direct sunlight of 5,000-10,000 lumens, it can be fully charged in 2-5 hours. The battery life of light-powered watches is typically 10 to 12 years. When it is completely ccharged (displayed H), it can work normally in the dark for about 6 months. In power saving standby mode, it takes about 16-20 months. Watches with backlight will display based on the backlight usage rate. Operating time can be reduced if necessary