The solar panel of the calculator is made of amorphous silicon. In low light conditions, current output is also possible. However, the conversion efficiency of amorphous silicon is very low. The calculator consumes very little power and hence amorphous silicon can meet the requirements;
Solar panels used in mobile power supplies are made of polycrystalline silicon or monocrystalline silicon. High conversion efficiency. In low light conditions, the conversion efficiency is low. Indoors, without sunlight, there is almost no current production. In cloudy conditions, there is some current output, but the output current is very small.
Therefore, charging a solar power bank on a cloudy day has no obvious effect. Must be charged in bright sunlight conditions.
On cloudy days we can also see the source oflight, but the conversion rate of this light for photovoltaic solar panels is very low because the light intensity is not enough if the light is seen through the taillights of the charging car. If the intensity is not as strong as the outdoor light intensity on a cloudy day, the charging effect will be very small, almost zero. Because the light conversion rate of the best photovoltaic solar panels is less than 20% and the sun exposure is insufficient, the consequences can be imagined.