It is possible to use a solar panel to charge your ring doorbell. However, it is important to note that the amount of power that can be generated by a solar panel depends on many factors, including the size and efficiency of the panel, the amount of sunlight that hits it, and the temperature. Because of this, it is difficult to say how long it would take to fully charge your ring doorbell with a solar panel. In general, however, it is best to use an AC adapter to charge your ring doorbell, as this will provide a steadier supply of power.