It is often through combining these different power sources that we find truly successful power sources.
Batteries are a reliable, consistent, and well-understood technology.
Unfortunately, power demands for satellites tend to be so high that a battery that would be strong enough to power a satellite for the length of a mission would be larger than the satellite itself. Thus, batteries tend to be used as temporary storage points for power from another source. Solar panels, especially the modern ones, provide abundant power for nearly all a satellite's needs and are safe and clean to launch. They are rather expensive to build and put into space. They need to always be pointed at the Sun, which means they aren't useful when blocked by planets or other objects .