PV and solar power systems convert light into electricity. They are the building blocks of photovoltaic (PV) modules. There are many different types of PV and solar power systems. Examples include solar batteries, solar battery chargers, and solar panels. A solar battery is a sealed, maintenance-free device. A solar battery charger can be used to power devices such as radio receivers, lighting, and radio modems. A solar panel is a device that converts energy from the sun into usable forms, either by absorbing the sun’s heat directly, or by converting its light into electricity. A photovoltaic system or PV system may include a battery backup or uninterruptible power supply (UPS) that can operate selected circuits for hours or even days. PV and solar power systems also include products such as solar arrays.