A solar system consists of 3 major components: solar panel (converts sunlight into DC electricity), storage battery (to store accumulated energy), and controller (the intelligence of the system). The controller is responsible for accepting electricity from the soar panel, using that electricity to keep the storage battery charged (without overcharging it), and providing current to the lights or other loads.
Unlike inexpensive controllers, which have a couple of LEDs to indicate proper functions, this controller has an LCD display panel, which provides information to the user on voltage and current levels, charging and discharging of storage. It is programmable for different lead acid batteries and voltages using a microprocessor. It is protected against over/under/reversed voltage. It is designed to provide up to 30 amps of current.
We will be using it to control the 12 volt solar system on our barn, which is used in the event of a power outage and for other purposes.