In a DC-coupled system a charge controller is connected to the photovoltaic system. The solar charge controller regulates the flow of energy into the battery and ensures, that the battery receives sufficient charge. A battery inverter is responsible for inverting the DC current to AC current that can be consumed by AC loads on site. DC loads should be supplied via the load output of the charge controller. It incorporates a LVD (low voltage disconnect) function, protecting the battery from the dangers of deep discharge.
In an AC-coupled system solar modules are connected to the DC input of a PV inverter. Direct current (DC) from the solar modules is converted into alternating current (AC), when the output of the PV inverter is connected to an AC source. The battery inverter will create this local AC source. Energy from the solar system can now supply electric loads. Surplus energy will be used to charge the batteries. Power control in such a system is enabled by frequency shifting or droop control. The battery inverter by means of its electronic control systems is able to regulate the power output of the PV inverter. Power control is necessary to prevent overcharging of the batteries.
Both technologies have advantages and limitations. I'll be happy to assist you in finding the optimum technical solution based on your specific requirements.