APOLLO S-210p series is stand-alone bidirectional inverter with capability to parallel output to expand power or increase reliability of PV system. It can be connected up to 10 inverters in parallel. Parallel inverter system are designed to have the advantage to increase output power and enhance reliability. It converts the DC power from the battery into AC power to supply to AC appliances. It can operates with solar charge controller in order to utilize solar energy or charge battery. This inverters operate in multi-master operation scheme thus there is not master unit and no external controller in system, each inverter equipped with microprocessor that makes it has high performance and efficiency. The inverters supply high quality pure sine wave power output with low harmonic distortion. It is suitable for stand-alone solar power system in remote area where reliability is important.