The Nomad 20 Solar Panel from Goal Zero is a solar panel for charging Goal Zero Sherpa 50/100 Power Packs, Yeti 150/400 Solar Generators, and compatible USB and 12V devices like cellphones, GPS, and iPods. It features monocrystalline silicon cells capable of producing 20W of electrical power with an open circuit voltage from 18 to 22 Volts. The cells of the solar panel are made of monocrystalline silicon which provides a higher conversion efficiency rates than polycrystalline silicon because it is made out of the higher-grade material. At the back of the panel, you will find output power hub with four pig-tailed connectors: a standard power USB output, a 2.5 mm Mini Solar Port, a female-type 8 mm blue-coded Solar Port, and a male-type 8 mm blue-coded Solar Port. The USB and Mini Solar ports have built-in regulators to provide constant power outputs. While the male-type 8 mm blue-coded Solar Port provides an open circuit voltage of 18-22V and can be used for charging select devices, the female-type 8 mm Solar Port can only be used for in series connection with a maximum of three other Nomad 20 Panels. These four units connected in series may be used when a high total output power or a significant reduction in charging times are needed.