Zareba SP30 Solar-Powered Low-Impedance 30-Mile Fence Controller Solar-powered low-impedance 30-miles fence controller Includes 6-volt gel cell battery with solar setting switch for optimal performance and battery life Can compensate for energy loss caused by vegetation or fence load Convenient carry handle and versatile mounting bracket for easy movement between locations 0.66 stored joules; 1/2 joule output at 300 ohms