I'm with Ymeski with the corrosion...also check your frame ground and your starter ground. a short to ground will cause a drain.
08 FX4... Flowmaster Exhaust, line-X, Sky Jacker leveling kit. 295/65/20 Nitto trails mounted on 20 X 9 Carroll Shelby wheels. AIRAID CAI. Harley headlamps and LED Tails & 3rd brake lights,custom upper and lower Grill. Edge Evolution. Interior/Exterior LED lighting, NFAB step bars, America Tri-fold Tonneau cover.