The 12v socket in the rear on my vehicle states 320W max next to it yet its fused with a 15A fuse. Basic school physics ( Power = Voltage x Current) tells me it cannot output 320W the power is 12V x 15A = 180 W so the max power you can draw before the fuse blows is 180W. I tried this with a device I knew drew over 200W and sure enough the 15A fuse blew. Why have they stated you can draw 320W from the socket ???