Power Management on aircraft (current limited) outlets

I've tried to use the outlets on several types of aircraft with my M4600 but haven't had any success. I can plug in the power supply (180 w), but as soon as I connect the power suply to the laptop, the outlet shuts off. I've tried the low power options and found that none of them make any difference. I connected the laptop using the standard power supply and found that when the battery is charged, the power draw is often not much greater than 50 W. (I had a KILL A WATT connected so I could see exactly how much power was being drawn.) I tried using a 65 W dell power supply from an old vostro laptop, but I found that the M4600 seemed to be very brain-damaged in the way it utilizes the reduced power. It slows down drastically (as expected), but only draws around 35 W, despite the power supply being able to supply 65 W. I noticed that Dell has a aircraft power supply, "Dell 65-Watt Auto / Air AC Adapter with Power Cord for Select Dell Inspiron / Latitude / Studio / Vostro / XPS Laptops / Precision Mobile WorkStations". Has anyone tried it? I'm wondering if it works any better than the vostro power supply. Has anyone figured out how to use a Precision laptop on an aircraft?