I have an HP laptop, and the HP laptop charger appears to have 3-pins on the plug. I believe one pin is ground/common, one pin is +18.5V, and the other pin is some sort of communication channel between the laptop and the charger.
I also have a 12 volt laptop car power adaptor that I am keen to use to charge my laptop on occasion. It is capable of outputting 19V, which the laptop will accept. But it only has two wires, common/ground, and positive.
What I want to do is cut into the existing 18.5V power cable on the original mains charger and join the cable onto the 12volt car charger. I am unable to do this from the standard "multi-adaptor" end that was originally on the 12volt adaptor because it didn't come with the appropriate connector for my laptop, hence why I want to use the existing cable.
My question is really: the middle core in the cable which is used to communicate between the laptop and the charger; is it advisable to leave that wire out? The reason I ask is that 12volt car/laptop charger obviously doesn't have this communication wire.
What would happen if I didn't have this 'middle pin/communication wire' connected to anything? Would my laptop blow up, would it over charge?
Any info/help would be greatly appreciated! :-)