This is all about learning OneWire communications. I'm able to make a small "adapter" playing the "man in the middle" hack between dell laptop and its power brick to provide "fake" wattage information. For me I'm using it to "fix" a power adapter which has a damaged identification chip. Of course it can also be used to use non-dell power adapter (on your own risk of damaging the laptop, or even burn your house, who knows...)
All the code and pcb design can be found at https://github.com/HclX/DELL_POWER_SPOOFER.git and my http://hclxing.wordpress.com/2014/02/26/hacking-a-dell-power-adapter-final-not-really/
Some pictures:
schematic:
pcb layout:
final populated pcb, toner transferred and hand soldered, some of the parts are salvaged from old dvd rom pcb:
dc jack from a broken dell laptop, it took me a fair amount of work to cut the pcb into that shape using my dremel so I can solder the dc jack
connecting with a working power adapter
to prove it's working, i'm faking my working 90W adapter as 65W
There is still work to do like enabling push button to import data from the connected working adapter, or switching between multiple imported data, making use the led indicator, ...