1) disassemble the original EN-4 battery (i used a swiss-knife)
2) desolder useless Ni-Cd cabled battery-pack
3) using a drill, make an hole (for the input plug)
4) with an hot-glue gun fix a female plug on the plastic base
5) solder wires respecting polarity
6) repack all plastic with instant-glue
7) attach the Li-Po battery with some strong double-sided tape
***USE 7,4 Li-Po (with lowest "C" as possible) or you'll burn your DSLR***
8) connect the plug and enjoy!