Fast Charging "Homemade". What are the risks?

I lost my original Fast Charger in my school and now I'm without one. The problem is, that sometimes I need that great feature.
My question is, can I disassembly a random 9V charger and "adapt" a Micro-USB cable to it? Since the GS6 supports 9V I don't see a problem there. Or must I short some data pins in order to enable fast charging to not fry the device?