HELP: Battery Powered Inductive Circuit

Hello All,
I'm hoping someone smarter than myself can help me out with this one because I am bashing my head clean through a wall.

This is my inductive transmitter circuit. Essentially, I have an ATTINY45 generating a 180khz square wave which drives a MOSFET and subsequently drives a coil to transmit current to the receive antenna. Now, for the most part this circuit works fine on my bench power supply (barring when I drive it a bit to hard) HOWEVER, the minute I attach this to a 12 volt battery, either the polyfuse trips or, if I remove the polyfuse, the MOSFET goes disco inferno. I'm guessing this has something to do with transient current on the power lines feeding the board but I have no idea WTF is going on and how can I fix it?
Thank you all in advance!