I don't mean to sound ignorant, but why bother with the hassle of hard-wiring it. The ciglighter/power port on your vehicle is more than likely shielded from the electronic interference associated with the cars electrical system/alternator where attempting to wire it off the battery directly could potentially cause problems without a filter on it, plus a fuse to ensure your radio doesn't melt in your hand.
My suggestion, if power outlets are a concern, go to wal mart and buy a tri port adapter for your ciglighter. You then have plenty of ports to hook up your mobile goodies, and it will only run you about 10-12 bucks and 0%frustration. If outlets aren't your concern, you can buy the mobile adapter with selectable voltage output for about 10 bucks from wal mart as well. Either one would seem to make your life much easier.
Good luck, and dont put too much juice into that scanner.