After a few attempts to get the USB lighter housing/charging/battery stuff to work, I eventually gave up. I was trying to use a MOSFET connected to one of the arduino pins to power the timer so I could automatically shut it off if left unattended. I never could get it to work. Eventually, I just took the USB end off the lighter and wired it into the timer. It is on when plugged in and off when unplugged. I use a USB power supply I picked up at VMWorld to keep the whole thing mobile. I use it at work, so this project was ultimately a success.