Congratulations. Best money ever spent. I have had mine for three years.
Here is a link to a thread all about inverters and batteries.
http://forum.cookshack.com/eve/forums?a=search&reqWords=battery+ I bought a 500 watt inverter from Sams for around $30.00. It can also be plugged into a cigarette lighter socket. A deep cell battery from Sams is about $45.00. I use a small battery charger. (1.5 amp per hour automatic charger) I have run on battery power for more than 20 hours. My unit has the early digital readout.