Auxiliary Power Supply For Pellet Stove

Is there an alternative power source available to keep my pellet stove running during power outages??
I currently have the largest converter I could find hooked up to a deep cycle marine battery, but I have to unplug the stove from the wall outlet and then into the converter when the power goes out. Needless to say that doesn’t work too well when no one is home. It only lasts about 40 minutes using the largest battery I could find.
I would like to find something that “kicks on” automatically when the power goes out and will run longer than 40 minutes.
Any suggestions?
Thanks,

Only thing I can think of is a an automatic generator. Big bucks though...

Harman makes one for their units, reputed to run for up to 8 hours, but I'd say its more like 6hrs.....pretty expensive tho, around $400, without the battery.

The vendor I bought my stove from, recommends and sells the Surefire Stove Sentry, which sounds like it will do what you want.

http://www.secamerica.com/ss_sentry.html