All it takes is a momentary power glitch for the Traeger to shutdown. This may not be an issue if you are continuously monitoring your cook, but if you are doing an overnight cook this occurrence can ruin your expensive cut of meat. You could use a UPS device, but they are not ruggedized for outdoor use. The Jackery is perfect for this. The 300W Jackery will easily power a 24 hour cook. This is the best price I have seen for this.
Jackery 300 Portable Power Station