Initially it was 4+ hours. We've been finding it has more battery life than 4 hours, but it seems to be dependant on the environment (ie, leaving out in open air vs a smoker vs an oven with a front glass door, etc. We have had it run as long as 10 hours in open air. This weekend it was 7 hours in our heavily insulated smoker at around 250. Will you run a test after charging for a full 10 minutes in open air and let us know your results? Start a session so you can track it.