It's been to the dealer twice now. They have not been able to figure out what drains the battery. They said they checked to be sure that when the mower is running, the correct voltage is being produced. Unfortunately, the problem manifests itself after the mower has been sitting for just under a week. Perhaps there really is a problem with the battery. If/when this happens again, I'm going to buy an Interstate battery and see if that solves the problem.
I bought this mower because I wanted to buy a US product. Now I have an unreliable product sitting in my garage. Next time, I'll go with Kubota.