That doesn't sound too good. :p
If I were to use D cells, I would use 5 of them (1.5V * 5 = 7.5V). If I do this, is that in danger of blowing up?
On an unrelated note, what you said reminded me of my "hand warmers" I used to make. They were just two 9Vs hooked up to each other. I was so...