My battery is not getting hot anymore. I had the on/off switch wired wrong because I didn't understand how switches were wired inside(I told you, I'm new to this electronics stuff!) but I did a little research and got it right.
If the drain is supposed to be 1/2 of the voltage supply, would it not make sense that if my battery was worn down to, say, 7V then the drain should be adjusted to 3.5V?
Pete: Any chance of you givin' up a schematic of your circuit? I'd love to compare it to the fetzer-ruby using the same driver. Or maybe you can build a fetzer-ruby and try it with your driver so we can isolate which symptoms come from the driver and which come from the circuit.