Im curious why

Hi there. I saw your original post but had no particular advice to offer, so I didn't bother. However, I hate to see you neglected so here's my opinion.

I can see no reason why you can't run your Cyclone II system from rechargeable batteries. Depending on the device you use, I can imagine that the current drain could be pretty high. I am just about to get my first Cyclone II based prototype board back from the manufacturers and so I'm still feeling my way a bit with the power requirements.

In order to derive the necessary core, PLL and I/O supply voltages from your battery I'd look at using a multi-output switched mode controller. A rep. from Arrow showed me a little evaluation board the other day for a Linear Technology device which occupied a very small board area and needed only tiny external components. I'm sure National Semi etc. will do similar devices.

One other thought. If you haven't started your design yet, should you be looking at Cyclone III instead? Maybe others could comment.