Yes you can use a 12Vdc power supply. Think in terms of total watts. Watts= Volts X Amps If your volts are low your power supply will need to provide more amps to keep the watts constant. Does this make sense?

A good 30A power supply is going to cost you. I just bought a 40A to power 2 Hyperion EOS0610i's and one Hyperion EOS1210i. I went with a [link=http://www.mfjenterprises.com/Product.php?productid=MFJ-4245MV]MFJ 4245[/link] adjustable voltage switching power supply. You can see a pic of my charging setup in my gallery. I have been very happy with this setup. I can easly charge three 6S 2500 lipos without it even breaking a sweat. I got the large 40A version becuase I am thinking of possibly building a T-Rex 600 in the future and would like to be able to charge 3 6s 5000mah packs.

You might also check out the Pyramid line of power supplys. They are more inexpensive than the MFJ I have. They are also a linear power supply and a 30A version is going to weigh in at around 35lbs or so. My 40A switching power supply only weighs 5.5lbs.

Good luck!