I use one of these which hit 8.39v or 8.4v on the brca volt meter at the f3,4,5's every time.
http://www.dms-racing.com/index.php?...ategory_id=528
you can also buy a power
http://www.dms-racing.com/index.php?...ategory_id=175
if you want to run it off the mains.
I run mine straight off 12v and it seems very efficient on power consumption