sounds like your alternator or something along the lines of your charging system...reason being, when you first turn on HIDs they draw ALOT more power than regular halogen bulbs to get it going but once they're on they use less power than halogen bulbs...first culprit i would look at the alternator get it tested, secondly you can have a bad ground connection or corroded cables somewhere...i'd definitely get that alternator tested first, it is free to test at most stores
