I did a DC conversion a while back and it caused nothing but nightmares. I have an eletronics degree and know what I'm doing too! Got a 250watt stator from RMATV already wired for it, got a ricky stator 200watt unit and did the conversion on it. Had the voltage regulator and everything. I burned up 3 stators with that shit. I will never do it again. Get some good bulbs, a bigger stator and run them on the stock wiring harness. I've talked to 3 people who did the DC conversion and all of them said it would burn up a stator in a matter of weeks. Same thing happened to me. Lesson learned, money down the drain.
The only thing the battery really lets you do is run them full wattage even when the bike is off. Plus it will give you a little more power. The stator is then used to charge the battery when the bike runs.