Short answer: No you dont need one
Long answer: I always use relay kits with HIDS that I install in any car. The relay will make sure the stock wiring does not overheat from to much current. There are relay kits available with the resistors the cancel the bulb warning signal as well. Here are the relay harness I used on the Crossfire
HID Fuse Gold Relay Harness Wire Chrysler H11 H7 9007 on eBay!