HID bulb voltage question

I have a set of KC HID flood lights that are supposed to be 24v. I hooked them up just now and they didn't come on. I pulled the relay and replaced it with a 12v relay and they powered up. My question. Is their a difference in a 12v and 24v HID bulb? I have searched and found nothing. All the bulbs that I found can be used on a 12v or 24v system. Just my guess but correct me if i am wrong. The bulbs get watts from the ballast not voltage, i.e 35w or 55w. My ballast are 9v-32v. I can throw 32 volts at them and the light output wont change. Will They? I included a few pics of the light output they gave off. Its ok you can laugh at my make shift mounting but I needed to try and get them up off the ground and I don't have a place to mount them on the truck. I could have adjusted them better but they look to me like they are giving out the correct output. Sorry crappy cell phone pics.