Backup Lights

When im doing all the mods to the rear of my zuk, (i just finished putting in my new tail/brake/turn lights on the tail gate) i want to put in some really bright backup lights. I picked up these badass tractor 'lamps' (looks a lot like an off-road light but in a rubber casing), and i want to mount them on the ends of my bumper.. I tried them out first using the battery as a power source then the little stock backup light wires. I didnt notice much difference in the brightness, and using the little stock wires, i held it there for about 30 seconds, they didnt get warm at all.. So does this mean i dont have to Use a relay? I really want to get these mounted