i bought an HID kit(plug and play) online. But after some research i decided to play it safe and bought a relay harness.
My question is some websites says to connect the harness to the positive AND negative of the battery. Some says connect to positive and connect to ground. Which one is it really??? or should I say which one is safer/preferred???

EDIT: Got the ans. Thanks for those who replied. But if anyone else out there is wondering: Ground=Negative

 

the negative of the battery is ground...

and so is the chassis... (which is connected to the negative of the battery)

 

where do you put the fuse at on the relay harness? sorry im a noob to HIDs.

 

anyone know how to install a relay harness for H11? im trying to install this kit on my friends 09 tC but i dont know where to put those two little ground looking wires (if thats what they are) that look like little needles. i know how to connect everything else just except those.