Led light bar wiring problems

Hello,I am in need of some help. I have installed two led light bars and two wiring harnesses, one in the front and one in the back. I am wiring this up on a 48volt Bad Boy buggy with eight 6 volt batteries and going from one positive side of a battery to the third battery in line on the negative side which is giving me 12 volts. The wiring harness has the relay, fuse, switch and all connections on it. I wired it all up and the switch light will come on but the lights will not. I can take the same positive and negative wires and run to the 12 battery on my truck and everything works fine. Can somebody please tell me what is going on. Thanks

Do the lights have only a power wire, or is there a power and a ground wire? If it has only 1 wire you need to make sure the chassis of the light is mounted to the chassis of the cart. You will also need to make sure you are using the battery that is connected to the chassis of the cart and the battery just beyond that one for the power of both the switch and the lights.

Thanks for the replies. I figured it out last night. The previous owner had put a cable with red tape on the ground side and a cable with black tape on the positive side so I was hooking it up backwards. Thanks again