Hello, I am new here. I have a 2017 Express S4 and want to install a 12v cigarette adapter. The cart is 48v, there is a DC to DC convertor and from that, I see the fuse block. I plan on using an empty slot on the fuse box with a 10amp fuse, I'm runnin the positive lead to that fuse connection. Where should I connect the ground wire? Is the best place to connect the negative post of the last battery in the series? I don't think I should ground to the chassis . Thanks!