Does anyone know how to wire a 12 volt battery hook up on a gooseneck horse trailer to run interior lights with out having it hooked up to the truck and what parts I will need besides a battery and a tray.

You trailer's pigtail wiring usually is terminated on a terminal strip or junction box inside the nose, or under the goose area; somewhere near the front of your trailer.

If you run a power source from the positive (B+) battery terminal, to first a fuse or a circuit breaker and then to the wiring that supplies your interior circuit, you will be able to then directly power that circuit using the battery. The negative battery terminal should be wired directly to ground.

It is advisable to add a battery terminal, electrical disconnect switch, so that all power can be isolated from the trailer during storage. This can be found at most auto parts stores, and is commonly used on automobiles, that are routinely stored for lengthy periods of time.

You will also need Adell clamps, a suitable length of wiring of a 10ga or 12ga capacity, some tie wraps, perhaps a grommet or two if you penetrate the bulkhead, some heat shrink tape and appropriate wiring terminals applicable to each end of the wiring. Finding crimpers for that gauge wiring can be difficult, sometimes it's easier to use solder type terminals.

Gard

gard,   so i take a 10 ga. wire from the positive side of the battery to a fuse and then a disconnect sw. and then to the terminal block where the 12 volt light hook in to, and what size fuse should I use and what is an adell clamp,  thanks for your help Jim

The disconnect switches I use, mount directly onto the post of the battery. So they would be first in the circuit before the fuse. A circuit breaker is similarly priced to a fuse installation, if you consider the price of a rigidly mounted fuse block. It's advantage is not having to have spares, and it auto resets when the short is gone. A 20 amp fuse/breaker will work on a 10 ga wire.

Here's a link that shows what the Adel clamps are. The pictures are much better than my descriptions. They are used in aircraft construction, and because they are aluminum, they will not cause electrolysis when placed against the aluminum trailer's construction.

http://www.hi-line.com/wiremanagement-adblackaluminumadelclamps/182

Gard

will this charge the battery when the pigtail is plugged in to the truck and it is running or will I need a separate charger,  thanks for your help gard  

It would depend on how you wire the circuit. If you open the line from the truck and butt splice the new battery's B+ wire to the trailer wiring, you have created a dead loss system. The interior lights are now dependant solely on the battery. The battery will have to be charged with an auxiliary device.

If you add the B+ wire to the juncture of the truck source wire and the trailer load wire, you have created a parallel source. With the truck source off, you will draw from the battery. With the truck source available, you will draw from both. With the truck running, the truck source will charge the aux battery over a period of time.

You're welcome

Gard