So I have a small utility trailer that came stock just running a 4 way flat connector for the lights. I am putting in a 2 way flat to supply power to the interior. I am going the positive to the battery so that what i run in the trailer can be used when the vehicle is not running. So i have a few questions.

Distance from the front to the trailer where the loads will be located is going to be about 15 or so feet, maybe a bit more.

Gauge on my connector is 16, so the wire i have to run is 16 gauge as well.

From what I have read should be a max load of around 13-14 amps or so for this distance and gauge.

My questions are, do you think the 13-14 amps is correct, and will it be enough?. I am running an interior light (should draw only what, maybe 1 amp if that), I will also be installing a 3 plug 12v outlet to power auxillary things, biggest power drawers I have are under 10 amps for one, and the other would max at 14 amps, and max continuous at about 13, this is a power inverter, dont know how often i would run it, but guess it depends on how high the power demand is for what i have plugged into it. Later down the road i might install a cheapo car stereo.
Do you think this would be enough for what im doing now, 90 percent of the time will be just using the interior light and a <10amp drawing 12v accessory....or should I look at putting in a larger wire?

Should I run the negative to bumper or to the battery?

And where should i locate the fuse? in the trailer, or near the battery? Given the length and wire gauge would a 15a fuse be sufficient? If I run say 14.5 amps and with the length of the wire i should only be doing 14 am i going to end up melting a wire? or am i just going to see a power drop?

 

I wouldn't try running the power in the trailer off of the truck when it isn't running. That's a good way to end up with a dead battery.

What I would suggest is that you install a deep cycle battery on the trailer for the lighting/power inside, then run the aux power from the truck trailer plug to an ignition switched source so that the truck will charge the trailer battery when the engine is running.

 

^ i have a rundown protector on the battery in the blazer so if the voltage drops to much it will just cut the power. For what im using it for now is just an interior light and a small water pump -http://forums.mtbr.com/showthread.php?t=190931
the pump will only be run when i have the vehicle running. Its just inside a small utility trailer so i dont imagine to be using anything for a prolonged period of time.

Using the trailer to go to cycling races, if i end up using lots of power, or adding in a small stereo which i dont think would happen until next year (need to gauge this year how much time will spend in and around the trailer), then i would install a battery in the trailer, but not going to do that for the main sole purpose of running a light on the interior. For the power inverter the only thing i can even think i would be using it for now is to charge a cell phone, which i have run off the plugs in the blazer that are hot at all times. If the voltage drops the inverter shuts off anyways as well.

 

I did this very same thing and ran a separte battery (lawn mower worked for me and isolated the trailer inside electrical from the vehicle) That way I could dump the trailer and still have lights. If you're running a bunch of stuff then a bigger battery would be better. I just threw a trickle charger on it for a while when I got home.I was going to set it up with a diode so I could charge the battery driving down the road but just never did. There's all kinds of ways you can set this up.

 

I think im going to focus on what im going to use it for now, and if my needs change later i will switch it up.

What im going to do :
have 16g wire running from the trailer connector (flat 2), to the interior of the trailer, 15 feet maybe ish. For some reason i thought 25 feet of wire was going to cover me from the battery to the bumper, and from the trailer to the interior, apparently i was wrong, which threw off my amperage calculations as well. So 16g in the trailer, I am also putting the whole circut on a switch so i can cut the power to everything on this circut. Powering a single bulb interior light and a 12v outlet that will most likely just be used for that pressure washer. Was thinking about putting a car stereo in but not going to do that until i get an idea on how much i would actually use it....99% of the time i will be using the light it will be hooked up to the blazer, will put a battery powered light in as backup.

The blazer:
Running 12g from the battery + to the bumper on a 15amp fuse by the battery. Will ground under the bumper.

The future:
If my plans/needs change i will get a deep cycle battery on the trailer, have it charge of the aux on the blazer as well as a small solar panel charger, install a fuse panel in the trailer as well as thicker gauge wires.

 

Sounds like a good plan.