I want to run 12v to the bed for future bed lighting and cooler plugin. I plan to run a 12 gauge wire with a 10 amp fuse directly from the battery for the positive.
What about the ground? It is ok If I just take my ground somewhere on the back on the main frame?

 

Yeah, recommended. Shorter wire the better. Think of all the other wires in your truck, all (or majority) grounded to the frame (directly or indirectly).

 

Drop the spare tire. Look up, you'll see a ground you can connect to.

 

I think in the bed I would either switch power or use a relay. That way you can kill it if needed. I understand you want to power a cooler or what ever but straight battery voltage/ current (10 amps is a lot) just sitting in a bed of a truck is asking for a problem.

 

Ok so how much you suggest?

 

You can use a switch in the cab to activate a relay that supplies the 12V to the bed when needed. You could use two different relays one for lights and one for the cooler.

If you just run the power from the battery then the lights would be on all the time, you will need a switch someplace for the lights at least.

 

I plan to have a switch in the bed for the lights and have power to a lighter outlet for the cooler all the time so if I stop for an hour or 2 the cooler still as is power.

For the rating I will check how much the lights and cooler demand and I will go with a fuse for that

 

It is not the fuse size that is the problem. It is like running a straight power line from the battery and let it just sit open to anyone to touch. I know it will be in a plug, but that plug is open the the weather etc, even with a bed covered.

A relay is pretty easy to run and the switch in the cab allows you to control the lights and plug when you need them and turn them off when not in use.

 

Ok I understand but what is the difference of having a 12v outlet live in the bed or in the cab?

 

In the cab you have to work really hard to hit it with luggage coolers dogs cats and anything else you toss in the bed of your truck.