[ShinyC10]

Originally Posted by Axle

80 will hold you over for now. Your 40amp just wasn't enough.
Just don't turn everything on when you start the truck, and let it run for a minute or so to let the alternator just re-charge the battery after starting. The longer it sits between starting, the more important this is as the batteries need more charging and will take a significant draw.

Under ideal circumstances, you would be fused higher than 120. But you would also be running a heavier wire from the battery direct to the alternator output (fused).
Consider the 120 amp to fuse the 4 guage wire, and not be stressed by your load. I will say, don't let this get you all concerned at this point, unless you start really putting a serious load on the system. If you are mostly stock at this point you probably won't run into any issues. And with LED lighting, I'd go so far as to say if you do go crazy with adding flood lights, LED's are not going to put you in the danger zone like a couple sets of old incandescent lights would.

What you do want to do is get your hands on a clamp on DC ammeter so you can verify what kind of current the truck is drawing after a start. And what kind of current it is drawing when you have everything turned on. Both for peace of mind, and verifying something else is not wrong.

Alex.

Sounds good. Thanks for the help guys!