I have seen several guys make battery packs in waterproof cases to run led's and things of that nature with. I just want to know how. Preferably step by step. I am putting led's in my gear locker on my kayak trailer and want to run it off of AA batteries if at all possible.

You mean like this ~~>

With that battery pack I have put about 15 hours of usage on the first set of 8 AA batteries. I use a Humminbird PiranhaMax 170. If you use a FF w/ color or gps or dsi you'll battery life will be significantly less.

True. I had this setup with the same FF and got comparable results regarding battery life. I actually went all summer and fall last year, fishing an average of twice a week on 2 sets of batteries. Recently switched to a Mark 4 DSI with GPS, DI, and a display that requires backlight at all times and I get about 1 trip on the water per set of batteries. Switching to a deer feeder type of battery.

BC, if you are just wanting lighting in your gear locker, I use these in the campers of both my trucks with good success. Keeps me from using up the truck battery if left on at extended time, have kept working even with extreme temps in camper. Some are magnetic mount and I have used them in my truck with a metal topper and they hold well under travel. In my truck with fiberglass shell, I just add Velcro to the back of the light and stick it to the carpet. I have yet to change batteries after a years worth of use and it's nice to be able to grab one and use it like a flashlight when needed.

http://www.lowes.com/pd_163154-3-72435_0__