Neil said that there were at least 3 people interested in the battery systems that I built. So, here are the pictures and the details.
I bought at Costco the 115amp deep cycle batteries.
One of the hardest things was to find a cooler with the proper size for the battery. The benefit of a cooler is that if the battery spills, the fluid will stay inside, the vapors will have a harder time going out, and for transportation, it is easier to stack stuff on top of the batteries. I found these cooler for $14 at Walmar (after a lot of trips to a lot of place). The handles are a bit flimsy but they seem to hold up OK. These coolers are 28 quarts coolers. They are very easy to cut with a working knife.
I got an external 12V switch. Initially, I bought it at Radioshack but I found them to have a very loosy/goosy contacts and they could easily failed in the middle of a exposure. So, I visited Parkrose Hardware and I bough the solid ones you see in the picture. I don't remember the price but they were a few dollars.
The cigarette lighter adapter is from Fry's Electronics, I cut the ends, and I use some wire joints so I could tie them to the switch and the battery. I believe the cigarette adapters were a few dollars too, nothing expensive but I found the quality from the Fry's Electronic ones to be superior than the ones from Harbor Freight.
The battery voltage indicator is from Harbor Freight. It was unexpensive too, I believe it was around $6.
I used a drill to make an initial hole, and then a cutting working knife to make the holes to a specific size. They were easy to cut a brand new blade.
I made the holes tight and I used superglue for added strength.
One battery system is for the laptop and the other one for the mount, cameras, etc.