I've seen a number of videos on YouTube where people have built a "Power Box" by putting a 12V deep cycle battery in some kind of weatherproof box with a charging equipment and added various switches and ports on the outside.
I'm looking into building one of these for my annual camping trip in the desert, and was considering using this for a battery:
Mighty Max Battery 12V 22AH SLA Battery
Volume: 7.13" x 3.01" x 6.57" = 141 in^3
Energy Density: 22 AH / 141 in^3 = 0.15 AH/in^3
Weight: 13.1 lb
However, I also already own a number of Anker PowerCore Li-Ion based USB power packs like this. Which have nearly the same AH rating.
Portable Charger Anker PowerCore 20100mAh
Volume: 6.5" x 2.3" x 0.9" = 13.5 in^3
Energy Density: 20.1 AH / 13.5 in^3 = 1.49 AH/in^3
Weight: 12.56 oz = 0.785 lb
Both of these batteries are about the same price and hold about the same number of AH. Yet the USB battery pack is significantly smaller, lighter, and more energy dense.
If I don't have any need for 12V power, and only need 5V/USB power to charge my camera, cell phone, and run some LED lights. Is there any point to even considering using a 12V SLA battery?