It was really more of a two part question, and that really helps. I was originally thinking small sealed lead acid battery. But… I’ve got a brand new DeWalt battery pack here for a drill, that the casing got busted on. I’m thinking of liberating the 18650 cells and repurposing them. 3.7v times 4 cells gives me a 14.8 volt battery.
I’ve not set up these types of cells before, and I’m still deciding on whether I need a charging / control circuit or not.
Learning new things is fun. 
