I need to power a security camera that won't have mains + adapter nearby.

the specs are: 9.0V/0.6A (DC Power)

So figure 3S to provide ~12V and lots of charge. 

I already have the camera, and an old e-bike battery so I thought I'd break down the big battery into the 18650s, and create a new small battery for use here. I'm familiar with DC electronics and lithium (lion & lipo) cells, though I've only built little things with cheap boards from AliExpress. For this project, I want a proper one that has under/overcharge protection and balance charging.