I'm working on a prototype for a project that needs to drive a stepper motor at 12V and 2A. It needs to be powered by lipo batteries, have all of the charging circuitry in the device, charge through a DC jack, and everything needs to fit in a fairly small space. I've been doing a lot of research, but I'm a bit of an EE noob. Originally I was thinking I would have 3 3.7v lipo cells, but after tons of research, I can't find any off the shelf board to do balance charging of a 3S pack.
It appears there are lots of cheap single cell charger boards. Does it make more since to just use a large cell (8000mah), and then use a boost converter to get to 12V/2A? The problem I ran into there is that it looks like most of the boost converters I found don't go up to 2A when going from 3.7 to 12v. (The efficiency loss is another concern, though for the prototype, I will take simplicity and a larger battery over complexity)
I'm sort of out of ideas at this point. I'm looking for something I can use off the shelf. Preferably something that costs under $30. Does anyone have any ideas on the best approach here?
Update: just to clarify. Ideally I would like the batteries to be self contained inside of the device and not need to be changed out. (The actual amount of time the device gets used will be very minimal, so battery life expectancy is not a big concern)