I want to make a li-ion battery pack, to create a 12v 10A power source, with a PCB to control charging and discharge of the batteries. I intend to charge the batteries while still in the device, with a 12v DC external power source if possible. I am using eight 3.7v 18650 batteries, with two battery packs of 4 batteries each. The two battery packs will be running in parellel, but the batteries in each pack will run in series. This makes 14.8v, which when fully charged would be about 16.8v. What is the best way to transform input (charging) voltage from 12v to the necessary ~17v, and then to transform the output voltage from the batteries down to 12v, for use for my 12v device? Can anyone help me? I hope this makes sense, please ask if you need more information.