My current project is a smart battery charger / maintainer. It started out as a charger for 6V 4.5A battery packs. Now that that one is built, tested and in use I've grown the design to 12V 6A for automotive use.
If I didn't have my existing design to work from, I might have started with the Strawberry Pi for logic and PWM pulses... Don't really need unix to charge a battery though.