I'm considering adding power control and regulation electronics to my bot. I'd like this it to be able to turn itself off, read its battery level, allow hotswapping of batteries, and handle recharging when an external power supply is connected. Is this something most people design from scratch, or are there any pre-designed boards you can buy? I've Googled for it, but have found nothing. You'd think with the plethora of boards out there for processing, sensors, and motor control, there would be something for a mundane task like power regulation.