Anyway, I have quite a bit to learn in this area. I've worked with power, but its almost always been external / data center-scale power. Onboard power is less sexy but no less interesting and substantially more helpful to my own individual hacking efforts. This new-found interest has lead me in all sorts of directions. I've found myself Testing Laptop batteries instead of reflexively replacing them when they start acting funny. The video below has been quite helpful to me - testing the actual capacity of a laptop battery can be a bit complicated, and measuring the voltage of a battery requires you to run to ground (which in turn requires you to figure out which terminals the ground *is*). Check it out: