> it's just the right voltage to charge lithium ion batteries No, it's not. Lithium is nominally 3.7 volts per cell and charging voltage goes up to about 4.2 v

> it's just the right voltage to charge lithium ion batteries No, it's not. Lithium is nominally 3.7 volts per cell and charging voltage goes up to about 4.2 volts max, maybe 4.3. Definitely never 5V. A 5V->4.2V buck converter isn't particularly different than a 20V->4.2V buck converter. In fact it's probably a bit easier to make a 20V->4.2V converter since you don't have to worry about parasitic losses as much. > You do realize that this is exactly your pitch for these 20V "standardized" plugs/outlets, right? :) Not exactly, (a) I'd use an existing connector, maybe a Lenovo 20V connector (b) USB keeps having to switch things because they weren't a charging standard to begin with, they were abused as a power plug and then had to keep evolving with that while maintaining backward compatibility and continually keeping up with Moore's law in bandwidth requirements. A 20VDC plug would just be that -- a low-voltage socket for <100W appliances. Anything higher, just use 120V/240V and get upto 1800W.