i save important stuff. batterys, screens that sort of stuff.modern pcbs arent very easy to modify as they ate typically multilayerd and use components the size of a pinhead. not very tweakable often they dont survive dissassembly. it would be a million times easyer to make my own pcbs from scratch than to tweak a roboticly assembled one.
as for the battery, it has 3 wires coming out of it obviously one is voltage and the other is ground, the 3rd is probibly either a charge wire or a control signal. i still havent traced the model number down. 5 volt input could be converted to something else by the time it gets to the battery. when it comes down to components at this level its a good idea to read the electrical specs on it.