Verified answer

at home we always run ours on the AC adaptor. It is only when we go somewhere do we ever take it off the AC adaptor. We have the same charge time/run time as when we first bought it (about a year ago)

There is a diode that prevents over-charging of the battery.

certainly, what my brother does each and all of the time is he plugs in the charger of the pc into its superb port and only plugs it into the opening. From there he makes use of it w/out the battery.