If your ego batteries fry your computer, you needed a new computer anyway imho.
Most computers will have no issue with charging an ego battery while it's being used, as the power you are drawing is from the battery. When you are using it is coming from the battery not the USB port. "Ego Passthru's" are not actually passthru's. If they were I would have blown my front usb's months ago with a dual coil on my ego, pulling 4.4 amps. USB 1.0 supplies a max of 100ma, so yeah that would have went boom awhile ago.