When connected to your computer for whatever purpose you need enough battery power in the camera to do the job. It would be handy if the display of ongoing USB connection on the LCD showed the battery power level so you could keep an eye on it, see the rate at which it was going down, etc.. Which I noticed it actually did now & then! But how could I make it do that?
Maybe I'm careless enough not to have noticed this in the manual. I discovered that if before connecting to USB you set up the LCD to the display type which includes battery power level, then the battery power level will be displayed on the USB connection display.