hi sue try this xx
1. Plug-in your dead N7 to a wall charger. (Jump immediately to step 2.)
2. Immediately after plugging it in, press Volume Down and Power at the same time.
*This should get you into the bootloader menu. You may have to try this with different chargers or test out the timing in order to get it to work.
3. Once in the bootloader menu, use Volume Down until you see "Power Off Device."
4. Choose that option with the Power button.
5. Once your device is off, unplug the charger and then plug it back into the device.
6. You should now see the battery meter with your device returning to life