If the mifi completely dies and has 0 charge, it can go into a "deep sleep". Even if the user plugs in the mifi, they will not be able to turn mifi on (screen will show unit is charging. Even if user has plugged in the unit for while).
If user wants to use glass and mifi sooner, have them:
1. Unplug power to mifi after about 5 mins of charging (this should give around 10-18% battery to mifi)
2. Now turn on mifi (now that mifi is no longer charging, the power button awakens unit and the mifi can turn on, bypassing the charging screen)
3. User can then connect glass to mifi and make a call
4. User can plug power back into mifi to continue charging