Two Lithium polymer batteries are connected back to back and in parallel to the regulator. The batteries are rated at 9.47w @ 3.75v each.

When you are satisfied that the battery is properly installed, the new battery should have enough charge that you will see at least one of several LED's light up. You can then close up. But if not, charge the unit via USB to see if the LED's are functioning. If not, check the battery connection.