The initial charge is really long : ~10h through USB, ~6h using a mural charger.
Open up the diags, go to the battery check (where you saw "100%") dans pull out the cable, push it in back, then wait.
The voltage should raise during the 2 first hours.
If this doesn't work, then the only solution is to buy another battery or, if you can, return it to Texas Instruments.