My battery remains at 100% even after several days

This is because, we have reserved some capacity of the battery to support many months of "shelf life" (in the case of the TT-7100 the shelf life is 12 months). In other words, if you use the device after 12 months, will get the expected battery life and the % will start depleting immediately. However, if you use the device before the shelf life "reserve" is used, the battery will show 100% until the actual battery voltage reaches the shelf life reserve threshold. This is why in this case, you are seeing the 100% for a few days.