Time to get or use a cheap digital meter. For all you know the battery charger may not be charging. A quick check is to turn on your headlights and see if they are as bright as usual.

The starter or a connection may have let go as well. Without a meter though you are probably just guessing what is wrong. A charged up battery in fairly good shape should have a resting voltage of 12.5 volts several hours after the finish of charging.