If the alternator is charging the battery, but the battery is weak every time you come back to start up your car then it could be something is draining out the battery.
It could be an interior light you forgot to turned off. Light in the trunk, or shorted wires.
You can use an electrical multimeter to do what is called "parasitic draw test" to know for sure.
The car batteries need to be fully charged all the time. If you leave them not fully charged for a night or two, changes you will need to replace your battery.
Possibly a dead cell in the battery. Old battery cables or connectors. Did you have the alternator tested? Did they check for a blown fusible link between the battery and alternator?
Your battery is dying. New battery needed.
Get your battery tested. And if the new battery you might get, does the same thing, get the parasitic draw of your electrical system analyzed. Shouldn't be more than .33 amps.
It is not the alternator. I have to charge my battery and then put it on the car after every hour trip I make! Maybe something shorting out the battery?
