Battery won't charge

you need a multi tester to see if there's 14+ volts when it's running , or if the batt has 12.5 when off , You may have a short draining it , pull the cable when you park it see if that helps

To expand on the previous answer, if you had a multimeter that was the "clamp" style and it could measure DC amps, clamp that around your battery cable and see how much current is being used. It should be minimal. You could have something like a light in the glove compartment that is staying on or some other situation drawing power. Like the previous answer mentioned, if you don't measure a slightly higher voltage on your battery while it is running as opposed to when it is off, your alternator may be bad so it cannot charge your battery.