why does my battery lights keep coming on?

[ECLIPSEGST25]

ok on cold starts or if i haven't driven the car for like an hour or so the car is ok. but after a few start ups the battery light comoes on. some times it comes on and the volts are really low. but usually after a few minutes of driving the volt go up to like 13.7 and the battery light goes away and the car drives fine. i figure if my alternator was bad the light would stay on. what could be causing this?

 

[95blackGsTurbo]

Bad cell in the battery. Low crank voltage and then the battery is to low to take a charge. Get the battery CCA tested. Easy thing to do it test the voltage during startup.