Stator coils are not the most common culprit in the charging system. The two most common gremlins in the charging system are a faulty battery (common with Lead Acid batteries) or a bad regulator/rectifier. See if this video below doesn't answer some of your questions.
There is always a chance you have a bad battery and that your stator is fine. The best way to test your charging system would be to fully charge your battery and measure the voltage. Put it in the bike and get it running, and measure the voltage as the bike is running. If it keeps going down well below 12-13v, around 11v and lower, it's the charging system not performing. If it stays fairly constant while it runs your battery might be faulty.
Similarly, if you fully charge the battery and let it just sit for a few days and the voltage drops considerably, then you should replace the battery.
If you have recently replaced your regulator/rectifier with a known working unit and your charging system is still not performing properly here's how you test your stator. Test the stator by checking the VAC while the motorcycle is running. Measure the VAC from white to pink and yellow to pink with your multimeter. This tests both halves of the output of the stator. If you get values around 15vac - 20vac from each side your stator is good. If you are reading around 5vac or lower on one or both halves, it's time to look for a new used one.