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 this would be to fully charge your battery, 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 it's the charging system not performing. If it stays fairly constant while it runs your battery might be faulty, which is not uncommon.
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.