Electrical power is produced by the bike's alternator which has a stator (some magnets arranged with coils of wires around it). The electric produced however is AC (Alternating Current).
To charge the battery, this AC is converted to DC (Direct Current) by the rectifier or regulator.
A fully charged battery should show 12.6 DC Volts.
The alternator (charging system) will charge the battery whenever the DC generated is above the battery voltage.
IMHO, the alternator only maintains the battery health.
To fully charge the battery, it's better to get a float charger (like Optimate 4 and others out there).
Would recommend a digital voltmeter onboard the V to see all is good with the alternator. Without starting the bike, you can see the battery state. When the engine's running, the voltmeter (14.0-15V) will show the charging state.
With the bike running, any charging voltage below 14V and more than 15V will tell something is wrong with the rectifier/regulator.