Start the Engine and measure the battery voltage.
If it is above 13.8v, (~14.5 typically), the charging system is fine.
If it is below 12.6v, you have a problem, and if it still starts the engine, don't leave the dock because it will be dead soon.
If the Voltage is above 14v with the engine running, shut it down and wait a few days.
If after a few days the battery measures less than 12.5v, the battery is weak or something is draining the battery.
If you still have at least 12.5v after a few days, Pull the safety lanyard to prevent the engine from starting, and then crank the starter for 20-30 seconds. If it is still cranking after 20-30 seconds, the battery is Good!