Small Engines (Lawn Mowers, etc.): John Deere 116h charging, circumfrence, alternator output

Question
I have a John Deere 116h, the battery and terminals are new, I just can't seem to keep the battery charged.  If I fully charge the battery with a charger it will be fine for about 3-4 mowings.  After that I need to re-charge the battery, what do I do..check?!

Answer
To test the alternator output, or the diode, you would need a
multimeter, but with a simple voltmeter, you can see if the charging system is putting anything out, but it sounds like it isn't.
Just read the battery voltage with the engine off, and then test it again with the engine running.
The alternator is under the flywheel, energized by magnets glued to the inside circumfrence of the flywheel, and looking at your mower
at JDpartsonline, you have one wire coming off of alternator, with a rectifying diode.
  So if you can get your hands on a multimeter, I can take a pic
of the page of the manual for the test procedures.