The electric clutch is magnetically controlled. Low voltage will cause the clutch to drop out. Turning off the mower and letting the battery rest will probably allow the clutch to engage again. You need to measure the outside terminals on your voltage regulator. My stator was destroyed due to a loose magnet under the magneto destroying the alternator mounted under it. I ordered a new magneto and voltage regulator and all is good again. Your symptoms are exactly as mine was. I have the 54" cut with a kohler engine. If you periodically have to charge your battery then you have a charging failure thus the PTO failure during a mow. Check your voltage before taking everything apart. If you have 18vdc on the two outside terminals of your regulator then the alternator is still putting out. Disconnect both outside terminals, then with engine running check the volts output. The center terminal is your output to battery. If you have and ohm meter you can check center to outside. Reverse leads measure. You should get nearly exact measurements from center to outside termials. If not replace the regulator. You might get lucky and it's only the regulator and not the alternator too.
