Simply put, you need to check the voltage that the alternator is charging. Install your meter (or borrow one) on the battery and see if you have about 14.+ volts at about 2500-3000 rpm.You need this much voltage to have a decent amount of amps going to the battery. Next simplest item would to see if you have a draw on the battery. Next you should take the battery to a scooter or motorcycle repair shop and have them do a brake down test on the battery to see if it has the capacity to hold a charge. Let us know so we all can help. Howard