Well, our new last year RadRovers were acting the same way.  We had the batteries for both bike off the bikes and stored in our basement.  I completely charged them at the end of last year.  Got them out today (I know, we are late at getting out on the bikes) and pressed the battery charge meter on the battery, and they were completely dead.  Put them on the charger, looked at them 15 minutes later and the chargers for both batteries show one red and one green led, fully chaged.  I checked the battery meter again, still dead.  I am thinking, "GREAT, my batteries are toast"!  I searched the forum and found this thread.  Checked the 5 amp fuse, it is fine.  Then, it occurred to me:  THE KEY HAS TO BE ON FOR THE BATTERY METER TO WORK!!  The batteries were still fully charged after being in storage.  I hope my story helps someone else.  I feel like an idiot.