I have recently purchased 2 used Audiovox VBP500 systems from 2 different sources, plus a new battery from a 3rd source. Out of the 2 players and 3 batteries, none will charge a battery or hold a charge. Both players will indicate charging with a red light on the unit, which will stay on for only about 5-10 minutes. I charged all 3 batteries overnight on both units, and no battery will play for more than 15 minutes in either unit. Both players work fine on AC and DC car power, but not on battery. Anyone else had this problem with these or other Audiovox batteries/players?