Hi, my inverter is a few years old and worked perfectly up until a week ago. I find that the charger is not charging my batteries. When I turn the unit on at first the green inverter light comes on, but after a few seconds this goes out and the amber charge light comes along with a constant alarm light. I have fully charged the batteries using a separate charger and the batteries are good when I've tested them. Could someone point me in the right direction to solve this issue?