so some searching here - tons of comments about these units...
Most will tell you to junk it and get a new 3-stage, solid state, converter/charger that will do a far better job of charging your batteries...
Many look to
BestConverter - Converters, Inverters, Electrical Supplies, Electronics for replacements - they have good prices and great service and will steer you in the right direction for the replacement best for you...I did, and am happy with what they recommended...