Battery Charging Problems

by Fritz

I have a Powertap 55amp power supply and a Smart Charge Manager charging a pair of Lifeline 8D batteries (510 amp hours ttl) in a single bank. I use a Honda 2000 watt inverter generator to run the charger. It is a boat installation and during the summer there are two other charging sources, a 60 hp outboard and 240 watts of solar panels. Neither the outboard or the solar panels contribute much now but we are living on the boat in Alaska.

I am trying to decide if my batteries are bad or the charging system is defective. I know it is probably the batteries. The charger goes through the regular phases, brings the batteries up to 14.7 volts, bulk charge, absorption, float so seems to be working normally. After charging I tested my batteries individually with a 100 amp load type battery tester. They both tested very good. The charger is set at the Concord AGM setting.

After the charger goes into float I shut down the generator and after the batteries set for a couple hours the open circuit voltage is only 12.5. Lifeline says a fully charged battery should be 12.8 volts. A typical scenario then is after around 180 amp hours removed from the bank the batteries are down to around 11.8 volts open circuit voltage. I have a Xantrex Link 10 meter.

I would appreciate any advice or information/insight you might have