On an earlier trip this year I had a problem with my batteries not holding a charge overnight. At the time I was having trouble with my 12v fridge, this was changed for a new 240v fridge freezer unit. The batteries were all took of the boat once fully charged, left for a few days and then tested, they all showed 13v. One thing I did discover was a broken clamp on the battery bank which was replaced. Thinking that might have been the problem we planned to go out for an autumn cruise this week, the boat has been plugged in to shore power for the last two days to get the fridge freezer down to temperature. I disconnected the shore power at 1630 this afternoon and by 2130 this evening the inverter cut out because the voltage had dropped below 12v. I have a battery bank of 4 12v 110 amph batteries for leisure, sterling 2kw inverter, all led lighting, small 240v TV and a water pump. The inverter is over ten years old but not showing any alarms and works perfectly until the volts drop then it cuts out as it should. I'm at a bit of a loss to understand what's happening, has anyone got any ideas?