What is a Reasonable Battery Voltage?
Our batteries lose their voltage quickly when we are at rest. We should have a 600 AHrs bank, after draining 100 AHrs the voltage drops to less than 12v. Should I be worried about their health?
From your description your batteries need to be replaced. At 50% discharge (ie. 300 AHrs) your batteries should have 12.2 Volts.