I have had my off-grid system now for 6 years (Victron Multi + AGM batteries). In that time I have observed that solar input charges the batteries far better than a generator (pure sine wave). Being 6 years old but well treated, I suspect my batteries are near end of useful life because after one or two days of non-existent sun, they fail to hold voltage throughout the night. This is despite the fact that I run my gene at the end of every (poor sunlight) day to get to 100% SOC. When I have good sun, the batteries always behave well. Is this a known behaviour of generators and is there a way to get more 'power' to the batteries even though SOC is 100%?
