I rush-produced a video of this, which may be more interesting than reading for some people: https://youtu.be/G31ICABzKhw
But, if you'd rather read, here's the skinny:
I inherited these batteries from the previous owner, so I don't know how well they've been cared for.
After getting my solar charging system working, I started doing some experimenting ... the solar seemed to be working fine, but I'm concerned by how the batteries are behaving.
After fully charging till the Victron goes to float, I turn off all charging and monitor the battery voltage over the course of about two hours. During this time, the only thing using the batteries is the refrigerator compressor, which pulls about 4.5 amps and runs about 30% of the time. A little math tells me that over 2 hours the fridge should draw less than 5 amp-hours.
After two hours the battery voltage is down to about 12.5v. These are flooded batteries, and from what I've found on the internet, 12.4v is about 75% ... so, I'm guessing they're down to about 85% or so.
But for 5 AH to be 85% I'd need to have a battery bank with only 35AH. This bank should have about 330 AH.
Did I do the math wrong somewhere? Or are these batteries just really wore out?