In short, my battery bank no longer lasts more than 20 seconds when it used to last days.
So, this past summer I bought new batteries (Trojan L60 x 4) to run my home. I was replacing sealed batteries which still worked, but not as well as they used to. I taught my wife the maintenance procedures, but I neglected to tell her how important it was, especially for the first few months. So, she went ~4 months without ever checking the batteries with the hydrometer. At this point, the batteries only lasted for about an hour before they needed to be charged again. Initially, one charge lasted 3 days as long as she didn't vacuum or run the big desktop computer. I spent a whole weekend running an equalization charge and while the ph levels improved, they never fully equalized. After this, the battery life did not improve.
Since then, I have only tried one thing for troubleshooting. I hooked up the old batteries (that worked before the 'upgrade') and they also would not hold a charge.
To me, that tells me that the batteries aren't the main issue. Yes, it was bad that we let the batteries go 4 months without maintenance, but something is wrong with either the inverter or charger, or that there's a wiring issue somewhere.
I'm not at home right now, so I can't answer specific questions or provide pictures, but the great thing about forums is that I don't have to be immediate.
Do any of you amateur/professional electricians know where I should start with troubleshooting?