Check voltage of each cell. They should be similar. During charging they should reach absorption voltage and remain there a couple hours, then drop to float voltage. Exact voltage is computed based on temperature.
Use a hygrometer. That gives specific gravity.
Check settings in Midnight and compare to GNB specs. Does the trailer have a shunt to inform Sunny Island about battery current?
Or, does it have a data cable and interface board between Sunny Island and Midnight so Sunny Island controls?
If using an AC source (Sunny Boy, generator), Sunny Island would control that.
Check settings and adjust if needed for both Midnight and Sunny Island.
I expect maximum charge current to default to an excessive value (0.55C) which wouldn't matter unless you added lots of AC coupled PV like I did.
If some cells are lower voltage than others, I would get a bench supply with constant voltage and constant current. That would put in constant current (say 10A) until absorption voltage then sit there. Monitor it and after appropriate absorption time, disconnect and move to the next.
Ideally this would occur while other cells were fully charged, so this one doesn't get ahead of others.
I have a "DAS", bench meter with relay cards. I would consider that plus a power supply for an automated BMS/balancer. But just going through occasionally with a bench supply should be good. Some people suggest equalization is hard on the cells that get overcharged, so I figure individual charging would be better.
Why disassemble anything? You could leave all as is, but add a large quantity of panels on a Sunny Boy. Up to about 24 kW of Sunny Boy.
But I guess having it on a trailer isn't helping if you don't need mobile, and you could free up the trailer.
DC Solar's box doesn't provide proper space for convection cooling. Read up on that before making your setup.
The tilt-mount could be convenient. Maybe you could double the number of panels per tilt. Orient one tilt SW, one SE, and their combined output will have lower peak. More watts would fit the charge controller. Your rooftop panels may all be a single fixed orientation, so using these racks for tilt-able and catching sun other hours could improve the system.
Batteries outgas and are corrosive, so should be walled off and vented. But they would prefer more controlled temperature.
