Chuck,

You have a 24V house battery bank. Featherlight wired half of the batteries to their negative and 12V bussbars. The other half are wired to the same 12V bussbar and the 24V bussbar. An equalizer sits on all 3 bussbars. It's purpose is to pull current from the upper half of the bank's batteries and send it to lower half bank based on the 12V loads.

If you want to measure the banks SoC you'll likely have to add a negative bussbar. You'll install the SoC shunt between the negative bussbars. One negative bussbar will only be connected to the batteries. The other negative buss bar will connect to each inverter, chassis, and anything else on the current bussbar that's not a battery.