I'd venture that you have one battery that's a cranking battery, and two that are wired in some combination as a house bank. I'd start by tracing your system, as you really do need to know where your power is coming from.
I'll also provide a dissenting opinion from the rest of the thread regarding the charger. I'm now using two Promariner Prosport 20HD chargers, one 2 bank, one 3. Both have been running great. They have a really good user interface with diagnostic LEDs and a "fuel gauge" style display that shows your charge level. They can also be configured for lead acid, Gel and AGM batteries. But what really drew me to them, is what they call the "distributed on-demand" feature. How this works: the charger is a 20A charger, charging let's say 2 batteries (2 bank). The charger will sense the charge level of each individual battery and dedicate its charging amperage accordingly. So say your starting battery, which just cranks the motor, is at 90% charge, while your house battery is at 60% charge each. The charger will take the total 20A capacity and dedicate more amperage to the lower charged battery, such as (ballpark) 7A to the start, and 13A to the house. This will charge your batteries faster and more evenly.
In contrast, most other multi bank chargers, including the NOCO I believe, divide their output amperage evenly by the number of output circuits. So, if you've got the same setup with a 20A charger and 2 batteries, both get 10A, regardless of battery charge state. In a well set up electrical system, your house batteries will likely always be more discharged than your start batteries. So the distributed system means a faster charge time.
But, to circle back, your first task is to start looking at batteries and cutting wire ties, to figure out exactly what's going where in your power system.
Have never seen one. I install NoCo Genesis chargers.
