G'day, Mate. I don't have the Blue Sea version, but have you similiar relays to combine the batteries. There are times, despite the different battery voltages that I want to have them combined and like the ability to do this manually. For example, I can run my fridge/freezer using an inverter
on the house bank. The wind
dies, we end up motoring and I can then combine the batteries to put the engine alternator
amps into the hosue bank. The house bank voltage is usually below 12.3 volts during this operation and the automatic relays usually prevent them from combining. Cheers.