Hello Scott, I realize your posting was from awhile ago, but I am getting ready to convert my Amel 54 (Phantom) to LifePO4 batteries. I have read your "dissertation" with great interest and am interested in getting an update from you before I make the plunge.
Have you been able to resolve all of the "problems" you noted? By the way, here is what I am planning to install with my electrical contractor:
(12) 24-Volt (50 AH) Battle Born LIFePo4 Batteries
(2) Victron Multiplus 24/3000/70-16
(2) Victron Smart BT Dongle
(1) MK3-USB Adapter
(1) Mastervolt Alpha III Regulator
(1) Victron BMV-712 Smart Meter w/Temp Sensor
Since I already have a 3kVA inverter, I did not want to upgrade to a Quattro or a higher capacity Muliplus unit. That would have forced me to do a lot of wire upgrades, and I think 3kVA will suit my needs. With the lithiums, however, I have decided to split my AC bus into 2 columns - 1 side for inverter-capable and the other for high-current loads, such as my 230V(only) watermaker, dive compressor, and saloon AC. We decided on 2 inverter/chargers for redundancy, where one unit will be set up for charge only. That way I can charge and invert simultaneously, and even provide 50hz power when connected to 60hz shore power in the US. I intend to use the existing battery charger circuits to feed the Multiplus units, so as to maintain the flexibility Amel provided originally. The incoming shore/generator ATS will remain as is.
I also have at least one possible solution for you regarding some of the "problems" you indicated you still had to resolve. Maybe you have already found the solution, but I have used the following Elk Products relay very successfully, and I'll bet it will work for your Mastervolt reg disconnect. This is what I intend to use.
ELK-924The ELK-924 Sensitive Relay module features DPDT (Form "C") dry contacts for general purpose switching of devices or high current loads. It operates on 12 or 24 volts DC and can be triggered with a negative or positive input at an incredible low current of only 1 milliamp. Also available in a 4 pack (ELK-9244) which is packaged as 4 relay modules grouped on a pre-scored break-off circuit board.
Hope all is well with you.
Phantom A54 #44