I am upgrading the storage capacity of the 12v electrical system of my boat and seek some advice please. Generation is from the engine’s 115A smart alternator and 240v AC shore power 20A charger.
The engine starter and winch are connected to a single (aux) 70Ah lead acid battery and the boat systems to two (main) 70Ah lead acid in parallel. To ensure the main battery does not drain the aux on anchor I have isolated the two systems with a Victron Cyrix-ct 12/24 120A battery combiner. Main and Aux are monitored with a Victron BMV-702.
The two main batteries are fairly serviceable and do contribute so am reluctant to dispose of their capacity/contribution. However I plan to add two or possibly three AGM or Gel 100Ah batteries to the main bank.
Would wiring isolating the lead acid batteries and the AGM/Gel batteries with a Victron Orion-Tr 12/12-18A 1) make sense and work 2) protect and allow full charging of the AGM/Gel batteries?
Your comments and suggestions would be most welcome. Thanks,
Sanity check please... for simplicity I’ve decided to go with Phase 1 above. Basically the Orion-Tr and two AGM 12v 100Ah. Think my Cyrix-ct 120 is now redundant. 
