1) Keep lead acid for bow thruster. Its there, wired and working... no real advantage to making any changes. 2) The ACR is fine for that, between the start battery and thruster battery. Really you are just topping off your start battery and bow thruster battery. They shouldn't be drained all that much. 3) 30 amp Orion is fine.
The Bow Thruster Battery Bank is a lead acid 904D 1050CCA installed in 2015. The Bow Thruster (Lewmar 140TT 3hp) is Rarely maybe once a week and when it is used it’s for less than 30 seconds or a minute at most. The Bow Truster is a Lewmar 140TT 3hp 12V motor rated 280 Amps on the cable size diagram. 3.
1. Best to keep the FLA for the bow thruster and maintain charge through the house bank. As Mr. Sandals said LFPs generally don't handle high current situations too well. 2. That is an appropriate solution to charge your bow thruster FLA.
A drop in battery like the Chins will not power the thruster, not enough starting or running current . Keep the 904D, charge via the ACR from the starter battery. The 80 Amp alternator should be OK with the typical 35 amp input of the Orion. Replace the solar controller with something better, Victron recommended.
The House, Bow Thruster and Start batteries are all within 5 feet or less of each other. The Bow Thruster is about 15 feet from it’s battery. Thank you all for validating my concern of the Bow Thruster’s heigh current draw on LFP’s. I will continue to keep the Bow Thruster on its’ own its’ dedicated 904D FLA battery.
The Bow Truster is a Lewmar 140TT 3hp 12V motor rated 280 Amps on the cable size diagram. 3. Yanmar Diesel Engine Start Battery is a lead acid Group 24 12V 780 CCA.