Evaluating Battery Replacement Options on my Crusing Sailboat

DIY
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Hello, I’m new to this forum. The time has come for me to replace the batteries on my 36’ coastal cruising sailboat (Long Island, NY). The existing setup is shown below. I do not have a dedicated starting battery, but always start the motor on “both”. The main things i want to consider are: Fitting in existing space, weight, cost, complexity, capacity and robustness for occasional discharge >50%. I’m right on the edge of the 100ah overnight limit this setup gives me. I switch batteries each morning when at anchor and as long as we have moderately sunny days, the solar is all i need to recharge the battery from the night before and keep up with demand during the day so that the in use battery is still fully charged in late afternoon, ready for the overnight demand.

The diagrams do not show the smart shunts i have on each battery, but they are there and monitor my usage.

Option 1 is direct replacement with FLA

Option 2 is change to 2 AGMs: 2 x200ah Renogy, 2x220ah or 2x240 ah Victron Standard or 2x170 ah Victron Super Cycle

Option 3 is change to a single ~300ah LiFePo for the house and add a dedicated starting battery

Option 4 is a single ~300ah LiFePo House battery and a dedicated LiFePo starting battery

Comparison Spreadsheet below diagrams.

Questions:

  • Do the schematics look correct?
  • Did i miss anything on the schematics or spreadsheet?
  • In setups 3 & 4, will the “extra” solar wattage from the starter battery MPPT help charge the house battery thru the Orion?

Thanks! Paul, S/V BlueMoon

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2

This is the one I like:

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The house battery can be Lithium, provided that the max alternator voltage is less than the battery’s maximum voltage.
Solar can be added to either or both batteries, if the starter battery is charged from solar, and the voltage rises to 13.8 (approx) then the relay will close and the house battery will also be charged.
You can also add an AC charger, one or 2 output, and battery isolator switches to meet code. A dual battery switch is not needed, as the cyrix can bridge the batteries if needed.