Starter Battery vs Lithium House Bank
Learn why many yachts keep a dedicated engine-start battery while using LiFePO4 for the house bank.
A starter battery and a house bank do different jobs.
A starter battery is designed for very high current for a short duration. A house bank is designed for repeated cycling to run refrigeration, electronics, lighting, pumps, communications and inverter loads.
Why many lithium conversions keep a lead-acid starter
Keeping the existing AGM or flooded starting battery can preserve a proven engine-start architecture, isolate house BMS shutdown from starting, simplify alternator integration and provide functional separation between starting and house energy.
A DC-DC charger can transfer controlled energy from the alternator/start side to the lithium house bank.
Some lithium products are specifically designed for engine starting, but ordinary deep-cycle LiFePO4 batteries should not be assumed suitable for cranking.
Make the installation verifiable
A credible marine installation should be inspectable, documented and recoverable after a protection event. The battery label alone cannot show whether fault current, isolation, charging control, mounting and essential services have been addressed.
- Document cable sizes, protection ratings, isolation points, charging settings and BMS warning or shutdown logic.
- Confirm that terminals are protected, equipment is restrained and the location is suitable for heat, water and service access.
- Have the completed system commissioned and retain the drawings, settings, test results and equipment manuals aboard.