What is House and Start Batteries?
Lead-acid batteries are the most common and include flooded, AGM and gel types. Lithium batteries, typically LiFePO₄, are increasingly popular due to lighter weight, longer cycle life, higher usable capacity and faster charging.
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What it is
Lead-acid batteries are the most common and include flooded, AGM and gel types. Lithium batteries, typically LiFePO₄, are increasingly popular due to lighter weight, longer cycle life, higher usable capacity and faster charging. Start batteries are designed to deliver short, high-current bursts to crank the engine, while house batteries supply steady power over longer periods to run equipment and systems.
What it does
Marine batteries provide electrical energy for starting the engine (start battery) and powering onboard systems such as lights, electronics, refrigeration, and pumps (house battery bank).
Why it matters
Battery failure can leave you stranded without engine power, which is particularly dangerous in storms or tight harbors. Dead house batteries disable essential systems such as navigation lights, VHF radios, bilge pumps, and GPS, compromising safety. Lead-acid batteries that are repeatedly discharged below 50% capacity can suffer permanent damage, reducing lifespan. Damaged or swollen batteries may leak acid, emit explosive hydrogen gas, or, in extreme cases, catch fire. Lithium batteries are more tolerant of deep discharges but still pose risks if overcharged, short-circuited or physically damaged. Most marine grade Lithium batteries have a built in BMS (battery management system) which protects the cells in case of overheating, overcurrent, cell imbalance or physical damage. Installing a 24V system can reduce amperage and allows for smaller cable sizing.
General Maintenance
Check battery terminals monthly for corrosion and loosening. For flooded lead-acid batteries, inspect electrolyte levels monthly and top up with distilled water as required. Perform a full load test on all batteries annually to verify capacity. Monitor resting voltage regularly. Replace batteries every 10 years or per manufacturer recommendations.
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