Marine Battery Calculators
Design reliable marine battery systems with engineering-grade calculators. Size house banks for cruising, estimate runtime for hotel loads, and plan charging systems.
Marine battery systems operate in one of the most demanding electrical environments: constant vibration, humidity, salt air exposure, and the critical requirement that the system must work reliably when you are miles from shore. Unlike automotive or residential applications, a marine battery failure can leave you without navigation, communication, or propulsion in dangerous conditions.
Marine electrical design starts with a thorough hotel load analysis. Hotel loads are all the electrical loads on your vessel that operate while at anchor or underway: navigation electronics (chartplotter, radar, AIS, VHF radio), cabin lighting, refrigeration, water pumps, bilge pumps, windlass, and entertainment systems. A typical cruising sailboat draws 50–100Ah per day at anchor. A motor yacht with air conditioning and galley appliances can draw 200–500Ah per day.
Battery bank sizing for marine applications must account for the marine environment's unique challenges. Vibration from engine operation and wave action can damage batteries not designed for marine use. Temperature extremes in engine compartments can accelerate degradation. Salt air corrosion affects terminals and connections. Marine-grade batteries address these concerns with reinforced construction, sealed cases, and corrosion-resistant terminals.
ABYC (American Boat and Yacht Council) standards specify requirements for marine electrical systems, including battery installation, wiring, and overcurrent protection. Any marine battery installation should comply with ABYC E-11 (AC and DC Electrical Systems on Boats) and ISO 13297 (Electrical installations in boats). Our calculators provide the sizing foundation, but installation must meet these standards.
Available Calculators
Marine Battery Sizing Calculator
Size your boat house bank based on hotel loads, usage hours, battery voltage, and depth of discharge.
Yacht Battery Runtime Calculator
Estimate how long your marine battery will power navigation, lighting, refrigeration, and entertainment systems.
Hotel Load Calculator
Convert between Ah and Wh to match your boat's hotel load requirements with battery bank capacity.
Marine Battery Guides
Marine Battery Sizing Guide
LEARNING CENTERBoat Battery Runtime Guide
LEARNING CENTERYacht Battery Planning
LEARNING CENTERMarine Hotel Load Guide
LEARNING CENTERLithium Marine Batteries
LEARNING CENTERHow to Size a Battery Bank
LEARNING CENTERBattery Sizing Reference
LEARNING CENTERBattery Depth of Discharge Chart
LEARNING CENTERBest Battery Chemistry for Marine
LEARNING CENTERMarine Battery Voltage Selection
Frequently Asked Questions
How do I size a marine battery bank?
Inventory all hotel loads on your vessel (navigation, lighting, refrigeration, pumps, electronics), estimate daily usage hours for each, calculate total daily energy consumption in Wh, and divide by your system voltage and depth of discharge to get the required bank capacity in Ah. Our Marine Battery Sizing Calculator automates this process.
What battery chemistry is best for marine use?
LiFePO4 is increasingly preferred for marine house banks due to its deep discharge capability, vibration resistance, and maintenance-free operation. AGM lead-acid remains common for engine starting due to its high burst current. Many marine electricians recommend a dual-bank setup: lithium for house loads and AGM or lithium for engine starting.
How long will my marine battery last while anchored?
A typical cruising yacht with a 400Ah 12V LiFePO4 house bank can run navigation electronics, cabin lighting, refrigeration, and water pumps for 2–3 days at anchor without charging. Adding solar panels or running the engine alternator extends this significantly. Runtime depends heavily on your specific load profile and whether you are running energy-intensive appliances.
Do I need a battery monitor for my boat?
Yes. A battery monitor (shunt-based coulomb counter) is essential for marine battery systems. It tracks state of charge, current draw, time remaining, and historical usage patterns. Unlike voltage-based SOC estimation, a coulomb-counting monitor provides accurate readings regardless of load-induced voltage sag, which is critical for preventing deep discharge events.
What is the difference between marine house and starting batteries?
House batteries are designed for deep, sustained discharge cycles to power hotel loads. Starting batteries deliver high burst currents (hundreds of amps) for short durations to crank the engine. Using a starting battery for house loads will damage it quickly. Using a house battery for starting works but may not deliver sufficient cranking amps for large engines.