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Marine Battery Bank Sizing Calculator

Amp-Hour Capacity, Battery Count, and Charging Requirements for House, Starting, and Bow Thruster Banks per ABYC E-10

Free marine battery bank planning calculator for early vessel electrical conversations. Enter daily DC load rows, select a local chemistry row, and compare a local house-bank amp-hour calculator, starting-bank CCA proxy, temperature factor, weight calculator, and battery example rows.

Outputs are source-gap planning aids only. Actual house-bank capacity, starting-battery rating, battery count, charge-source design, alternator protection, conductor and OCPD sizing, battery location, ventilation, lithium BMS behavior, ignition protection, mounting, survey acceptance, and safe installation require current ABYC standards, exact battery and engine manuals, charger/alternator product data, and qualified marine-electrician or ABYC-technician review.

Pro Tip: Use this calculator to build a complete battery and load checklist before buying hardware. Replace every preset amp-hour, DoD, temperature, weight, and group-size row with measured loads and exact manufacturer data, then verify charging sources, protection, ventilation, lithium BMS limits, and installation requirements separately.

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Marine Battery Bank Sizing Calculator
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How It Works

  1. Build Your Load Audit

    List each DC load, then replace presets with measured current, nameplate current, duty cycle, and realistic daily run time for your vessel.

  2. Select Local Chemistry Rows

    Choose a planning chemistry row while treating DoD, temperature, weight, and charge behavior as manufacturer-specific source gaps.

  3. Set Autonomy Assumptions

    Enter the local autonomy calculator, then verify the result against actual charging access, passage plan, weather, alternator limits, solar output, and shore-power behavior.

  4. Carry Source Gaps Forward

    Use the export as a checklist for battery datasheets, engine starting requirements, charger settings, BMS limits, ABYC review, fusing, disconnects, ventilation, mounting, and qualified installation review.

Built For

  • Cruising sailors building a preliminary load checklist before marine-electrician review
  • Marine electricians gathering source-gap assumptions before specifying battery and charger hardware
  • Boat builders documenting local house-load assumptions before standards and product review
  • Liveaboards comparing capacity and weight screens before verifying charging and installation details

Features & Capabilities

Daily Load Audit Worksheet

Local load-entry table with common marine loads. Enter amps and hours for each load, then replace presets with measured or manufacturer data.

Local Chemistry Rows

Flooded lead-acid, AGM, gel, and lithium LFP rows are planning placeholders for DoD, temperature, and weight until exact datasheets are reviewed.

Charging Source Review Prompts

Flags that alternator, shore charger, DC-DC, solar controller, regulator, and inverter/charger compatibility require separate product review.

Source-Boundary Export

Reports carry ABYC, battery datasheet, lithium BMS, protection, ventilation, and qualified-review warnings forward.

Frequently Asked Questions

Multiply each device current by realistic daily run time, then verify intermittent-duty loads with measurements or manufacturer data. A refrigerator, autopilot, bilge pump, inverter, or electronics package can vary widely by vessel and conditions.
Use the local DoD row only for early screening. The exact usable capacity, cycle-life tradeoff, low-temperature behavior, BMS limit, warranty condition, and charger profile come from the selected battery datasheet and manufacturer instructions.
Autonomy depends on route, weather, crew behavior, solar harvest, engine run time, shore power, generator use, and reserve requirements. Treat the app output as an estimate, not a passage-readiness decision.
Lithium can reduce weight and increase usable capacity, but the selected battery, BMS, enclosure, alternator protection, low-temperature charging, fire-risk controls, listing, ABYC E-13 review, and manufacturer support decide whether it fits the vessel.
Disclaimer: This tool provides preliminary source-gap planning screens only. It is not an ABYC compliance determination, marine survey, final starting-battery selection, lithium installation approval, charger or alternator design, conductor/OCPD selection, ventilation design, or safe-installation approval. Verify current standards, manufacturer data, vessel conditions, and qualified marine-electrician or ABYC-technician review before purchase or installation.

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