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Battery Bank Size Calculator

Estimate the nominal battery energy and capacity required to support a load for a chosen backup period, accounting for usable depth of discharge and system efficiency.

Backup requirement
Battery unit comparison
Depth of discharge is an input, not a battery-type rule. Enter a usable DoD and efficiency appropriate to the actual battery chemistry, BMS/manufacturer limits, inverter and operating conditions. Nameplate energy is not the same as usable delivered AC energy.
Waiting for calculation
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Your battery-bank planning result will appear here after you click the button.

—AC energy required
—nominal battery energy required
—bank capacity at selected DC voltage
—battery units / modules
Battery-bank voltage—
Usable DoD / efficiency—
Capacity margin—
Selected battery unit—
Proposed nominal bank from whole units—
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Battery design boundary: This is an energy-capacity planning calculator. It does not verify battery discharge-current capability, C-rate, BMS limits, inverter compatibility, series/parallel rules, cable/protection sizing, charging current, solar recharge time, generator/grid charging, temperature derating, battery balancing or manufacturer-approved configurations. For lead-acid batteries, high discharge rates and ageing can reduce practical capacity; for lithium systems, BMS and manufacturer limits govern. Use matched batteries and professional system design.

How the calculation works

Required AC energy = average load × backup hours. Nominal battery energy = AC energy ÷ (system efficiency × usable depth of discharge), then the selected capacity margin is added. Equivalent Ah = nominal watt-hours ÷ battery-bank voltage. For V/Ah batteries, the calculator determines the series count needed to reach the selected bank voltage and the parallel strings required to meet capacity, then shows the resulting whole-battery configuration. For kWh modules, it rounds required nominal energy up to whole modules.

How to Use and Check Your Result

Enter the measurements, quantities, costs and assumptions requested in the calculator above. Use its calculation control and review the displayed result. All figures should be checked against your actual project or operating conditions.

Planning and safety: Electrical or power-system sizing requires qualified design review and applicable safety standards. Finelib does not certify engineering designs or supplier quotations.

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Frequently Asked Questions

What does the Battery Bank Size Calculator estimate?

It estimates planning quantities or costs from the figures you enter. Review the calculator assumptions before using the result.

Can I use this calculator for a project in Nigeria?

Yes. Enter measurements and quotations relevant to your Nigerian location and project.

Does Finelib supply current market prices automatically?

No. Prices and rates should be checked with relevant suppliers; do not assume any illustrative values are live quotations.

Are the results guaranteed to be accurate?

No. The output depends on entered assumptions and is intended for preliminary planning, not professional certification.

How should I handle wastage or losses?

Where the calculator provides a wastage or contingency field, enter an allowance appropriate to the project. Otherwise account for it separately.

Can I use the result to request supplier quotes?

Yes. Use Finelib Match to find suitable businesses and request Quotes or Offers, then verify specifications and providers.

Should a professional review the result?

Yes, when the decision involves structural safety, electrical safety, major equipment, significant expenditure or regulatory requirements.