UPS battery sizing calculator

Use this calculator when the work question starts with a target UPS runtime. Instead of asking how long an existing UPS battery energy value may last, the page estimates the Wh and Ah capacity implied by an entered load, runtime target, DC bus voltage, efficiency and reserve allowance.

The result is a sizing worksheet, not a product selector. UPS battery capacity depends on product curves, battery configuration, age, temperature, discharge rate, end voltage and manufacturer data. The calculator keeps the arithmetic visible so the record can be checked against those sources later.

UPS Battery Sizing Use Cases

A strong record names the UPS load group and runtime target. A required Ah value without load, voltage and reserve basis is weak evidence and can be misleading when copied into product discussions.

Battery Sizing Boundary

This boundary keeps the worksheet focused on transparent energy arithmetic. A capacity estimate can help discussion, but product selection should use manufacturer data and the actual supported load profile.

Input Checklist

If the load is not steady, create separate records for the scenarios that matter. A single average can hide the supported load that controls battery size.

Review Workflow

1. Name the UPS, load group or backup capacity record.
2. Enter the load in watts.
3. Enter the runtime target in minutes.
4. Enter the nominal UPS DC bus voltage.
5. Enter efficiency from product data or a documented planning basis.
6. Enter reserve allowance as a visible percentage.
7. Read load energy before using the Ah result.
8. If reserve is high, confirm the basis.
9. If required capacity is large, check UPS product range and battery data.
10. Keep manufacturer curves, battery condition, installation requirements and project decisions outside this worksheet.

The workflow separates output energy, DC energy and stored energy. That separation helps a reviewer see whether load, efficiency, reserve or voltage is driving the capacity estimate.

Worked Records

Australian Context

UPS battery sizing records in Australia may feed backup power, power-quality, communications and critical-load discussions for 230/400 V, 50 Hz installations. This page stays on energy arithmetic. Installation requirements, product instructions, battery replacement policy, bypass arrangements, ventilation, local authority expectations and project requirements remain outside the calculator.

When the result feeds a project decision, check UPS manufacturer data, battery manufacturer data, site conditions and project requirements. Treat the calculator output as an entered-data worksheet rather than an equipment selection.

Stop Points

• Load basis is unknown or averaged across unlike backup scenarios.
• Runtime target is not supported by project or operating requirements.
• DC bus voltage does not match the intended UPS battery arrangement.
• Reserve is copied without product or project basis.
• Ah result is being treated as product selection or site approval.