Battery Calculations

Using the beta? This page changes in the next FireCAD release, planned for December 1. See Battery Calculations (Preview).

Command

Prerequisites

• A FireCAD project must be open

Overview

Exports battery calculation reports per NFPA 72 requirements, showing standby current, alarm current, required battery capacity, and derating calculations for each panel.

Steps

1. Type ATEXPORT_BATTERY_CALCULATIONS in the AutoCAD command line
2. Select the panels to include
3. The report is generated as an Excel file

Calculation Formula

Required Ah = (Standby Current x Standby Hours + Alarm Current x Alarm Minutes/60) x Derating Factor

Default values (configurable in Options):

• Standby: 24 hours
• Alarm: 5 minutes
• Derating Factor: 1.2

Battery Size Selection

FireCAD sizes the battery automatically. It picks the smallest battery in the panel's available size list that meets the calculated required Ah, so it will land on a smaller battery (for example 12V 8AH) whenever that size is enough to cover the load, and it will only step up to a larger battery when the requirement exceeds the smaller one.

To make the calculation reflect a larger battery than the one it auto-selects (for example 12V 18AH instead of 12V 8AH):

• Change the minimum battery size for that panel so the calculation starts at the larger battery, or
• Type the size you want directly into the battery-size field in the battery calculation table.

Either option makes the report reflect the larger battery. If the size you need is not offered at all for a panel, contact support to have it added to the panel's battery list.

Report Options

The Select Circuits dialog includes a Battery Calculation Settings tab with options specific to this report:

• Show Speaker Currents (W ÷ V = A) — Converts speaker wattage to alarm current using the circuit voltage, so speakers appear in battery calculations alongside current-based devices
• Show Only Circuit Current Totals (Hide Part Details) — Collapses individual devices to circuit-level totals
• Include Cell Formulas — Embeds Excel formulas for standby/alarm current totals
• Include Circuits Without Current — Shows circuits that have zero standby and alarm current
• Ignore Spare Circuits — Excludes spare/unused circuits from the report

Tips

• Battery calculation parameters are configured in Options & Configuration under the Reports tab
• NFPA 72 Section 10.6.7.2 defines the 24-hour standby + alarm time requirements

Related Commands

• Panel Summary Report
• Options & Configuration

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