Example Data Table
| Item | Qty | Standby A | Alarm A | Use |
|---|---|---|---|---|
| Main Circuit Board | 1 | 0.110 | 0.214 | Base panel load |
| ANN-80 | 1 | 0.015 | 0.040 | Remote annunciator |
| NAC 1 | 1 | 0.000 | 0.600 | Horn strobe circuit |
| TB9 Load | 1 | 0.080 | 0.080 | Auxiliary device power |
Formula Used
Standby load: Sum of quantity multiplied by standby current.
Alarm load: Sum of quantity multiplied by alarm current.
Standby AH: Standby load × standby hours.
Alarm AH: Alarm load × alarm minutes ÷ 60.
Required AH: (Standby AH + Alarm AH) × derating factor.
Battery pass check: Installed battery AH must be equal to or greater than required AH.
How to Use This Calculator
- Enter the project name, job number, and preparer name.
- Keep 24 standby hours and 5 alarm minutes unless your project requires another value.
- Enter each module, detector, NAC, and auxiliary load.
- Use amps, not milliamps. Divide milliamps by 1000 first.
- Press the calculate button.
- Review AH results, charger warnings, cabinet warnings, and NAC warnings.
- Download the CSV or PDF for records.
Battery Calculation Sheet Guide
Battery Sheet Purpose
A fire alarm panel must run during power failure. The Fire-Lite MS-5UD-3 uses standby batteries for that duty. This sheet turns many small current values into one battery size. It separates quiet operation from alarm operation. That split matters because horns, strobes, relays, and modules do not always draw the same current.
Why Accurate Loads Matter
Battery sizing is not a guess. A low value can leave the system short during an outage. A high value may force larger cabinets, added chargers, and extra cost. The goal is a practical value that fits the listed equipment and the authority review. Each row lets you add quantity, standby current, and alarm current. The calculator then multiplies quantity by current.
Standby and Alarm Time
Most local fire alarm designs use twenty four hours of standby. They then add five minutes of alarm. Some projects need longer alarm time. Some jurisdictions ask for special survivability rules. This sheet lets you change both times. It also keeps the common derating factor visible.
Device Rows
The sheet includes rows for the main board, optional transmitters, converters, annunciators, detectors, NAC circuits, TB9 power, and spare items. Built in defaults help start the review. User entered currents should still come from approved device data. Always use the exact model, candela, sync setting, relay state, and detector count.
Review Notes
After calculation, check the required amp hours against the selected battery. Also check charger and cabinet limits. The MS-5UD-3 has limits that must not be ignored. If the result is above the allowed range, use an approved external charger and listed battery cabinet. Keep a copy with the riser, submittal, and as built records.
Practical Workflow
Start with the panel current. Add modules one by one. Enter every NAC load in alarm. Add standby detector loads and auxiliary device loads. Press calculate. Review warnings before printing. Export the CSV for spreadsheets. Export the PDF for clean job records. Then confirm the result with the project engineer and local authority.
Use measured values when available. Label unknown loads clearly. Do not hide assumptions. A reviewer should see how every amp was found. This improves service notes, future battery changes, and final acceptance during every annual inspection.
FAQs
What does this sheet calculate?
It calculates standby load, alarm load, required amp hours, derated amp hours, and a recommended battery size for an MS-5UD-3 style fire alarm panel battery review.
Should I use milliamps or amps?
Use amps in every current field. Convert milliamps by dividing by 1000. For example, 80 mA becomes 0.080 A.
Why is a derating factor used?
The derating factor adds reserve capacity. It helps account for aging, tolerance, and practical field conditions. The common value shown is 1.2.
Can I change standby time?
Yes. Enter the required standby hours for your project. Many fire alarm designs use 24 hours, but local rules may require another value.
Can I change alarm time?
Yes. Enter alarm time in minutes. The form converts minutes into hours before calculating alarm amp hours.
Why are NAC loads alarm only?
Most notification appliances draw their significant current during alarm. Enter each NAC alarm load from the approved appliance current table.
What if required AH is above the charger limit?
The warning means the panel charger setting may not support that capacity. Review the manual, charger listing, battery cabinet, and authority requirements.
Is this a final engineering approval?
No. It is a calculation aid. Always verify device data, wiring limits, local code, engineer requirements, and authority comments before installation.