Fire Alarm Battery Planning
A fire alarm battery sheet proves that a system can run during power loss. It combines standby load, alarm load, required time, and practical reserve. The sheet also helps designers compare selected batteries with cabinet limits and charger ratings. Good records reduce review comments and speed field service.
What The Sheet Checks
The main check is amp hour demand. Standby current runs for many hours. Alarm current runs for fewer minutes but can be much higher. Notification appliances, relays, modules, communicators, and auxiliary loads must be included. This calculator separates those values, so the final number is easy to audit. It also adds expansion, safety, and derating allowances.
Useful Design Approach
Start with approved device current data. Use standby current for normal operation. Use alarm current for full system activation. Enter the required standby duration and alarm duration from the project basis. Many projects use twenty four hours of standby and five minutes of alarm. Some facilities need longer alarm time. Always follow the adopted code, authority requirements, and equipment listings.
Why Margins Matter
Batteries lose capacity with age, heat, cold, and repeated discharge. A calculated load that barely fits the battery may fail later. Expansion margin supports small future device additions. Safety margin covers measurement differences and schedule changes. Derating accounts for less than ideal battery performance. These inputs turn a basic calculation into a more realistic sheet.
Review And Documentation
The result table shows standby amp hours, alarm amp hours, raw demand, adjusted demand, and a recommended standard battery size. It also checks the selected battery, charger rating, and cabinet limit. Export the CSV file for spreadsheets. Export the PDF file for compact submittals. Keep the sheet with shop drawings, record drawings, and inspection notes.
Final Checks
A calculator cannot replace listed equipment instructions. Battery charging limits, enclosure space, conductor voltage drop, and supervision rules still matter. Recheck every device after equipment changes. Confirm that two series batteries are matched when a panel uses a twenty four volt supply. Replace batteries according to maintenance findings, manufacturer instructions, and local requirements.
Compare calculations against sheets and field measurements. Review commissioning records before submitting the battery schedule for approval. It also supports later maintenance and troubleshooting.