Fire Lite Battery Planning Guide
Battery sizing protects a fire alarm control panel during utility loss. A good estimate separates standby load from alarm load. Standby load runs for many hours. Alarm load runs for a short emergency period. This calculator joins both demands in amp hours. It also adds reserve values for aging, temperature, and design safety.
Why Accurate Sizing Matters
Undersized batteries can drop panel voltage too early. That can cause trouble signals. It can also weaken notification appliance output. Oversized batteries may exceed charger limits. That can create inspection issues and slow recovery after discharge. A balanced result helps designers, installers, and maintenance teams choose a safer capacity.
Inputs You Should Review
Start with the standby current for the panel and connected devices. Use documented current values where available. Add detector, module, communicator, relay, and auxiliary loads. Then enter alarm currents for NAC circuits, horns, strobes, relays, and accessories. Keep all current values in milliamps. The form converts them into amps during calculation.
Derating And Reserve
Real batteries age. Capacity also changes with temperature and discharge depth. The margin field gives extra room for small design changes. The aging field helps model capacity loss over service life. The temperature derating field reduces usable capacity in poor environments. Depth of discharge limits how much stored energy should be used. These values make the result more conservative.
Interpreting Results
The required capacity is the final battery amp hour need. The selected battery capacity shows what one battery string can provide. The tool also checks the proposed number of parallel strings. It compares the installed capacity with the calculated demand. It also warns when the charger rating is below the installed capacity.
Best Practice
Use this estimate as a design aid. Verify final values with the control panel manual. Confirm local code, authority requirements, and manufacturer limits. Recheck loads after field changes. Save the CSV or PDF report for project records. A clear report supports review and future maintenance.
Retest assumptions yearly. Batteries do not stay equal forever. Labels can fade. Loads can change after renovations. A saved worksheet makes updates faster. It also helps technicians understand earlier choices during service calls and inspections. Keep a signed copy on site.