1. What is Backup Battery Runtime?

Backup battery runtime is the estimated duration a battery system can power electrical loads during an outage. It depends on battery capacity, voltage, discharge limits, system efficiency, and load power requirements.

2. How Does the Calculator Work?

The calculator uses the backup time formula:

Where:

• Battery Capacity — Total amp-hour rating of the battery
• Battery Voltage — System voltage (typically 12V, 24V, or 48V)
• Depth of Discharge — Fraction of battery capacity that can be safely used (typically 0.5-0.8)
• Efficiency — System efficiency accounting for inverter and other losses (typically 0.85-0.95)
• Load Power — Total wattage of connected devices

3. Importance of Backup Time Calculation

Details: Accurate backup time estimation helps design reliable power backup systems, select appropriate battery sizes, and manage power usage during outages.

4. Using the Calculator

Tips: Enter all values in the specified units. Typical values are 0.8 for Depth of Discharge and 0.9 for Efficiency if unsure. Load Power should be your total connected load in watts.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical depth of discharge for lead-acid batteries?
A: About 50% for flooded lead-acid, 80% for AGM/gel batteries to maximize battery life.

Q2: How does temperature affect runtime?
A: Cold temperatures reduce battery capacity - derate by 20-50% for temperatures below freezing.

Q3: Should I size my battery for peak or continuous load?
A: Size for continuous load, but ensure your inverter can handle startup surges for motors.

Q4: How often should I test my backup system?
A: Test monthly and perform full discharge tests annually to verify capacity.

Q5: Can I connect batteries with different capacities?
A: Not recommended as it leads to uneven charging/discharging and reduced performance.