Battery Backup Calculator

Calculate backup time and power requirements for battery systems

Battery Backup Calculator

Professional Battery Backup Time Estimation

Results:

Backup Time: 0.00 hours

Backup Time: 0 minutes

Usable Capacity: 0.00 Wh

Battery Energy: 0.00 Wh

Lithium Battery Backup Calculator
Battery Life Calculator

How to Use the Calculator

Battery Specifications

  1. Select battery voltage (12V, 24V, 48V or custom)
  2. Enter battery capacity in Amp-hours (Ah)
  3. Input the total load power in watts
  4. Set system efficiency percentage
  5. Configure depth of discharge limit

System Efficiency

  1. Typical inverter efficiency: 85-95%
  2. DC systems: 90-98%
  3. Include all conversion losses
  4. Consider cable and connection losses
  5. Account for temperature effects

Depth of Discharge

  1. Lead-acid: 50-80% recommended
  2. Lithium: 80-95% safe range
  3. AGM batteries: 50-80%
  4. Gel batteries: 50-70%
  5. Higher DoD reduces battery life

Battery Backup Fundamentals

Battery Capacity

Battery capacity determines backup duration:

  • Measured in Amp-hours (Ah)
  • Energy = Voltage × Capacity
  • Temperature affects capacity

Load Calculation

  • Sum all connected device power
  • Consider startup surge currents
  • Account for continuous vs peak loads

Key Formulas:

Backup Time = (Battery Voltage × Capacity × DoD × Efficiency) / Load Power

Usable Energy = Battery Voltage × Capacity × DoD

Runtime (hours) = Usable Energy / Load Power

Calculation Formulas

Battery Energy:
Energy (Wh) = Voltage × Capacity (Ah)

Usable Capacity:
Usable = Energy × DoD × Efficiency

Backup Time:
Time (h) = Usable Capacity / Load Power

Example Calculation

12V Battery System:

Battery: 12V, 100Ah

Load: 200W

Efficiency: 85%

DoD: 80%

Battery Energy = 12V × 100Ah = 1200Wh

Usable = 1200 × 0.8 × 0.85 = 816Wh

Backup Time = 816Wh / 200W = 4.08 hours

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