Verified Mathematical Model & Formulation
Usable Energy (Wh) = Battery Voltage (V) × Capacity (Ah) × Depth of Discharge (%) Runtime (Hours) = (Usable Wh × Inverter Efficiency) / Load (Watts)
Calculates total watt-hours of chemical storage, adjusts for safe depth-of-discharge (50% for Lead-Acid, 80-90% for Lithium LiFePO4), and factors in 85-90% DC-to-AC inverter conversion losses.
Configurable Parameters & Standard Units
- Battery System Voltage (V): (Default: 12 v)
- Battery Capacity (Ah): (Default: 100 ah)
- Continuous Load (Watts): (Default: 150 w)
- Depth of Discharge (50% Lead, 85% Lithium): (Default: 80 percent)
- Inverter Efficiency (%): (Default: 90 percent)
Standard Worked Example & Practical Verification
Scenario: Running a 120W mini fridge on a 12V 100Ah LiFePO4 battery (85% DoD) via a 90% efficient inverter.
Calculated Solution
7.65 Hours of Continuous Backup Runtime
Practical Takeaway: Cycling a refrigerator with 33% compressor duty cycle will extend actual operational survival time to ~23 hours.
Frequently Asked Questions
Why shouldn’t Lead-Acid batteries be drained below 50%?
Deeply discharging standard lead-acid batteries below 50% state of charge accelerates irreversible plate sulfation and permanently shortens battery lifespan.