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TOOL-Battery Backup Time Calculator
Battery Backup Time Calculator
Deep-green · White fonts · Result-oriented
Inputs
Tip: Ideal = (V × Ah) ÷ Load. Real-world also applies efficiency & DoD.
Results
Enter values and hit Calculate.
–.– h
Ideal estimate
–.– h
Real-world estimate (efficiency + DoD)
Usable Energy
– Wh
Current Draw
– A
Result Link
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Quick FAQ
How do I match the example 12V, 225Ah, 300W?
Use V=12, Ah=225, Load=300, Efficiency=100%, DoD=100% to get ≈ 9 hours (ideal). With 85% efficiency & 80% DoD, the realistic estimate is ≈ 6.12 hours.
What is DoD?
Depth of Discharge is the portion of capacity you plan to use. Many lead-acid batteries are kept to 50–80% DoD to extend life; lithium often allows more.
What affects runtime?
Load wattage, inverter efficiency, temperature, battery age, discharge rate (Peukert effect for lead-acid), and actual DoD.
