TheCircuitDogPower Design
Battery Runtime Calculator
Estimate how long a battery can power a roughly constant load after usable capacity and conversion losses.
Enter the values above and select Calculate result.
Formula
Runtime (h) ≈ V × Ah × usable fraction × efficiency / load watts
Worked example
12 V × 10 Ah = 120 Wh nominal. At 80% usable and 90% efficiency, about 86.4 Wh remains; a 20 W load runs about 4.32 hours.
Engineering notes
Real runtime depends on temperature, C-rate, aging, battery chemistry and cutoff thresholds. Do not use this as a safety-critical endurance certification.
Always compare calculated values with the actual component datasheet, tolerance stack-up, operating temperature and circuit conditions before applying them to hardware.