ProcirelEstimate how long a battery will last based on its capacity (mAh) and the circuit’s average current draw (mA). An optional efficiency factor accounts for real-world losses due to voltage regulation, battery chemistry, temperature, and discharge rate characteristics.
How to use this calculator
Step-by-Step Instructions
1. **Enter battery capacity** Find this on the battery label (e.g., 18650 cells are typically 2000-3500mAh, 9V battery ~500mAh, AA ~2500mAh).
2. **Enter average load current** Measure or calculate the average current draw of your entire circuit in milliamps (mA).
3. **Adjust efficiency** Use 85-90% for Li-ion batteries with efficient regulators, 70-80% for alkaline batteries or inefficient circuits.
4. **Click Calculate** Result shows estimated runtime in hours and days.
Worked Example
A 2000mAh Li-ion battery powering an ESP32 WiFi module drawing 150mA average:
(2000 × 0.85) ÷ 150 = **11.3 hours**