Battery Life Calculator

Estimate runtime from capacity and current draw.

Values

Battery capacity (mAh) Average current draw (mA) Converter efficiency (%)

85% ≈ DC-DC converter · 100% ≈ direct connection

Result

≈ 17.0 h (1699 mAh usable)

Estimating battery runtime

Runtime is capacity divided by current: t = Q / I. Real circuits lose energy in voltage regulators and DC-DC converters, so multiply by efficiency: t = Q·η / I. A 2000 mAh cell driving 100 mA at 85% efficiency gives about 17 hours.

For a rough "usable capacity" rule, subtract 10–20% because batteries don't deliver their full rated capacity at high discharge rates.