PreBuild Engineering
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Free tool · PreBuild Engineering

Battery life calculator for low-power devices

Estimate how long an ESP32 or other battery-powered device will run on a given battery.

Inputs

mAh
%
Allow for cutoff voltage, temperature and aging
mA
s
µA
min

Result

—

Why it matters

Battery-powered products are judged on battery life, and the real number is often set by a regulator's quiescent current or a slow Wi-Fi connect rather than the MCU's sleep current.

Formula

I_avg = (I_active · t_active + I_sleep · (T − t_active)) / T Life (h) = Capacity · usable% / I_avg

Design tips

  • Measure real currents with a power profiler: datasheet sleep figures rarely include the whole board.
  • Self-discharge matters for multi-year designs, especially with Li-ion.

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Results are engineering estimates from standard formulas and published approximations. Always confirm against component datasheets, your fabricator's capabilities and, for critical designs, simulation or measurement.