Battery Life Calculator – Runtime with Sleep Current & Duty Cycle
Most battery-powered devices sleep most of the time. Runtime depends on the average current, which is dominated by sleep current more often than people expect.
mAh
= 2000 mAh (2 Ah)mA
= 80 mAmA
= 0.05 mA (50 µA)Type 50uA or 0.05 — both mean 50 µA%
0–100 %A factor between 0 and 1. 0.7–0.85 is realistic (0.8 = 80 %)
%/month
Li-ion ≈ 2–3, alkaline ≈ 0.2, NiMH ≈ 15–30Results
- Average current
- 1.705 mA
- Usable capacity
- 1600 mAh
- Runtime
- 938.7 h
- ≈ Days
- 39.11
- ≈ Months
- 1.28
Pro
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Runtime ≈ 39.1 days · avg 1.705 mA
Formula
- I_avg = I_active·d + I_sleep·(1−d)
- t = (C · derating) / I_avg
FAQ
- What derating should I use?
- 0.7–0.85 is a sensible start. Cold, high pulse currents and cut-off voltage all reduce usable capacity.
- Why is my real runtime shorter?
- Regulator quiescent current, LEDs, pull-up resistors and leakage add up. Measure sleep current with a proper µA meter.