Battery life calculator
A sleep/wake product barely lives on its active current — it lives on the sleep current nobody measured. Enter the duty cycle and get an estimated run time, with the share of energy spent asleep versus awake.
An estimate from the numbers you give — not a guarantee. Measure the real board for anything that matters.
The formula
Iavg = Isleep · (1 − duty) + Iactive · duty + Ileak Life = Capacity · (1 − derate) / Iavg
When to use it
Sizing a coin cell or a small LiPo for anything that mostly sleeps: sensors, beacons, remotes, anything on a wake timer. It is an estimate, not a spec — real sleep current depends on the exact firmware, the regulator and every peripheral left half-awake, and it drifts with temperature and age, which is what the derating margin is for.
Pitfalls
- Sleep current is almost always higher than the datasheet’s “typical” figure once a regulator, a pull-up or an unconfigured peripheral is drawn into the measurement. Measure the real board before trusting a number.
- Capacity falls at low temperature and with age; the derating margin (default 20 %) is a starting guess, not a guarantee — cold environments or a long product life deserve more.
- Self-discharge is a steady leak even while nothing runs. Lithium chemistries are usually under 2–3 %/month; alkaline and some lithium primaries can be lower, but a stored product still loses capacity waiting on a shelf.
- A wake interval shorter than the active burst itself is not sleep at all — if the two are close, the “sleep” current barely matters and the active number dominates.
Related note
Why sleep current is higher than the datasheet saysNeed a real power budget? We measure your board’s actual sleep current and tune the firmware to reach it.