Battery Life Calculator
Model a real recurring mission profile instead of dividing mAh by one average current. Tune four consumption modes, inspect the SVG timing diagram, and catch peak-current brownout risks before release.
Cycle current and mode timeline
The stepped trace is the regulated-rail current. Drag the probe to inspect the active mode and its input power at any instant in the mission cycle.
Click or drag either graph to move the probe. The lower view magnifies the real active-time window while preserving the exact macro-cycle above.
Sleep automatically fills unused time
Battery budget for this mission
Which mode spends the battery?
Each bar uses the actual energy of a mode within one cycle, not only its current. A short radio burst can therefore dominate a long sleep interval.
Hit an autonomy target
Set an autonomy goal and the costly mode to constrain. The assistant calculates a practical duration budget and the minimum interval between full mission cycles.
Battery-life guide
Turn a usage profile into credible battery life
A product’s runtime is not simply battery mAh divided by one current. It depends on time spent in each state—sleep, sensing, processing, radio, or peak load—plus the capacity actually usable and the system’s minimum acceptable voltage.
Method and assumptions
The calculator breaks a cycle into adjustable consumption modes. For each mode it multiplies current by duration, sums charge per cycle, and converts that into average current. Nominal capacity is then adjusted by the selected losses and compared with that budget. The timeline exposes peaks that barely affect the average but can still cause a brownout.
Inputs to verify
Mission profile
Set at least the four states that represent the product, for example sleep, sensing, processing, and transmission. A short cellular or radio transmission can consume as much energy as several minutes of sleep.
Actually available capacity
Enter capacity at the intended temperature, discharge rate, and age, then reserve margin for cutoff voltage, self-discharge, and regulator losses. A cell’s printed rating is rarely fully usable.
Peaks and operating threshold
Check peak current against cell internal resistance, reservoir capacitors, and the converter or microcontroller’s minimum voltage. A reassuring average does not protect against a transient voltage dip.
Recommended workflow
- 1Describe one real cycle, from wake-up through return to sleep, then adjust every mode’s duration and current on the timeline.
- 2Compare each mode’s charge with the total budget: optimise the state that dominates energy first, not merely the one with the highest instantaneous current.
- 3Apply capacity margins, check the critical peak, then compare the projection with measurements on a representative prototype.
Decision example
A sensor that sleeps at 10 µA, measures for 200 ms at 4 mA, processes for 50 ms at 8 mA, then transmits for 2 s at 80 mA every 15 minutes is dominated by transmission. Halving sleep current helps little; shortening or spacing transmissions can improve runtime substantially.
Limits to keep in mind
This estimate does not replace a manufacturer discharge curve or climatic test. Capacity varies with chemistry, temperature, ageing, current pulses, and cutoff voltage; rechargeable packs also require validation of charging safety and protection circuitry.
Frequently asked questions
Why does a 2,400 mAh cell not always run for 2,400 hours at 1 mA?
Capacity is measured under specific conditions. Cold, age, conversion losses, self-discharge, quiescent current, and an early cutoff all reduce recoverable energy. Peaks can also reach the cutoff voltage long before all nominal charge is extracted.
Which mode should I optimise first?
Look at charge per cycle—current × duration—rather than current alone. A very short state can have the highest current without dominating runtime; conversely, a small continuous sleep current can become dominant.
References to consult
- Method references: cell discharge and impedance curves at the target temperature, regulator efficiency and quiescent current, and product current measurements over its real cycle.
Original educational content, reviewed for technical clarity on 20 August 2026. Always verify datasheets, applicable standards, and your design before power-up or manufacture.