Battery Life Calculator

Estimate IoT device lifetime from duty cycle, current draw, usable capacity, reserve margin, and self-discharge.

A beginner-first battery life workbench with scenario presets, duty-cycle timeline, average-current calculation, battery derating, peak-current warning, and target-life feedback.

Animation Beginner first Battery life Duty-cycle math

Battery Life Calculator

Build an IoT power profile and watch each sleep, active, and radio phase turn into average current, usable battery capacity, and deployment lifetime.

4.8 years estimated deployment life

51.2 uA total average current

2160 mAh usable battery capacity

Meets target target-life status

Goal

Estimate lifetime from the current used in each mode, not from battery capacity alone.

Try First

Increase the wake interval and watch average current fall faster than you may expect.

Watch

The biggest energy consumer may be sleep current, radio bursts, or self-discharge.

Why It Matters

A device that works on the bench can fail deployment targets if the power budget is wrong.

Controls

Choose a battery and scenario, then tune the duty cycle and environment.

Scenario room sensing

Battery disposable AA pair

Playback manual

Wake interval 5 min Longer intervals usually reduce radio and active energy per hour.

Sleep current 15 uA Sleep current runs almost all the time in many IoT devices.

Active current 8 mA Sensor reading and CPU work before the radio burst.

Active time 0.6 s Shorter firmware paths reduce energy per wake event.

Radio current 45 mA Peak radio current must be supported by the battery and regulator.

Radio time 80 ms Payload size, retries, and protocol choice change this value.

Temperature 22 C Cold operation reduces usable capacity and increases voltage sag.

Target life 18 months Use this as a design target, not as a guaranteed field result.

Reserve margin 10% Reserve leaves capacity for aging, variation, and shutdown margin.

1. Profile Choose the battery and device behavior you want to estimate.

2. Duty Cycle Each wake interval contains sleep, active work, and radio time.

3. Average Convert bursty current into one average-current number.

4. Capacity Derate the rated battery capacity for reserve and temperature.

5. Lifetime Divide usable capacity by total average current.

0.23% awake duty cycle

1.14 uAh energy per wake event

8.2 uA self-discharge equivalent

11.1x radio peak margin

Duty-Cycle Timeline

The cycle shows how a short wake event is averaged across a much longer sleep interval.

Near target

Reading: The average current is dominated by the sleep baseline and radio burst energy spread across the wake interval.

Live Calculation

A room sensor wakes every few minutes, samples quickly, and sends a short packet.

Average current

Sleep contribution0.015 mA

Active contribution0.016 mA

Radio contribution0.012 mA

Self-discharge8.2 uA

Capacity and life

Rated capacity2400 mAh

Usable capacity2160 mAh

Estimated life4.8 years

Design flags

This estimate meets the target as an early design check. Measure real current before committing a battery size.

Formula Check

Lifetime comes from usable capacity divided by total average current.

2160 mAh / 51.2 uA

Dominant Cost

The largest average-current contributor is the main optimization target.

sleep baseline

Battery Fit

The selected battery can supply the configured radio burst with margin.

Peak OK

Beginner Ramp

Battery life is mainly a capacity and average-current problem.

• mAh: milliamp-hours, a battery capacity unit.
• mA: current draw, or how quickly charge is used.
• Average current: the bursty device current smoothed over time.

Duty Cycle

Most IoT nodes should sleep almost all the time and wake briefly to sense or transmit.

• Longer wake intervals reduce active and radio energy per hour.
• Sleep current still matters because it runs continuously.
• Radio retries can quietly multiply energy per message.

Formula Reference

phase mAh = current mA x seconds / 3600

average current = cycle mAh / cycle hours

life hours = usable mAh / total average mA

Usable Capacity

Rated capacity is measured under specific test conditions. Real deployments need margin.

• Cold temperatures can reduce usable capacity.
• Reserve margin helps cover aging and cell variation.
• Small cells may not support high peak current even if mAh looks sufficient.

Self-Discharge

Batteries lose charge even when the device draws almost no current.

• Self-discharge is small for short deployments.
• It becomes important for multi-year sensors.
• Rechargeable cells often have higher self-discharge than primary cells.

Measurement Note

This calculator is a design estimate. Final battery choice should be checked with measured current traces.

• Measure sleep current after all peripherals are configured.
• Capture radio bursts with enough bandwidth.
• Test at the coldest expected deployment temperature.

Practice 1

Use the room sensor preset, double the wake interval, and explain which current contribution changes.

Practice 2

Choose the BLE beacon preset and lower sleep current. Notice when sleep dominates lifetime.

Practice 3

Select CR2032 with a high radio current and check whether peak-current margin becomes the limiting factor.

Related Study

Battery Discharge Curve See how voltage, cutoff, and knee region affect usable capacity. Power Budget Calculator Compare device states and find the biggest current cost. Energy Harvesting Cycle Explore when harvested energy can extend battery life.