1. Start with a known device
Pick a preset that behaves like the node you are designing. The first estimate should be simple and visible.
Power Budget Calculator
Build an IoT power budget from sleep current, short active bursts, radio time, battery derating, and target lifetime.
animation
energy
power
battery
duty-cycle
hardware
intermediate
A learner-ready power budget workbench with duty-cycle timeline animation, stage energy breakdown, battery derating, efficiency, margin checks, formula trace, and technical accuracy notes.
Animation
Power Budget
Duty Cycle
Battery Life
Power Budget Calculator
A power budget turns tiny sleep currents and short radio bursts into one daily energy number. Change the design, watch the duty cycle move through a compressed day, and decide which part deserves engineering effort first.
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Average load current
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Battery energy per day
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Estimated runtime
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Target-life margin
2. Watch one reporting cycle
The timeline is time-compressed so short wake, sense, process, and transmit stages can be seen clearly.
3. Compare stage energy
The bars show mAh per day. The largest bar is usually your first optimization target.
4. Check the battery side
Efficiency, temperature derating, reserve, and self-discharge can change a good load estimate into a poor field estimate.
Sleep
Most of the calendar time is spent here.
--Wake
Clock startup and sensor power-up.
--Sense
Measurement hardware is active.
--Process
MCU formats and validates the reading.
--Radio
Transmit, receive, join, or retry cost.
--Duty-Cycle Energy Timeline
Use Play or Step to follow one reporting cycle. Bar lengths below the timeline are based on daily energy, not visual stage width.
Sleep
MCU
Radio
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Optimization target
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Daily Energy by Stage
Each bar is calculated from current multiplied by total seconds per day.
Convert each current burst into daily charge.
mAh/day = current_mA x seconds_per_day / 3600
Average current is daily charge spread over 24 hours.
I_avg = total_mAh_per_day / 24
Efficiency matters when converting load energy to battery energy.
Wh/day = load_mAh_day x rail_V / 1000 / efficiency
Usable battery energy is nameplate capacity after derating and reserve.
days = usable_battery_Wh / battery_Wh_per_day
Power Budget Quick Reference
What average current means
- It is the charge used in one day divided by 24 hours.
- It is not the peak current seen by the battery or regulator.
- A short high-current radio burst can still matter if it happens often.
What to include
- MCU wake and processing current.
- Sensor warm-up and conversion time.
- Radio TX, RX, scans, joins, acknowledgements, and retries.
- Regulator quiescent current and sensors left powered during sleep.
Common early mistakes
- Using ideal battery capacity at room temperature.
- Forgetting radio receive windows or cellular attach time.
- Assuming sleep current is zero.
- Ignoring peak-current limits and voltage sag.
Technical Accuracy Notes
mAh and Wh are not interchangeable
mAh is charge at a voltage. This animation calculates load mAh/day, converts it to load Wh/day at the selected rail voltage, then divides by regulator efficiency to estimate battery Wh/day.
Battery capacity is conditional
Nameplate capacity depends on chemistry, temperature, discharge rate, cutoff voltage, aging, and pulse load. The derating and reserve controls are first-order correction factors, not substitutes for a datasheet and lab test.
Peak current still matters
A device can have a low average current but still fail if the battery or regulator cannot supply radio peaks without voltage droop. Check peak current separately from lifetime.
Practice Challenges
Challenge 1: Make sleep matter less
- Start with the leaky design preset.
- Reduce sleep current until radio becomes the dominant bar.
- Explain why lowering active time alone did not fix it first.
Challenge 2: Hit a two-year target
- Start with the soil node preset.
- Set target lifetime to 24 months.
- Try longer intervals, fewer retries, or a larger battery.
Challenge 3: Explain a failed estimate
- Set derating to 45 percent and efficiency to 55 percent.
- Compare load-side average current with battery-side energy.
- Identify why a simple mAh estimate can overpromise runtime.
Battery Life Estimator
Go deeper into battery drain curves, self-discharge, target life, and charge per wake cycle.
Sleep Mode Optimizer
Compare idle, light sleep, deep sleep, and hibernate against wake latency and duty cycle.
Power Profile Analyzer
Inspect measured current profiles and find which phase consumes the most energy.