Try
Load Soil node, keep Report interval at 900 s, and press Play before changing Radio attempts.
Power Budget Calculator
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.
45.6 uA
Average load current
4.5 mWh/day
Battery energy per day
2.8 yr
Estimated runtime
1.40x
Target-life margin
Observe
Average current starts near 45.6 uA; extra Radio attempts enlarge stage charge and shorten the battery-life readout.
Explain
Each stage contributes current times duration, and repeated radio attempts add charge before battery capacity is divided by average load.
Boundary
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
--
Optimization target
--
Daily Energy by Stage
Each bar is calculated from current multiplied by total seconds per day.
Design Controls
Change one assumption at a time and watch average current, runtime, and margin update together.
Minutes between measurements or uploads.
Include regulator quiescent current and sensors left on.
MCU and support circuits while waking.
Boot, clock stabilization, and setup time.
Measurement hardware while active.
Warm-up plus conversion or sampling time.
MCU current while filtering, encrypting, or logging.
Processing time per report.
Transmit plus receive windows when the radio is awake.
Per attempt. Retries multiply this time.
Use this for retries, joins, acknowledgements, or scans.
Nameplate capacity before derating and reserve.
Voltage used by the load-side energy estimate.
Nominal voltage used to convert capacity into Wh.
Battery-side energy rises as efficiency falls.
Temperature, age, pulse load, and cutoff voltage reduce capacity.
Capacity intentionally left for margin and end-of-life behavior.
Battery loss per year before the load uses energy.
The design goal used for the margin card.
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
Radio burst: energy per delivered bit
Separate startup, useful airtime, acknowledgement listening, and expected failed attempts. Startup is paid once per reporting opportunity in this model.
Try
Start at Short reliable, then choose Fast short: current doubles while energy per delivered bit falls.
Observe
Fast short reduces TX and ACK airtime; poor delivery probability adds expected failed attempts.
Explain
State why the lower-current radio does not always win, then use Fast long range to explain why the crossover is conditional.
TX airtime
ACK airtime
Success by cap
Expected attempts
Startup energy
Energy per attempt
Opportunity energy
Energy / delivered bit
1. Startup
2. Transmit
3. Receive / ACK
4. Retry expectation
Startup, paid once
First transmit
First receive / ACK
Expected failed attempts
Technical boundaries. Delivery probability is an entered independent per-attempt value. The model does not derive RF success from distance, path loss, modulation, coding, interference, fading, collisions, temperature, battery voltage sag, or protocol-specific retry timing. It excludes idle listening and regulatory off-time unless represented in the entered startup/RX terms. Validate with packet traces and measured current.
Ownership boundary. This calculator owns energy and expected delivery cost. The Duty-Cycle Calculator owns regulatory airtime/off-time and fleet collision pressure; it consumes TX airtime but does not reproduce energy per bit. The Sleep Mode Optimizer owns sleep/wake policy. In this model startup is paid once per reporting opportunity; a real protocol may pay it again per retry.
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.