IoT Sensor Node Battery Life Simulator

Radio Protocol

Report Interval

Payload size 12 B

Battery capacity 2000 mAh

Sleep current 8 µA

Live Readouts

Time on air

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Duty cycle

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Avg. current draw

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Transmits / day

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Estimated battery life

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How it works

A battery-powered sensor node spends almost all its life asleep and only wakes briefly to radio out a reading. Its average current draw is a weighted mix of the sleep current and the transmit current, weighted by the fraction of time actually spent transmitting — the duty cycle:

duty cycle   = T_air / T_interval
I_avg        = duty × I_tx + (1 − duty) × I_sleep
battery life = C_battery / I_avg

For LoRaWAN, the time-on-air T_air of one packet follows the LoRa modem's own airtime formula (used here exactly as published in Semtech's LoRa datasheet), with symbol rate set by the spreading factor SF and bandwidth BW:

T_sym       = 2^SF / BW
T_preamble  = (n_preamble + 4.25) × T_sym
n_payload   = 8 + max(ceil[(8·PL − 4·SF + 28 + 16) / (4·(SF−2·DE))] × (CR+4), 0)
T_air       = T_preamble + n_payload × T_sym

Raising SF from 7 to 12 quadruples the symbol time roughly four-fold per step, stretching every packet's airtime — and therefore its share of the duty cycle — even though the radio's transmit current barely changes with SF (it is set by TX power, not spreading factor). That's the classic LoRaWAN trade-off: higher SF buys range and penetration at the cost of airtime and battery life. NB-IoT trades a much higher transmit current for a cellular uplink; BLE trades tiny payloads and very short packets for a low-power, short-range link. The radio pulses on the node below fire in proportion to the computed duty cycle, and the gauge shows one full simulated discharge cycle compressed into a few seconds so you can watch the trend rather than wait real months for the battery to run out.

Radio pulse (transmit) Battery charge remaining

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