Estimate IoT sensor battery life from usable capacity and a duty-cycle power profile. Sleep current, active current, transmission duration, reporting interval, capacity derating, and annual self-discharge are converted into average current and runtime.
Runtime is an engineering estimate based on a repeating duty cycle. The self-discharge percentage is approximated as an equivalent continuous current based on nominal capacity.
Battery chemistry, pulse-current limits, regulator quiescent current, voltage cutoff, network retries, cold temperature, and changing self-discharge can materially affect field life.
A 2,400 mAh battery derated 20% has 1,920 mAh usable. With 8 µA sleep current, 45 mA active for 2 seconds every 15 minutes, and 2% annual self-discharge, average effective current is about 0.113 mA and runtime is about 705 days (1.93 years).
Use energy-equivalent average current across the entire active event; separately verify that the battery can supply the peak.
Retries increase active time and sometimes active current, so include their average effect in the active-event inputs.
Rated capacity may not be fully usable because of temperature, aging, voltage cutoff, discharge rate, and design margin.
It is approximated as an equivalent continuous current equal to nominal capacity times the annual percentage divided by hours per year.
No. It is a duty-cycle estimate; field testing and battery monitoring are needed for maintenance planning.
| Input | Role in the estimate |
|---|---|
| Battery capacity | Rated capacity at the intended load. |
| Capacity derating | Allowance for temperature, aging, and cutoff voltage. |
| Sleep current | Average current between active events. |
| Active current | Average current while sensing and transmitting. |
| Active time per report | Total active duration in each interval. |