A battery-life estimate is an assumption, not a promise.
Duty-cycle maths is useful early in a connected-product project. It becomes dangerous when a simplified estimate is mistaken for measured field performance.
The basic planning model
A simple estimator weights active current and sleep current by the amount of time the device spends in each state. That average current can be compared with usable battery capacity to produce a planning estimate.
Why usable capacity is not nameplate capacity
Battery chemistry, temperature, discharge rate, regulator behaviour, age and the minimum voltage required by the device can all reduce usable capacity. A planning model should therefore include deliberate derating and reserve margin.
Radio behaviour can dominate
Retries, poor coverage, network attachment, scanning and longer-than-expected transmission windows can make the real active-energy profile very different from the ideal cycle entered into a spreadsheet.
Sleep current deserves measurement
For long-lived devices, small unexpected currents can become material because they persist for most of the product's life. Debug interfaces, sensors, regulators and peripherals that do not enter their intended low-power state can destroy an otherwise attractive estimate.
Connect battery assumptions to field economics
A battery interval is also a maintenance interval. If a change from 36 months to 18 months creates an extra site visit across thousands of devices, the commercial impact can outweigh the battery cost itself.
Model the commercial side too
Fleet Economics Pro connects a simplified battery view with fleet cost, field failure, telemetry and recurring revenue assumptions.
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