IoT Battery Life & Power Budgets: Duty Cycles, Sleep Current & Energy Harvesting

What you'll build

What you will be able to do

Each lab ends with a concrete result that you build yourself and the checker confirms, cell by cell.

• Compare five battery options for the fictional Fernleaf FN-200 sensor node in mWh and Wh, convert µA to mA and find how many days each lasts at a constant 25 µA.
• Turn the FN-200's state table (sleep, sensor, MCU, radio) into the charge per cycle, the average current in µA and the share each state takes from the battery.
• Estimate the FN-200's battery life in three climates, first ideally (mAh ÷ mA), then realistically with temperature derating, the cut-off voltage and self-discharge.
• Calculate the charge and energy of one FN-200 message at six radio profiles, the average current it adds at 4 messages per hour, and how many messages per day fit a fixed radio budget.
• Build the table every product manager asks for: battery life of the FN-200 at sampling intervals from 1 to 120 minutes, find the shortest interval that still reaches 5 years and chart the curve.
• Check whether five batteries can feed the FN-200's 120 mA radio burst without the voltage collapsing below 2.4 V, at room temperature and in the cold, and find the coin cell's real current limit.
• Check month by month whether a 30 mW solar cell can run the cellular FN-200 variant, find the winter deficit and size the energy buffer it needs.
• Plan battery swaps for 1,500 FN-200 nodes at six customer sites: a planned replacement interval with a safety margin, replacements per year, the annual cost and the cost per node per year.