Battery Life & Current Consumption Calculator

How to estimate battery life for an embedded device

Battery-powered boards spend most of their time asleep and wake up briefly to measure, compute and transmit. Battery life depends on the average current over that whole schedule, not on the current in any single state. The calculator builds that average from your actual power tree:

1. States (Battery tab): list the phases of the schedule, such as Sensing, Radio TX and Deep sleep, with a duration each. The schedule repeats over a 24 h day, a 7-day week or a custom cycle such as a 90 s wake/sleep loop, and durations can be given per cycle, per hour, per day or per week. Mark one state, usually sleep, as fills remainder.
2. Rails: add every regulator output, its type (switching or linear), efficiency and quiescent current per state. Rails can feed other rails and can be switched off in selected states.
3. Loads: add each part from the built-in library or as a custom load, assign it to a rail and enter its current in every state. Use the count field for repeated parts.
4. Battery: choose a chemistry and capacity or an external supply, and optionally solar charging.

The Results tab shows average and peak current, per-rail and per-state breakdowns, battery life and a state-of-charge chart. The Topology tab draws the power tree. The step-by-step guide walks through a full example. Compact mode is free; Full mode, with the accuracy and solar models, scenario comparison and the PDF report, is part of Calculator Pro.

Formulas

• Rail output current: I_out = Σ(load current × count) + child rails' input current + rail quiescent current
• Switching rail: I_in = V_out × I_out / (V_in × η). Linear rail: I_in = I_out
• Average current: I_avg = Σ(I_state × t_state) / T_cycle
• Solar (24 h average): I_solar = I_charge × sun hours / 24, reduced by the charge controller's efficiency and quiescent draw in Full mode
• Battery life: t = C_effective / (I_avg − I_solar). If solar covers the load, the design is reported as energy-sustained.

Limits

• It is an average-current model. Capacity is taken in mAh with no discharge curve or cut-off voltage, and the state-of-charge chart is linear.
• Regulator efficiency is one number per rail; it does not change with load.
• Peak current is only shown for loads where you enter a peak. The tool does not predict inrush or radio bursts.
• Solar uses the daily sun hours you enter. The Solar Pro Pack adds worst, average and best month from a climate zone, but panel angle, shading and weather are still up to you.

Frequently asked questions