Battery life estimator
List what your device does, how much current each mode draws, and how often. The estimator works out the average current and battery life, and shows which mode is using up the battery, so you know where to spend effort.
Estimate
Battery life
–
Average current
–
Where the charge goes
How the estimate works
This is the power budget described in Battery-powered design. Each activity’s current is weighted by its share of the time, the device sleeps for the rest, and always-on drains and self-discharge are added throughout. Usable capacity divided by the average current gives the battery life.
- Activities are assumed not to overlap. If two run at once, enter them as one activity with their combined current.
- Self-discharge is treated as a steady drain, a share of rated capacity each year. The typical figures are for room temperature; self-discharge rises with heat.
- For a rechargeable battery, the result is the time between charges.
- The battery and regulator must also deliver the peak current without the voltage dropping too far. An average tells you nothing about that.
An estimate, not a measurement
Use the estimate to find where the charge goes and to compare options early. Then measure real hardware over many wake cycles, including rare events such as reconnects and retries, and at the ends of your temperature range. Put the measured numbers back into the budget, and find out why wherever they disagree.
Want a second look at your power budget?
If you are planning a battery-powered product and want a second look at the power budget or the measurement plan, get in touch.
Based in southern Indiana. Working with clients anywhere.