Use this battery life calculator to find out how long a battery will last in your circuit.
Battery capacity is given in milliamp-hours (mAh). A 2000 mAh battery could, in theory, give 2000 mA for one hour, or 20 mA for 100 hours:
- Average current
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- Battery life
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- In hours
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How to Use It
Pick your battery, or type in the capacity from its datasheet. Then fill in how much current your circuit uses. You can measure it with a multimeter in series with the battery.
If your circuit sleeps most of the time, like a sensor that wakes up to take a reading, tick the box. Then fill in the current when it’s awake and when it’s asleep, and how much of the time it’s awake.
In practice, you don’t get the full capacity out of a battery, especially at high currents or in the cold. That’s why the calculator only counts 80% of it by default. Read more about why the battery voltage changes.