Battery Life Calculator

A battery never delivers its printed capacity, so dividing milliamp hours by milliamps gives a ceiling rather than a runtime. Enter the capacity, the current the device draws and a derating factor for self discharge, cold and the cutoff voltage, and the tool returns the life in hours and days. The second action is for anything that wakes, does something and sleeps: give it the active current, how long the burst lasts, how often it happens and the sleep current, and it returns the average draw and the life in days and years. Everything is in charge and current, the units small devices are specified in, so no cell voltage is needed.

Calculator Type
Capacity Unit
Current Unit

A constant draw: a torch, a radio, a motor, anything that is simply on.

The figure printed on the cell or the pack. A CR2032 coin cell is about 220 mAh, an AA alkaline about 2500, an 18650 lithium cell 2500 to 3500.
What you expect to actually get out. 100 takes the label at face value, which no cell delivers. 80 to 90 is a normal allowance for self discharge, the cutoff voltage and ordinary temperatures.
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Capacity Unit

A sensor, a tracker or a remote that wakes, does something and goes back to sleep. The sleep current usually decides the answer.

The figure printed on the cell or the pack. A CR2032 coin cell is about 220 mAh, an AA alkaline about 2500, an 18650 lithium cell 2500 to 3500.
The draw during the burst, including the radio if it transmits.
How often the device wakes. Once a minute is 60, once an hour is 3600, once a day is 86400.
Deep sleep is usually quoted in microamps, so divide by 1000 to get milliamps. 50 uA is 0.05 mA.
What you expect to actually get out. 100 takes the label at face value, which no cell delivers. 80 to 90 is a normal allowance for self discharge, the cutoff voltage and ordinary temperatures.
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