RE: How to measure battery life time

Bjørn Kvaale — Tue, 14 Nov 2017 12:31:53 GMT

It is very difficult to measure a quickly changing current without using a very expensive multimeter. Do you have a nrf52dk at your disposal? If you do, you could upload the beacon FW to the nrf52dk & measure the current using a Nordic Power Profiling Kit. The beacon example code can be found in the SDK 14.1 under "examples/ble_peripheral/ble_app_beacon". Then, the devkit and the beacon HW should consume the same amount of current. Just make sure that you turn logging off it is turned on. Logging consumes quite a bit of current.

When you know the advertising current & the sleep current, you could average this out over a couple of minutes for example. Then, assuming that the rated coin cell battery capacity is correct, you could take the rated coin cell capacity in Ah/average current consumption in A. Then, you will get an estimate of the battery lifetime in hours.

If I were you, I would look at the datasheet for the coin cell battery and see if it specifies what discharge current they used in the discharge test to find the rated battery capacity.

For more information on discharge testing, you can look at these two devzone cases: case 1 & case 2.