nRF52 battery consumption estimate

[Mufasa1]

Hi guys, I am trying how figure out the the devzone.nordicsemi.com/.../ works or ecuations to estimate the battery life using a central module.

My central device is battery powered and it goes from deep sleep to active each 10mins transmitting a Write to a peripher 20bytes and an indicate to the central 12bytes size. The connection time is about 50ms and the peripheral advertising interval is 20ms.

I am trying to calculate it in the following way:

RF transmitting = 8.1mA RF listening = 6mA

A average RF transmitting/reciving is 7mA per sec using DCDC enabled Sleep mode is 4uA per sec

estimate RF activity = ( 7mA x 0.05s)

Estimate Sleep mode consuption = 4uA x 3600s x 10s)

Estimate consumption = Estimate RF activity + Estimage Sleep mode consumption

Estimate Battery life = battert capacity / estimate cosumption

Is iit a correct way to estimate the battery life?

Thanks.

[Hung Bui]

I forgot to ask if you measured the RTC current to count the time the board in sleep mode ? 4uA is included the RTC or not ? Have you tried to check in the datasheet if 4uA match with what stated there ?

My calculation for your setup would be: We assume it would take 100ms for scanning before the connection can be established, it could be smaller.

Current consumption = (7mAx0.1s + 0.735mA (as in the online calculator for peripheral, similar value can be used for central) 0.05s + 0.004mA(600s-0.15s) )/ 600s = 0.0041215 mA.

The estimated battery life will be 240mAh/0.0041215mA = 58231 h = 2426 days. Given other factors such as temperature, current leakage, self discharge over time, you should use 70% of this estimation, meaning around 1698 days.

You can see that the most important number is the sleeping current, if you can reduce sleeping current you can improve battery life a lot. Next factor is the peak current. I would suggest you to have a look at this interesting article made by one our staff: m.eet.com/.../c0924post.pdf