nRF52 'online power profiler' battery life calculation check

RE: nRF52 'online power profiler' battery life calculation check

Roger — Wed, 18 Jan 2017 14:00:29 GMT

That is absolutely awesome! Thanks for the great answer.

RE: nRF52 'online power profiler' battery life calculation check

Jørgen Holmefjord — Wed, 18 Jan 2017 13:55:57 GMT

To clarify, the online power profiler reports the average current consumption of the device from the given settings. If you input a connection interval of 2s, the 5.4 µA returned includes the sleep current between events (System On IDLE in the table). If this is the connection interval you will have, the device will on average consume 5.4 µA, or 16.2 µW with a 3 V battery. This will give a battery life estimate of 4.44 years (not so far from your last calculation).

RE: nRF52 'online power profiler' battery life calculation check

Roger — Wed, 18 Jan 2017 13:21:04 GMT

Hi Jørgen,

Thank for the quick response.

For advertising I set the BLE interval to 10.24 seconds which equaled 3.5uA. Please see the following image: nRF52 Advertising - Current Consumption Example.png

For a peripheral connection I set the BLE interval to 2 seconds which equaled 5.4uA. Please see the following image: nRF52 Peripheral connection - Current Consumption Example.png

The power consumption is now significantly less. You're saying once the slave advertises and pairs/bonds with the master, devices must communicate between a minimum and maximum interval of 7.5ms to 4s in order to keep the connection alive.

The way I understand then the power consumption is as follows: (neglecting the advertising current consumption, this I assume will only happen once till a connection is established with the master)

Radio power consumption = (5.4uA * 3V) * 1/2s = 8.1uW

System power consumption = (2uA * 3V) = 6uW (Assuming RTC running and I have RAM retention)

Total power consumption = 14.1uW

Battery life = ( (300mAh * 3V) / 14.1uW ) * 0.7 = 44681 hrs = 1860 days

I hope I'm on the right track?

Kind regards,

Roger

RE: nRF52 'online power profiler' battery life calculation check

Jørgen Holmefjord — Wed, 18 Jan 2017 12:13:26 GMT

Why are you multiplying by 1/60?

P = U * I => 161 µA * 3 V = 483 µW

This should give approximately 54.35 days with your battery.

[EDIT:] Maybe you divided by 60 since you mentioned you wanted to send once a minute. If you are in a connection, the devices will need to communicate more often to keep the connection active. The max connection interval is 4 s. From the image you provided it looks like you have calculated the power for advertising. It is possible to set an advertising interval of up to 10.24 s.

Best regards,

Jørgen