Power consumption fine tuning

[Sergey]

Hi everyone, Well, our device is based on NRF 51822 CFAC MCU. It’s an ibeacon based device which advertises and receives data frequently, and writes data into flash memory.
We have some power consumption issues. We need to achieve at least 200 days of autonomous device working from cr 2032 battery, so in fact you need to achieve 1 mah/24 hours energy consumption. And the main question is how to switch NRF to low power mode periodically?

[Stefan Birnir Sverrisson]

Hi Sergey

Have you looked at the nRF51 current consumption guide? There are some good pointers there on how to tune your device for minimum current consumption. Anyway, all BLE examples in the nRF5 SDK 11.0.0 let the nRF51 enter low power mode between BLE radio events.

For a connectable beacon running on nRF51, the current consumption should be:

Connectable beacon: yes    
Battery capacity: 220 mAh    
DCDC: enabled    
TX power: 0 dBm    
Advertising interval: 100 ms              //Official iBeacon advertising interval
Current consumption: ~220 uA    
Battery life: 0.22Ah / 0,000220A = 1000 hours = 41 days

Connectable beacon: yes    
Battery capacity: 220 mAh    
DCDC: enabled    
TX power: 0 dBm    
Advertising interval: 1000 ms            //Different advertising interval
Current consumption: ~25 uA    
Battery life: 0.22Ah / 0,000025A = 8800 hours = 366 days   

Connectable beacon: yes    
Battery capacity: 220 mAh    
DCDC: enabled    
TX power: -20 dBm                         //different TX power
Advertising interval: 100 ms    
Current consumption: ~173 uA    
Battery life: 0.22Ah / 0,000173A = 1271 hours = 53 days  

Connectable beacon: yes    
Battery capacity: 1000 mAh              //different battery size
DCDC: enabled    
TX power: -0 dBm                         
Advertising interval: 100 ms    
Current consumption: ~220 uA    
Battery life: 1Ah / 0,000220A = 4545 hours = 189 days

You will decrease current consumption by perhaps 10% if you have your beacon non-connectable. If you use nRF52 instead of nRF51, you will decrease current consumption by ~40% for beacons, according to the specification.

[Stefan Birnir Sverrisson]

Do you mean that your device is connected in order to receive packets, but also is advertising at the same time? Not sure about your scenario, can you describe it more?