battery life estimate

[Ridhi]

i have nrf52832 using nrf sdk version_17 and s132.

I have application for logging

i have followed steps:

1). intially device in sleep mode

current: 0.35 micro Amp

2). press button for 5 sec and then device advertises for 30 secs: 

current: 84.29 micro Amp

3). connect on nrf connect app for mobile

displays services and characteristics 

current: 740.40 micro Amp

4). chip erase 5 secs: 14.81 mA

5). takes about 100 logs in interval of 2 secs

each log: 7.03mA 

amidst logs: 2.11 micro Amp

so total 100 logs almost take 3min 22 secs and current: 1.57mA

6). disconnect and then advertise and connect and notify enable to get data: 

data log getting current: 741.20 micro Amp for 52 seconds

I am using coin cell battery CR2450 LITHIUM 3V

attaching power profiler trace.

pls help to calculate the life of device

[Karl Ylvisaker]

Hello,

It seems you did not include any power profiler trace. Either way, to estimate the battery life of your device you will need to measure the average power draw and duration of the operations that the device will wake up to execute, in addition to calculating the sleep current.
In essence, create an estimate for the total average power draw of your device.
Then, you check this average power draw against the typical capacity for the battery you have chosen - this will be listed in the specific battery's datasheet.

Best regards,
Karl

[Ridhi]

karl i am not able to attach the trace of ppk .i am using insert option but it is not helping

[Karl Ylvisaker]

That is strange - I have had no problem with this in the past, and I tested this just now on my end by uploading an entire SDK as a .zip file without issues.
Are you getting any error messages or warnings when you do this? Does the upload being after you have selected the file?

Either way, I do not think you will need to upload the trace to make this estimate, since I would need to know a lot more about the regular operation of the device before I would be able to make any estimates myself.

Therefore, I suggest that you make the estimates as described earlier and compare them with the capacity of the specific battery you intend to use, to estimate the battery life of your device.

Best regards,
Karl

[Ridhi]

ppk-20220118T084110-data-logger.rar

[Ridhi]

i have shared you the trace:

functions:

1). unconnected: giving about 0.35 micro amp

2). press button for 5 secs: advertise for about 30 seconds with adv interval as 2000ms

3). connect on nrf connect app for desktop connection interval 1000-1000ms

4). press button for 5 secs put device in data logging mode take about 96 logs each of 29 bytes after 2 secs interval

5). press button and put device to sleep mode giving about 0.35 micro amp again

6). again press button for 5 sec and put in advertise mode

7). connect on app and enable a notification and get data 

CR2450 lithium 3v battery life has to be estimated

[Ridhi]

gentle reminder

[Karl Ylvisaker]

Hello again, Ridhima

As mentioned, it is hard for me - or anyone else - to make any prediction about the battery life of your device based on the provided information.
For starters; while you have detailed the different functions and operation of your device, you have not mentioned anything about how frequent or many of these wake-ups you will have, or how long it will remain in the connected state, etc.

I suggest that you use the PPK II to make some predictions on what the average current consumption will be for the duration of one of these button-logging-connection scenarios will be, then make an estimate for how often this scenario will happen, measure the average current while in-between these scenarios, and then finally calculate how much of its time total will be spent in the power-draw scenario, and how much will be spent in sleep.

To illustrate this, say that the average current consumption during the button-logging-connection scenario is 1 mA, and that the sleep current (in-between scenarios) is 50 µA. Lets also assume a battery capacity of 220 mAh.
If you estimate that each scenario lasts for 1 minute, and that it on average happens once every hour, you will have an overall power consumption of ~66 µA.
If your battery has a capacity of 220 mAh, the battery life expectancy is 220 mAh divided by 66 µA, which yields roughly 3333 hours, or ~140 days.

Now, do the same calculations with the numbers you estimate for your device, to estimate the battery life expectancy for the device.

Best regards,
Karl

[Ridhi]

Hello karl,

i hav shared you the power profiler trace and battery is CR2450 

1). at first my device is in unconnected mode for 15 secs giving average current 0.35 micro amp for window selected

2). then i press button for 5 secs it gives about 6.48mA 

3). the device then goes into advertsisng state. giving current  84.29 micro Amp

max the device can advertise for 3 mins

4). then with 1000ms connection interval set the sevice and charactersitics are displayed for say about 30 seconds 

5). then we take about 100 logs after 2secs interval :1 log takes 6.38mA current

6). then press button for 5 secs and then get the data after connection mode using notification

Maximum i can set to get 16000 logs and the durstion between logs can be set max to 10 mins.

Snips.rar

[Karl Ylvisaker]

Ridhima, please read my previous reply thoroughly.
You have shared this same information with me multiple times - I have acknowledged this - but it is impossible to make an estimate on battery life expectancy without any notion of how frequent the scenario you describe will occur.

I have provided you with all you need to conduct these calculations yourself, I recommend that you do so instead of providing me the scenario details yet again.

Best regards,
Karl

[Ridhi]

Basically i have a temperature humidity SHT40 sensor, winbond nor 2MB flash and nrf52832 ble dev kit. I am taking about 100 readings from SHT40 sensor ie 12bytes  after 2 seconds interval. Then storing it in flash and able to read over nrf connect using notification enable.

Karl i am finding difficulty in battery estimation actually I have shared you with details about 1 complete scenario how all steps are followed by the user.

[Karl Ylvisaker]

Thank you for elaborating, but you are still not answering my questions.
How often does it happen? How often will the button be pressed and the readings performed?
This is paramount to perform any sort of estimate of the battery life. Will it happen once every day, once every hour, or once every minute?
How long will each typical connection last?

Please read my previous replies again. Try to make a calculation following the method I outlined on your own, and show them to me. Calculate the average current draw for a complete scenario, along with the current draw during sleep. Calculate how much of the time the device will spend in the current draw scenario, and how much of the time it will be sleeping. Then, make an average for the overall current draw and calculate how many hours your battery will last under this load.

Best regards,
Karl