nRF52832 2xL91 battery level fluctuation

[gdb]

Hi, 

I am using 2xL91 battery for powering board with sensor and camera. In general there is no fluctuation when we use sensor which is taking about 4.2mA and in idle mode it is taking less than 1mA. 

But when going to power ON(280mA) the camera for short(2-3 sec), and reading battery voltage before that it shows battery goes below from 3.0v and than come back to same and sometimes repeat

below is the nRF 52832 ADC input

reading with predefined functions from nrf_drv_saadc_sample()

saadc resolution is 14

settings are default  

#define NRF_DRV_SAADC_DEFAULT_CONFIG                                        \

    {                                                                       \

    .resolution         = (nrf_saadc_resolution_t)SAADC_CONFIG_RESOLUTION,  \

    .oversample         = (nrf_saadc_oversample_t)SAADC_CONFIG_OVERSAMPLE,  \

    .interrupt_priority = SAADC_CONFIG_IRQ_PRIORITY,                        \

    .low_power_mode     = SAADC_CONFIG_LP_MODE                              \

    }

 

below is the fluctuation sample 

[Karl Ylvisaker]

Hello,

I am using 2xL91 battery for powering board with sensor and camera. In general there is no fluctuation when we use sensor which is taking about 4.2mA and in idle mode it is taking less than 1mA. 

But when going to power ON(280mA) the camera for short(2-3 sec), and reading battery voltage before that it shows battery goes below from 3.0v and than come back to same and sometimes repeat

I am not sure that I understand exactly what you mean by this. What do you mean when you say 'the camera for short (2-3 sec)'?
Are you saying that you are seeing readings as expected during operation, but that the samples taken around device startup is fluctuating?
Are these tests done on fresh batteries, or have they been in use for a while already? - more so, could it be that one of the batteries is in poor health, while the other is not?
Do you know the total current draw during startup of the device?

Looking forward to resolving this issue together!

Best regards,
Karl

[gdb]

Hi, thanks for the reply 

By meaning  'the camera for short (2-3 sec)' means we power ON Camera for image capture for short duration of 2-3 sec 

Yes, batteries are fresh one and its Enerzier L91 

 Total current is in idle mode(no operation just advertising) is less than 1mA 

Total current when Sensor is powered ON is about 4.2mA 

Total current when  going for image capture is around 280mA 

Karl Ylvisaker said:

Are you saying that you are seeing readings as expected during operation, but that the samples taken around device startup is fluctuating?

Yes, right

[gdb]

i am sorry not the startup but when going for image capture

[Karl Ylvisaker]

Hello,

gdb said:

thanks for the reply

No problem at all gdb, I am happy to help!

gdb said:

Yes, batteries are fresh one and its Enerzier L91 

Thank you for clarifying - I've found this datasheet which I assume is the one in question, is this correct? 

gdb said:

 Total current is in idle mode(no operation just advertising) is less than 1mA 

Total current when Sensor is powered ON is about 4.2mA 

Total current when  going for image capture is around 280mA 

Just to rule out any potential sources of error, could you elaborate on how you are doing your power consumption measurements? Are you working on a nRF52 DK, or a custom board?
If you are working on the DK: could you detail how you have connected the batteries and camera to your device?
A connection diagram would be an excellent way to show this, if available.
If not, could you confirm for me if the camera uses the same power supply as the nRF52832, and if so, how is the power to the camera routed?

If I understood your latest comment correctly, you are saying that this occurs every time you are taking a picture with the camera - is this correct? If so, I suspect that the large current draw by the camera might cause the outlier sample, possibly due to the nRF52832 and camera's power routing.

Looking forward to resolving this issue together!

Best regards,
Karl