CR2032 Coin Cell battery life estimation with NRF52 as beacon

RE: CR2032 Coin Cell battery life estimation with NRF52 as beacon

Einar Thorsrud — Tue, 31 Jul 2018 08:06:12 GMT

OK, so you are only really interested in the properties of the battery itself? Then the article High pulse drain impact on CR2032 coin cell battery capacity which you linked to is probably the best description Nordic have. I do not see the big advantage of testing this yourself as you can refer to articles like these, but if you want to, you would have to set up a similar test, drawing large amount of current for short durations of time. You can accelerate the test by shortening the time between the current consumption peaks. If you want to do this without special firmware you could set the beacon advertising interval to 20 ms (minimum allowed except for time limited direct advertising), but that would still mean that a test could run for a couple of week before the coin cell battery (220 mAh) is depleted.

RE: CR2032 Coin Cell battery life estimation with NRF52 as beacon

Madhav Aggarwal — Tue, 31 Jul 2018 07:18:40 GMT

Hello Mr. Thorsrud,

Thank you for your prompt reply. Actually, we have already measured our current profile using an oscilloscope as described in Measuring Current Chapter and got average current and time duration for our own specific application. Then we used that value to calculate theoretical CR2032 battery's lifetime according to the formula as mentioned in the Case ID 121570:

Battery hours = (Battery Capacity/Avg current drawn)*0.7

But, as we know that CR2032 coin cell's full capacity(220mAH) can be achieved if current drawn is less than 500 µA, and battery life degrades when peak current of order ~15mA is drawn, as in case of NRF52. So, is there any way practically determine CR2032's battery life with peak currents by performing some experiment?

P.S. we also referred to Nordic's document to find a solution but didn't find something that we can apply to our case

Thank you,

Madhav

RE: CR2032 Coin Cell battery life estimation with NRF52 as beacon

Einar Thorsrud — Tue, 31 Jul 2018 06:26:05 GMT

Hi Madhav,

You can refer to the Measuring current chapter in the nRF52 DK documentation for details about how to measure current consumption. You need to measure the current consumption during development as well, to verify that the current consumption is as expected. We often see customer projects with too high current consumption, typically caused by how the nRF is used (such as not disabling peripherals that are not needed, keeping HFCLK running etc.) or other components on their custom PCB drawing a lot of current.

I recommend you also use the nRF52 Online Power Profiler to find the power consumption of the nRF52 beacon. This is uses a model that is based on extensive testing and measurements, and results are typically within 5%. Then you compare that with the data you have from your battery to find the expected battery life of your device.