battery level in sdk12.1.0

[mani]

Hi team,

iam using sdk 12.1.0 (ble_app_beacon) I want to advertise the battery percentage.Right now iam using the nrf dongle(it doesn't have cell coin battery) and flashing the ble_app_beacon.does it advertise the battery percentage?? if it capable, where can i view the battery level.or is there any app or sdk to advertise battery level with uuid and it's information.please send me the information if possible,thanks in advance.

[Alex]

One of the options is to include in Advertising packet manufacturer specific data advdata.p_manuf_specific_data with one byte of battery state but it is not standard. Also need to make sure it is refreshed when battery state changed.

[mani]

k i able advertise data .can u please tell me how to get battery state from ble_app_beacon ??

[AmbystomaLabs]

On our product we weren't using Major/Minor UUID and just used a byte of this to send battery info. This way we didn't add to the payload length and the smartphone API's already passed through major and minor data.

[Sigurd]

Hi,

In order to get the battery percentage you will need to use the ADC to read the battery voltage, and then convert it into battery percentage using the battery's discharge curve. This is done in e.g. the ble_app_proximity example. This example does not advertise the battery percentage, but uses the Battery Service to send the battery percentage to a central that have connected to the peripheral.

[AmbystomaLabs]

I also recommend you include the ambient temp in your percentage calculations. You will notice on the battery curves a strong temp dependence on nominal voltage. If you are just doing some occasional work with the processor (for example sending out beacons) you can safely use the processor temp as ambient. My tests have shown it to be always within 2C of ambient when just sending out beacons every second. And be aware of when you are measuring the voltage. Button cells have high internal resistance and odd chemistry. After bouts of processor activity they will show low by several hundred millivolts for a few minutes. For this reason I never measure battery voltage immediately after boot, radio activity or LED activity.